<?xml version="1.0" encoding="US-ASCII"?>
<!--XBRL Document Created with Wdesk from Workiva-->
<!-- -->
<link:linkbase xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <link:roleRef roleURI="http://www.southwestgas.com/role/BackgroundOrganizationAndSummaryOfSignificantAccountingPolicies" xlink:href="swx-20181231.xsd#BackgroundOrganizationAndSummaryOfSignificantAccountingPolicies" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/BackgroundOrganizationAndSummaryOfSignificantAccountingPoliciesNarrativeDetail" xlink:href="swx-20181231.xsd#BackgroundOrganizationAndSummaryOfSignificantAccountingPoliciesNarrativeDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/BackgroundOrganizationAndSummaryOfSignificantAccountingPoliciesOtherIncomeDeductionsDetail" xlink:href="swx-20181231.xsd#BackgroundOrganizationAndSummaryOfSignificantAccountingPoliciesOtherIncomeDeductionsDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/BackgroundOrganizationAndSummaryOfSignificantAccountingPoliciesPolicies" xlink:href="swx-20181231.xsd#BackgroundOrganizationAndSummaryOfSignificantAccountingPoliciesPolicies" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/BackgroundOrganizationAndSummaryOfSignificantAccountingPoliciesScheduleOfCapitalizedAndDebtPortionOfAfudcDetail" xlink:href="swx-20181231.xsd#BackgroundOrganizationAndSummaryOfSignificantAccountingPoliciesScheduleOfCapitalizedAndDebtPortionOfAfudcDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/BackgroundOrganizationAndSummaryOfSignificantAccountingPoliciesScheduleOfEarningsPerShareBasicAndDilutedDetail" xlink:href="swx-20181231.xsd#BackgroundOrganizationAndSummaryOfSignificantAccountingPoliciesScheduleOfEarningsPerShareBasicAndDilutedDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/BackgroundOrganizationAndSummaryOfSignificantAccountingPoliciesScheduleOfEstimatedFutureAmortizationOfIntangibleAssetsDetail" xlink:href="swx-20181231.xsd#BackgroundOrganizationAndSummaryOfSignificantAccountingPoliciesScheduleOfEstimatedFutureAmortizationOfIntangibleAssetsDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/BackgroundOrganizationAndSummaryOfSignificantAccountingPoliciesScheduleOfGoodwillDetail" xlink:href="swx-20181231.xsd#BackgroundOrganizationAndSummaryOfSignificantAccountingPoliciesScheduleOfGoodwillDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/BackgroundOrganizationAndSummaryOfSignificantAccountingPoliciesScheduleOfOtherPropertyAndInvestmentsDetail" xlink:href="swx-20181231.xsd#BackgroundOrganizationAndSummaryOfSignificantAccountingPoliciesScheduleOfOtherPropertyAndInvestmentsDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/BackgroundOrganizationAndSummaryOfSignificantAccountingPoliciesSummaryOfIntangibleAssetsDetail" xlink:href="swx-20181231.xsd#BackgroundOrganizationAndSummaryOfSignificantAccountingPoliciesSummaryOfIntangibleAssetsDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/BackgroundOrganizationAndSummaryOfSignificantAccountingPoliciesTables" xlink:href="swx-20181231.xsd#BackgroundOrganizationAndSummaryOfSignificantAccountingPoliciesTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/BusinessAcquisitions" xlink:href="swx-20181231.xsd#BusinessAcquisitions" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/BusinessAcquisitionsNarrativeDetail" xlink:href="swx-20181231.xsd#BusinessAcquisitionsNarrativeDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/BusinessAcquisitionsScheduleOfProFormaConsolidatedFinancialInformationDetail" xlink:href="swx-20181231.xsd#BusinessAcquisitionsScheduleOfProFormaConsolidatedFinancialInformationDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/BusinessAcquisitionsScheduleOfStatementsOfIncomeOperationsDetail" xlink:href="swx-20181231.xsd#BusinessAcquisitionsScheduleOfStatementsOfIncomeOperationsDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/BusinessAcquisitionsSummaryOfFairValuesOfAssetsAcquiredAndLiabilitiesAssumedDetail" xlink:href="swx-20181231.xsd#BusinessAcquisitionsSummaryOfFairValuesOfAssetsAcquiredAndLiabilitiesAssumedDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/BusinessAcquisitionsSummaryOfFairValuesOfAssetsAcquiredAndLiabilitiesAssumedDetailCalc2" xlink:href="swx-20181231.xsd#BusinessAcquisitionsSummaryOfFairValuesOfAssetsAcquiredAndLiabilitiesAssumedDetailCalc2" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/BusinessAcquisitionsTables" xlink:href="swx-20181231.xsd#BusinessAcquisitionsTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/CommitmentsAndContingencies" xlink:href="swx-20181231.xsd#CommitmentsAndContingencies" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/CommitmentsAndContingenciesDetail" xlink:href="swx-20181231.xsd#CommitmentsAndContingenciesDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/CommonStock" xlink:href="swx-20181231.xsd#CommonStock" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/CommonStockDetail" xlink:href="swx-20181231.xsd#CommonStockDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/CommonStockTables" xlink:href="swx-20181231.xsd#CommonStockTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/ConsolidatedBalanceSheets" xlink:href="swx-20181231.xsd#ConsolidatedBalanceSheets" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/ConsolidatedBalanceSheetsParenthetical" xlink:href="swx-20181231.xsd#ConsolidatedBalanceSheetsParenthetical" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/ConsolidatedStatementsOfCashFlows" xlink:href="swx-20181231.xsd#ConsolidatedStatementsOfCashFlows" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/ConsolidatedStatementsOfCashFlowsCalc2" xlink:href="swx-20181231.xsd#ConsolidatedStatementsOfCashFlowsCalc2" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/ConsolidatedStatementsOfComprehensiveIncome" xlink:href="swx-20181231.xsd#ConsolidatedStatementsOfComprehensiveIncome" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/ConsolidatedStatementsOfComprehensiveIncomeCalc2" xlink:href="swx-20181231.xsd#ConsolidatedStatementsOfComprehensiveIncomeCalc2" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/ConsolidatedStatementsOfEquityAndRedeemableNoncontrollingInterest" xlink:href="swx-20181231.xsd#ConsolidatedStatementsOfEquityAndRedeemableNoncontrollingInterest" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/ConsolidatedStatementsOfEquityAndRedeemableNoncontrollingInterestParenthetical" xlink:href="swx-20181231.xsd#ConsolidatedStatementsOfEquityAndRedeemableNoncontrollingInterestParenthetical" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/ConsolidatedStatementsOfIncome" xlink:href="swx-20181231.xsd#ConsolidatedStatementsOfIncome" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/Derivatives" xlink:href="swx-20181231.xsd#Derivatives" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/DerivativesAmountOfGainOrLossesRecognizedInIncomeOnDerivativesDetail" xlink:href="swx-20181231.xsd#DerivativesAmountOfGainOrLossesRecognizedInIncomeOnDerivativesDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/DerivativesFairValuesOfSwapsInConsolidatedBalanceSheetsDetail" xlink:href="swx-20181231.xsd#DerivativesFairValuesOfSwapsInConsolidatedBalanceSheetsDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/DerivativesNarrativeDetail" xlink:href="swx-20181231.xsd#DerivativesNarrativeDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/DerivativesNotionalAmountsUnderSwapsContractsDetail" xlink:href="swx-20181231.xsd#DerivativesNotionalAmountsUnderSwapsContractsDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/DerivativesPaidToAndReceivedFromCounterpartiesForSettlementsOfMaturedSwapsDetail" xlink:href="swx-20181231.xsd#DerivativesPaidToAndReceivedFromCounterpartiesForSettlementsOfMaturedSwapsDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/DerivativesRegulatoryAssetsLiabilitiesOffsettingDerivativesAtFairValueInCondensedConsolidatedBalanceSheetsDetail" xlink:href="swx-20181231.xsd#DerivativesRegulatoryAssetsLiabilitiesOffsettingDerivativesAtFairValueInCondensedConsolidatedBalanceSheetsDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/DerivativesSummaryOfFinancialAssetsAndLiabilitiesAtFairValueDetail" xlink:href="swx-20181231.xsd#DerivativesSummaryOfFinancialAssetsAndLiabilitiesAtFairValueDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/DerivativesTables" xlink:href="swx-20181231.xsd#DerivativesTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/DocumentAndEntityInformation" xlink:href="swx-20181231.xsd#DocumentAndEntityInformation" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/IncomeTaxes" xlink:href="swx-20181231.xsd#IncomeTaxes" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/IncomeTaxesAdditionalInformationDetail" xlink:href="swx-20181231.xsd#IncomeTaxesAdditionalInformationDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/IncomeTaxesDeferredTaxAssetsAndLiabilitiesDetail" xlink:href="swx-20181231.xsd#IncomeTaxesDeferredTaxAssetsAndLiabilitiesDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/IncomeTaxesDeferredTaxAssetsAndLiabilitiesDetailCalc2" xlink:href="swx-20181231.xsd#IncomeTaxesDeferredTaxAssetsAndLiabilitiesDetailCalc2" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/IncomeTaxesReconciliationOfUSFederalStatutoryRateToConsolidatedEffectiveTaxRateDetail" xlink:href="swx-20181231.xsd#IncomeTaxesReconciliationOfUSFederalStatutoryRateToConsolidatedEffectiveTaxRateDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/IncomeTaxesReconciliationOfUnrecognizedTaxBenefitsDetail" xlink:href="swx-20181231.xsd#IncomeTaxesReconciliationOfUnrecognizedTaxBenefitsDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/IncomeTaxesSignificantComponentsOfDeferredIncomeTaxExpenseBenefitDetail" xlink:href="swx-20181231.xsd#IncomeTaxesSignificantComponentsOfDeferredIncomeTaxExpenseBenefitDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/IncomeTaxesSummaryOfIncomeBeforeTaxesAndNoncontrollingInterestForDomesticAndForeignOperationsDetail" xlink:href="swx-20181231.xsd#IncomeTaxesSummaryOfIncomeBeforeTaxesAndNoncontrollingInterestForDomesticAndForeignOperationsDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/IncomeTaxesSummaryOfIncomeBeforeTaxesForContinuingAndDiscontinuedOperationsDetail" xlink:href="swx-20181231.xsd#IncomeTaxesSummaryOfIncomeBeforeTaxesForContinuingAndDiscontinuedOperationsDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/IncomeTaxesSummaryOfIncomeTaxExpenseBenefitDetail" xlink:href="swx-20181231.xsd#IncomeTaxesSummaryOfIncomeTaxExpenseBenefitDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/IncomeTaxesTables" xlink:href="swx-20181231.xsd#IncomeTaxesTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/LongTermDebt" xlink:href="swx-20181231.xsd#LongTermDebt" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/LongTermDebtEstimatedMaturitiesOfLongTermDebtDetail" xlink:href="swx-20181231.xsd#LongTermDebtEstimatedMaturitiesOfLongTermDebtDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/LongTermDebtNarrativeDetail" xlink:href="swx-20181231.xsd#LongTermDebtNarrativeDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/LongTermDebtScheduleOfCarryingAmountsAndEstimatedFairValuesOfLongTermDebtDetail" xlink:href="swx-20181231.xsd#LongTermDebtScheduleOfCarryingAmountsAndEstimatedFairValuesOfLongTermDebtDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/LongTermDebtSummaryOfEffectiveInterestRatesOnVariableRateIdrbsDetail" xlink:href="swx-20181231.xsd#LongTermDebtSummaryOfEffectiveInterestRatesOnVariableRateIdrbsDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/LongTermDebtTables" xlink:href="swx-20181231.xsd#LongTermDebtTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/OtherComprehensiveIncomeAndAccumulatedOtherComprehensiveIncomeAoci" xlink:href="swx-20181231.xsd#OtherComprehensiveIncomeAndAccumulatedOtherComprehensiveIncomeAoci" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/OtherComprehensiveIncomeAndAccumulatedOtherComprehensiveIncomeAociAmountRecognizedBeforeIncomeTaxAssociatedWithDefinedBenefitPlansInAccumulatedOtherComprehensiveIncomeDetail" xlink:href="swx-20181231.xsd#OtherComprehensiveIncomeAndAccumulatedOtherComprehensiveIncomeAociAmountRecognizedBeforeIncomeTaxAssociatedWithDefinedBenefitPlansInAccumulatedOtherComprehensiveIncomeDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/OtherComprehensiveIncomeAndAccumulatedOtherComprehensiveIncomeAociAociRollforwardDetails" xlink:href="swx-20181231.xsd#OtherComprehensiveIncomeAndAccumulatedOtherComprehensiveIncomeAociAociRollforwardDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/OtherComprehensiveIncomeAndAccumulatedOtherComprehensiveIncomeAociNarrativeDetail" xlink:href="swx-20181231.xsd#OtherComprehensiveIncomeAndAccumulatedOtherComprehensiveIncomeAociNarrativeDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/OtherComprehensiveIncomeAndAccumulatedOtherComprehensiveIncomeAociRelatedTaxEffectsAllocatedToOciDetail" xlink:href="swx-20181231.xsd#OtherComprehensiveIncomeAndAccumulatedOtherComprehensiveIncomeAociRelatedTaxEffectsAllocatedToOciDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/OtherComprehensiveIncomeAndAccumulatedOtherComprehensiveIncomeAociScheduleOfEstimatedAmountsAmortizedFromAccumulatedOtherComprehensiveIncomeOrRegulatoryAssetsIntoNetPeriodicBenefitCostDetail" xlink:href="swx-20181231.xsd#OtherComprehensiveIncomeAndAccumulatedOtherComprehensiveIncomeAociScheduleOfEstimatedAmountsAmortizedFromAccumulatedOtherComprehensiveIncomeOrRegulatoryAssetsIntoNetPeriodicBenefitCostDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/OtherComprehensiveIncomeAndAccumulatedOtherComprehensiveIncomeAociTables" xlink:href="swx-20181231.xsd#OtherComprehensiveIncomeAndAccumulatedOtherComprehensiveIncomeAociTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/PensionAndOtherPostretirementBenefits" xlink:href="swx-20181231.xsd#PensionAndOtherPostretirementBenefits" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/PensionAndOtherPostretirementBenefitsCostOfRetirementPlanDetail" xlink:href="swx-20181231.xsd#PensionAndOtherPostretirementBenefitsCostOfRetirementPlanDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/PensionAndOtherPostretirementBenefitsNarrativeDetail" xlink:href="swx-20181231.xsd#PensionAndOtherPostretirementBenefitsNarrativeDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/PensionAndOtherPostretirementBenefitsScheduleOfAccumulatedBenefitObligationDetail" xlink:href="swx-20181231.xsd#PensionAndOtherPostretirementBenefitsScheduleOfAccumulatedBenefitObligationDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/PensionAndOtherPostretirementBenefitsScheduleOfAmountsRecognizedInBalanceSheetAndIncomeStatementDetail" xlink:href="swx-20181231.xsd#PensionAndOtherPostretirementBenefitsScheduleOfAmountsRecognizedInBalanceSheetAndIncomeStatementDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/PensionAndOtherPostretirementBenefitsScheduleOfAssumptionsUsedDetail" xlink:href="swx-20181231.xsd#PensionAndOtherPostretirementBenefitsScheduleOfAssumptionsUsedDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/PensionAndOtherPostretirementBenefitsScheduleOfExpectedBenefitPaymentsDetail" xlink:href="swx-20181231.xsd#PensionAndOtherPostretirementBenefitsScheduleOfExpectedBenefitPaymentsDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/PensionAndOtherPostretirementBenefitsScheduleOfFairValueOfPlanAssetsDetail" xlink:href="swx-20181231.xsd#PensionAndOtherPostretirementBenefitsScheduleOfFairValueOfPlanAssetsDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/PensionAndOtherPostretirementBenefitsScheduleOfNetPeriodicBenefitCostAndWeightedAverageAssumptionsDetail" xlink:href="swx-20181231.xsd#PensionAndOtherPostretirementBenefitsScheduleOfNetPeriodicBenefitCostAndWeightedAverageAssumptionsDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/PensionAndOtherPostretirementBenefitsScheduleOfNewAccountingPronouncementsDetails" xlink:href="swx-20181231.xsd#PensionAndOtherPostretirementBenefitsScheduleOfNewAccountingPronouncementsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/PensionAndOtherPostretirementBenefitsScheduleOfOtherChangesInPlanAssetsAndBenefitObligationsRecognizedInNetPeriodicBenefitCostAndOtherComprehensiveIncomeDetail" xlink:href="swx-20181231.xsd#PensionAndOtherPostretirementBenefitsScheduleOfOtherChangesInPlanAssetsAndBenefitObligationsRecognizedInNetPeriodicBenefitCostAndOtherComprehensiveIncomeDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/PensionAndOtherPostretirementBenefitsTables" xlink:href="swx-20181231.xsd#PensionAndOtherPostretirementBenefitsTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/QuarterlyFinancialDataUnaudited" xlink:href="swx-20181231.xsd#QuarterlyFinancialDataUnaudited" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/QuarterlyFinancialDataUnauditedDetail" xlink:href="swx-20181231.xsd#QuarterlyFinancialDataUnauditedDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/QuarterlyFinancialDataUnauditedTables" xlink:href="swx-20181231.xsd#QuarterlyFinancialDataUnauditedTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/ReceivablesAndRelatedAllowances" xlink:href="swx-20181231.xsd#ReceivablesAndRelatedAllowances" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/ReceivablesAndRelatedAllowancesAdditionalInformationDetail" xlink:href="swx-20181231.xsd#ReceivablesAndRelatedAllowancesAdditionalInformationDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/ReceivablesAndRelatedAllowancesScheduleOfAccountsReceivableDetail" xlink:href="swx-20181231.xsd#ReceivablesAndRelatedAllowancesScheduleOfAccountsReceivableDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/ReceivablesAndRelatedAllowancesScheduleOfAllowanceForUncollectiblesDetail" xlink:href="swx-20181231.xsd#ReceivablesAndRelatedAllowancesScheduleOfAllowanceForUncollectiblesDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/ReceivablesAndRelatedAllowancesScheduleOfPercentOfCustomersByStateDetail" xlink:href="swx-20181231.xsd#ReceivablesAndRelatedAllowancesScheduleOfPercentOfCustomersByStateDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/ReceivablesAndRelatedAllowancesTables" xlink:href="swx-20181231.xsd#ReceivablesAndRelatedAllowancesTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/RegulatoryAssetsAndLiabilities" xlink:href="swx-20181231.xsd#RegulatoryAssetsAndLiabilities" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/RegulatoryAssetsAndLiabilitiesScheduleOfComponentsOfOtherRegulatoryAssetsDetail" xlink:href="swx-20181231.xsd#RegulatoryAssetsAndLiabilitiesScheduleOfComponentsOfOtherRegulatoryAssetsDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/RegulatoryAssetsAndLiabilitiesScheduleOfComponentsOfOtherRegulatoryLiabilitiesDetail" xlink:href="swx-20181231.xsd#RegulatoryAssetsAndLiabilitiesScheduleOfComponentsOfOtherRegulatoryLiabilitiesDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/RegulatoryAssetsAndLiabilitiesScheduleOfRegulatoryAssetsAndLiabilitiesDetail" xlink:href="swx-20181231.xsd#RegulatoryAssetsAndLiabilitiesScheduleOfRegulatoryAssetsAndLiabilitiesDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/RegulatoryAssetsAndLiabilitiesTables" xlink:href="swx-20181231.xsd#RegulatoryAssetsAndLiabilitiesTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/ReorganizationImpactsDiscontinuedOperationsSolelyRelatedToSouthwestGasCorporation" xlink:href="swx-20181231.xsd#ReorganizationImpactsDiscontinuedOperationsSolelyRelatedToSouthwestGasCorporation" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/ReorganizationImpactsDiscontinuedOperationsSolelyRelatedToSouthwestGasCorporationDetail" xlink:href="swx-20181231.xsd#ReorganizationImpactsDiscontinuedOperationsSolelyRelatedToSouthwestGasCorporationDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/ReorganizationImpactsDiscontinuedOperationsSolelyRelatedToSouthwestGasCorporationTables" xlink:href="swx-20181231.xsd#ReorganizationImpactsDiscontinuedOperationsSolelyRelatedToSouthwestGasCorporationTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/Revenue" xlink:href="swx-20181231.xsd#Revenue" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/RevenueNarrativeDetail" xlink:href="swx-20181231.xsd#RevenueNarrativeDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/RevenueRevenuePerformanceObligationDetails" xlink:href="swx-20181231.xsd#RevenueRevenuePerformanceObligationDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/RevenueScheduleOfGasOperatingRevenueDetail" xlink:href="swx-20181231.xsd#RevenueScheduleOfGasOperatingRevenueDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/RevenueScheduleOfUtilityInfrastructureServicesContractsReceivableDetail" xlink:href="swx-20181231.xsd#RevenueScheduleOfUtilityInfrastructureServicesContractsReceivableDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/RevenueSummaryOfInformationAboutReceivablesDetail" xlink:href="swx-20181231.xsd#RevenueSummaryOfInformationAboutReceivablesDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/RevenueSummaryOfRevenueDisaggregatedByServiceTypeAndContractTypeDetail" xlink:href="swx-20181231.xsd#RevenueSummaryOfRevenueDisaggregatedByServiceTypeAndContractTypeDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/RevenueTables" xlink:href="swx-20181231.xsd#RevenueTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/SegmentInformation" xlink:href="swx-20181231.xsd#SegmentInformation" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/SegmentInformationAccountsReceivableForServicesDetail" xlink:href="swx-20181231.xsd#SegmentInformationAccountsReceivableForServicesDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/SegmentInformationNarrativeDetail" xlink:href="swx-20181231.xsd#SegmentInformationNarrativeDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/SegmentInformationScheduleOfRevenuesByGeographicAreaDetail" xlink:href="swx-20181231.xsd#SegmentInformationScheduleOfRevenuesByGeographicAreaDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/SegmentInformationScheduleOfSegmentReportingInformationDetail" xlink:href="swx-20181231.xsd#SegmentInformationScheduleOfSegmentReportingInformationDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/SegmentInformationTables" xlink:href="swx-20181231.xsd#SegmentInformationTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/ShareBasedCompensation" xlink:href="swx-20181231.xsd#ShareBasedCompensation" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/ShareBasedCompensationNarrativeDetail" xlink:href="swx-20181231.xsd#ShareBasedCompensationNarrativeDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/ShareBasedCompensationScheduleOfNonvestedPerformanceAndRestrictedStockUnitPlansDetail" xlink:href="swx-20181231.xsd#ShareBasedCompensationScheduleOfNonvestedPerformanceAndRestrictedStockUnitPlansDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/ShareBasedCompensationScheduleOfShareBasedPlanCompensationExpenseIncludingCashAwardDetail" xlink:href="swx-20181231.xsd#ShareBasedCompensationScheduleOfShareBasedPlanCompensationExpenseIncludingCashAwardDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/ShareBasedCompensationScheduleOfStockOptionsActivityDetail" xlink:href="swx-20181231.xsd#ShareBasedCompensationScheduleOfStockOptionsActivityDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/ShareBasedCompensationSummaryOfMarketPricesOfCommonStockDetail" xlink:href="swx-20181231.xsd#ShareBasedCompensationSummaryOfMarketPricesOfCommonStockDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/ShareBasedCompensationTables" xlink:href="swx-20181231.xsd#ShareBasedCompensationTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/ShortTermDebt" xlink:href="swx-20181231.xsd#ShortTermDebt" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/ShortTermDebtDetail" xlink:href="swx-20181231.xsd#ShortTermDebtDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/UtilityInfrastructureServicesNoncontrollingInterests" xlink:href="swx-20181231.xsd#UtilityInfrastructureServicesNoncontrollingInterests" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/UtilityInfrastructureServicesNoncontrollingInterestsAdditionalInformationDetail" xlink:href="swx-20181231.xsd#UtilityInfrastructureServicesNoncontrollingInterestsAdditionalInformationDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/UtilityInfrastructureServicesNoncontrollingInterestsSummaryOfRedeemableNoncontrollingInterestDetail" xlink:href="swx-20181231.xsd#UtilityInfrastructureServicesNoncontrollingInterestsSummaryOfRedeemableNoncontrollingInterestDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/UtilityInfrastructureServicesNoncontrollingInterestsTables" xlink:href="swx-20181231.xsd#UtilityInfrastructureServicesNoncontrollingInterestsTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/UtilityPlantAndLeases" xlink:href="swx-20181231.xsd#UtilityPlantAndLeases" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/UtilityPlantAndLeasesNarrativeDetail" xlink:href="swx-20181231.xsd#UtilityPlantAndLeasesNarrativeDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/UtilityPlantAndLeasesScheduleOfDepreciationAndAmortizationExpenseDetail" xlink:href="swx-20181231.xsd#UtilityPlantAndLeasesScheduleOfDepreciationAndAmortizationExpenseDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/UtilityPlantAndLeasesScheduleOfFutureMinimumLeasePaymentsForOperatingLeasesDetail" xlink:href="swx-20181231.xsd#UtilityPlantAndLeasesScheduleOfFutureMinimumLeasePaymentsForOperatingLeasesDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/UtilityPlantAndLeasesScheduleOfNetUtilityPlantDetail" xlink:href="swx-20181231.xsd#UtilityPlantAndLeasesScheduleOfNetUtilityPlantDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/UtilityPlantAndLeasesScheduleOfRentalPaymentsForOperatingLeasesDetail" xlink:href="swx-20181231.xsd#UtilityPlantAndLeasesScheduleOfRentalPaymentsForOperatingLeasesDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.southwestgas.com/role/UtilityPlantAndLeasesTables" xlink:href="swx-20181231.xsd#UtilityPlantAndLeasesTables" xlink:type="simple" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/BackgroundOrganizationAndSummaryOfSignificantAccountingPolicies" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/BackgroundOrganizationAndSummaryOfSignificantAccountingPoliciesNarrativeDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/BackgroundOrganizationAndSummaryOfSignificantAccountingPoliciesOtherIncomeDeductionsDetail" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherNonoperatingIncomeExpense" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_41e96f8d-e499-8de8-69a8-27f1c7d4df6e" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LifeInsuranceCorporateOrBankOwnedChangeInValue" xlink:label="loc_us-gaap_LifeInsuranceCorporateOrBankOwnedChangeInValue_ac77efce-3f40-d301-508e-be268a607fae" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherNonoperatingIncomeExpense_41e96f8d-e499-8de8-69a8-27f1c7d4df6e" xlink:to="loc_us-gaap_LifeInsuranceCorporateOrBankOwnedChangeInValue_ac77efce-3f40-d301-508e-be268a607fae" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_InterestIncomeOther" xlink:label="loc_us-gaap_InterestIncomeOther_927f3a49-3cce-f44d-2750-b82061b05961" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherNonoperatingIncomeExpense_41e96f8d-e499-8de8-69a8-27f1c7d4df6e" xlink:to="loc_us-gaap_InterestIncomeOther_927f3a49-3cce-f44d-2750-b82061b05961" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquity" xlink:label="loc_us-gaap_PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquity_e6805b8d-c095-b84b-4b3a-84164080c52a" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherNonoperatingIncomeExpense_41e96f8d-e499-8de8-69a8-27f1c7d4df6e" xlink:to="loc_us-gaap_PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquity_e6805b8d-c095-b84b-4b3a-84164080c52a" xlink:type="arc" />
    <link:loc xlink:href="swx-20181231.xsd#swx_MiscellaneousIncomeExpense" xlink:label="loc_swx_MiscellaneousIncomeExpense_22d8d9b4-8410-e843-1ad9-0e712b86f644" xlink:type="locator" />
    <link:calculationArc order="4" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherNonoperatingIncomeExpense_41e96f8d-e499-8de8-69a8-27f1c7d4df6e" xlink:to="loc_swx_MiscellaneousIncomeExpense_22d8d9b4-8410-e843-1ad9-0e712b86f644" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DefinedBenefitPlanActuarialGainLossImmediateRecognitionAsComponentInNetPeriodicBenefitCostCredit" xlink:label="loc_us-gaap_DefinedBenefitPlanActuarialGainLossImmediateRecognitionAsComponentInNetPeriodicBenefitCostCredit_108a2aab-8e81-6380-c320-ac34cb661cd8" xlink:type="locator" />
    <link:calculationArc order="5" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherNonoperatingIncomeExpense_41e96f8d-e499-8de8-69a8-27f1c7d4df6e" xlink:to="loc_us-gaap_DefinedBenefitPlanActuarialGainLossImmediateRecognitionAsComponentInNetPeriodicBenefitCostCredit_108a2aab-8e81-6380-c320-ac34cb661cd8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ForeignCurrencyTransactionGainLossRealized" xlink:label="loc_us-gaap_ForeignCurrencyTransactionGainLossRealized_db31a483-6e91-bb9e-3d96-563ab3da2f2c" xlink:type="locator" />
    <link:calculationArc order="6" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherNonoperatingIncomeExpense_41e96f8d-e499-8de8-69a8-27f1c7d4df6e" xlink:to="loc_us-gaap_ForeignCurrencyTransactionGainLossRealized_db31a483-6e91-bb9e-3d96-563ab3da2f2c" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeLossFromEquityMethodInvestments" xlink:label="loc_us-gaap_IncomeLossFromEquityMethodInvestments_d01a4d5f-b660-27b4-db84-9a80227862fc" xlink:type="locator" />
    <link:calculationArc order="7" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherNonoperatingIncomeExpense_41e96f8d-e499-8de8-69a8-27f1c7d4df6e" xlink:to="loc_us-gaap_IncomeLossFromEquityMethodInvestments_d01a4d5f-b660-27b4-db84-9a80227862fc" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/BackgroundOrganizationAndSummaryOfSignificantAccountingPoliciesPolicies" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/BackgroundOrganizationAndSummaryOfSignificantAccountingPoliciesScheduleOfCapitalizedAndDebtPortionOfAfudcDetail" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PublicUtilitiesAllowanceForFundsUsedDuringConstructionAdditions" xlink:label="loc_us-gaap_PublicUtilitiesAllowanceForFundsUsedDuringConstructionAdditions_6b574293-f1c9-cfe2-ed04-114edd43b629" xlink:type="locator" />
    <link:loc xlink:href="swx-20181231.xsd#swx_PublicUtilitiesAllowanceforFundsUsedDuringConstructionCapitalizedDebtPortion" xlink:label="loc_swx_PublicUtilitiesAllowanceforFundsUsedDuringConstructionCapitalizedDebtPortion_808293372ACC598527FD0DD119071EC5" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_PublicUtilitiesAllowanceForFundsUsedDuringConstructionAdditions_6b574293-f1c9-cfe2-ed04-114edd43b629" xlink:to="loc_swx_PublicUtilitiesAllowanceforFundsUsedDuringConstructionCapitalizedDebtPortion_808293372ACC598527FD0DD119071EC5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquity" xlink:label="loc_us-gaap_PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquity_e6805b8d-c095-b84b-4b3a-84164080c52a" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_PublicUtilitiesAllowanceForFundsUsedDuringConstructionAdditions_6b574293-f1c9-cfe2-ed04-114edd43b629" xlink:to="loc_us-gaap_PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquity_e6805b8d-c095-b84b-4b3a-84164080c52a" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/BackgroundOrganizationAndSummaryOfSignificantAccountingPoliciesScheduleOfEarningsPerShareBasicAndDilutedDetail" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_21ce4f2f-397c-6c02-8635-7c94146a06a0" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_2dd9a981-e559-d141-f1c2-4db79f71a7ef" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_21ce4f2f-397c-6c02-8635-7c94146a06a0" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_2dd9a981-e559-d141-f1c2-4db79f71a7ef" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncrementalCommonSharesAttributableToCallOptionsAndWarrants" xlink:label="loc_us-gaap_IncrementalCommonSharesAttributableToCallOptionsAndWarrants_803ef030-81c3-f313-0d68-8fbe2e1bdf1b" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_21ce4f2f-397c-6c02-8635-7c94146a06a0" xlink:to="loc_us-gaap_IncrementalCommonSharesAttributableToCallOptionsAndWarrants_803ef030-81c3-f313-0d68-8fbe2e1bdf1b" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncrementalCommonSharesAttributableToEquityForwardAgreements" xlink:label="loc_us-gaap_IncrementalCommonSharesAttributableToEquityForwardAgreements_51ad23aa-10ab-a3e4-4dc1-873e35a15604" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_21ce4f2f-397c-6c02-8635-7c94146a06a0" xlink:to="loc_us-gaap_IncrementalCommonSharesAttributableToEquityForwardAgreements_51ad23aa-10ab-a3e4-4dc1-873e35a15604" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncrementalCommonSharesAttributableToNonvestedSharesWithForfeitableDividends" xlink:label="loc_us-gaap_IncrementalCommonSharesAttributableToNonvestedSharesWithForfeitableDividends_66bbb7f4-5728-20f8-d291-a9b5e10a2fb2" xlink:type="locator" />
    <link:calculationArc order="4" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_21ce4f2f-397c-6c02-8635-7c94146a06a0" xlink:to="loc_us-gaap_IncrementalCommonSharesAttributableToNonvestedSharesWithForfeitableDividends_66bbb7f4-5728-20f8-d291-a9b5e10a2fb2" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/BackgroundOrganizationAndSummaryOfSignificantAccountingPoliciesScheduleOfEstimatedFutureAmortizationOfIntangibleAssetsDetail" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsNet" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_d3bdc20c-5c58-6be6-d756-0ace6a97f212" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths_423e6bba-f43d-931c-5711-51d5522b2aaa" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsNet_d3bdc20c-5c58-6be6-d756-0ace6a97f212" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths_423e6bba-f43d-931c-5711-51d5522b2aaa" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo_28c91f3b-370e-e76f-4199-69e4166aabc6" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsNet_d3bdc20c-5c58-6be6-d756-0ace6a97f212" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo_28c91f3b-370e-e76f-4199-69e4166aabc6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree_f7796428-4176-97fe-5145-79a026d8547a" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsNet_d3bdc20c-5c58-6be6-d756-0ace6a97f212" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree_f7796428-4176-97fe-5145-79a026d8547a" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour_71fd8e03-8eaf-f20c-786b-5e0492fb281b" xlink:type="locator" />
    <link:calculationArc order="4" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsNet_d3bdc20c-5c58-6be6-d756-0ace6a97f212" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour_71fd8e03-8eaf-f20c-786b-5e0492fb281b" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFive" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFive_8d652bfd-fc92-51b1-30d6-b90c4a94f960" xlink:type="locator" />
    <link:calculationArc order="5" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsNet_d3bdc20c-5c58-6be6-d756-0ace6a97f212" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFive_8d652bfd-fc92-51b1-30d6-b90c4a94f960" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseAfterYearFive" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseAfterYearFive_0e7343bd-e798-afc0-7fcc-ed296ae9f91c" xlink:type="locator" />
    <link:calculationArc order="6" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsNet_d3bdc20c-5c58-6be6-d756-0ace6a97f212" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseAfterYearFive_0e7343bd-e798-afc0-7fcc-ed296ae9f91c" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/BackgroundOrganizationAndSummaryOfSignificantAccountingPoliciesScheduleOfGoodwillDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/BackgroundOrganizationAndSummaryOfSignificantAccountingPoliciesScheduleOfOtherPropertyAndInvestmentsDetail" xlink:type="extended">
    <link:loc xlink:href="swx-20181231.xsd#swx_OtherPropertyAndInvestments" xlink:label="loc_swx_OtherPropertyAndInvestments_7b3c29e6-282e-196d-e634-0e712b8a4292" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CashSurrenderValueOfLifeInsurance" xlink:label="loc_us-gaap_CashSurrenderValueOfLifeInsurance_ee92502f-7c41-bf37-7fee-a2a3105530e9" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_swx_OtherPropertyAndInvestments_7b3c29e6-282e-196d-e634-0e712b8a4292" xlink:to="loc_us-gaap_CashSurrenderValueOfLifeInsurance_ee92502f-7c41-bf37-7fee-a2a3105530e9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PropertyPlantAndEquipmentOtherNet" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentOtherNet_c41a8a80-f055-9582-ccd3-a3e2c4d7a3b0" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_swx_OtherPropertyAndInvestments_7b3c29e6-282e-196d-e634-0e712b8a4292" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentOtherNet_c41a8a80-f055-9582-ccd3-a3e2c4d7a3b0" xlink:type="arc" />
    <link:loc xlink:href="swx-20181231.xsd#swx_PropertyPlantEquipmentAndIntangibleAssetsGross" xlink:label="loc_swx_PropertyPlantEquipmentAndIntangibleAssetsGross_7085ec2c-b16c-0d38-9bac-0e712b879535" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_swx_OtherPropertyAndInvestments_7b3c29e6-282e-196d-e634-0e712b8a4292" xlink:to="loc_swx_PropertyPlantEquipmentAndIntangibleAssetsGross_7085ec2c-b16c-0d38-9bac-0e712b879535" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_0a08cda9-11b3-e7ac-3fc9-3a23c67d9b96" xlink:type="locator" />
    <link:calculationArc order="4" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_swx_OtherPropertyAndInvestments_7b3c29e6-282e-196d-e634-0e712b8a4292" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_0a08cda9-11b3-e7ac-3fc9-3a23c67d9b96" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/BackgroundOrganizationAndSummaryOfSignificantAccountingPoliciesSummaryOfIntangibleAssetsDetail" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsNet" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_d3bdc20c-5c58-6be6-d756-0ace6a97f212" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsGross" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_7a49df76-38f6-6baa-87dd-2e9a7efd8303" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsNet_d3bdc20c-5c58-6be6-d756-0ace6a97f212" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_7a49df76-38f6-6baa-87dd-2e9a7efd8303" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_c9279b6a-f262-f140-7696-5ec40778343f" xlink:type="locator" />
    <link:calculationArc order="2" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsNet_d3bdc20c-5c58-6be6-d756-0ace6a97f212" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_c9279b6a-f262-f140-7696-5ec40778343f" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/BackgroundOrganizationAndSummaryOfSignificantAccountingPoliciesTables" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/BusinessAcquisitions" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/BusinessAcquisitionsNarrativeDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/BusinessAcquisitionsScheduleOfProFormaConsolidatedFinancialInformationDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/BusinessAcquisitionsScheduleOfStatementsOfIncomeOperationsDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/BusinessAcquisitionsSummaryOfFairValuesOfAssetsAcquiredAndLiabilitiesAssumedDetail" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_a49f91fe-6036-ab86-6a1a-6ac66f348274" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets_2fb474b5-5859-9678-205e-8aa88ca40daa" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_a49f91fe-6036-ab86-6a1a-6ac66f348274" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets_2fb474b5-5859-9678-205e-8aa88ca40daa" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_395f9bb0-2492-f247-ce6b-39e67453292c" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets_2fb474b5-5859-9678-205e-8aa88ca40daa" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_395f9bb0-2492-f247-ce6b-39e67453292c" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables_8ce68675-8129-3ab4-cbd9-33127f150e28" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets_2fb474b5-5859-9678-205e-8aa88ca40daa" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables_8ce68675-8129-3ab4-cbd9-33127f150e28" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_090d08a1-b8fd-3634-47b8-7dcb68699de1" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets_2fb474b5-5859-9678-205e-8aa88ca40daa" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_090d08a1-b8fd-3634-47b8-7dcb68699de1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsPrepaidExpenseAndOtherAssets" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsPrepaidExpenseAndOtherAssets_4969e367-c531-0df1-f44b-bfbc106efa7e" xlink:type="locator" />
    <link:calculationArc order="4" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets_2fb474b5-5859-9678-205e-8aa88ca40daa" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsPrepaidExpenseAndOtherAssets_4969e367-c531-0df1-f44b-bfbc106efa7e" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill_588b212f-0609-2b89-932f-cbe7e57377ff" xlink:type="locator" />
    <link:calculationArc order="5" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets_2fb474b5-5859-9678-205e-8aa88ca40daa" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill_588b212f-0609-2b89-932f-cbe7e57377ff" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_Goodwill" xlink:label="loc_us-gaap_Goodwill_831ad0b9-9dba-3997-20e6-e99a19aa28db" xlink:type="locator" />
    <link:calculationArc order="6" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets_2fb474b5-5859-9678-205e-8aa88ca40daa" xlink:to="loc_us-gaap_Goodwill_831ad0b9-9dba-3997-20e6-e99a19aa28db" xlink:type="arc" />
    <link:loc xlink:href="swx-20181231.xsd#swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedOtherReceivables" xlink:label="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedOtherReceivables_4230C2BEDFFF219117230C4428DAD128" xlink:type="locator" />
    <link:calculationArc order="7" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets_2fb474b5-5859-9678-205e-8aa88ca40daa" xlink:to="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedOtherReceivables_4230C2BEDFFF219117230C4428DAD128" xlink:type="arc" />
    <link:loc xlink:href="swx-20181231.xsd#swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOtherReceivables" xlink:label="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOtherReceivables_fa87e9f2-0c13-c4ea-ac75-580e3916b651" xlink:type="locator" />
    <link:calculationArc order="8" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets_2fb474b5-5859-9678-205e-8aa88ca40daa" xlink:to="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOtherReceivables_fa87e9f2-0c13-c4ea-ac75-580e3916b651" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilities" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilities_c8504d26-e8a8-f6de-fac9-47ac4ee2abaf" xlink:type="locator" />
    <link:calculationArc order="2" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_a49f91fe-6036-ab86-6a1a-6ac66f348274" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilities_c8504d26-e8a8-f6de-fac9-47ac4ee2abaf" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilities" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilities_c1d14e08-6047-bdc6-cd0b-14a44c47d9d6" xlink:type="locator" />
    <link:calculationArc order="3" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_a49f91fe-6036-ab86-6a1a-6ac66f348274" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilities_c1d14e08-6047-bdc6-cd0b-14a44c47d9d6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_cc1d8741-0bf1-0f1b-dbad-6859add56d00" xlink:type="locator" />
    <link:calculationArc order="4" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_a49f91fe-6036-ab86-6a1a-6ac66f348274" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_cc1d8741-0bf1-0f1b-dbad-6859add56d00" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable_fbe331bf-e36a-7435-2eec-e3249b6c0997" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_cc1d8741-0bf1-0f1b-dbad-6859add56d00" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable_fbe331bf-e36a-7435-2eec-e3249b6c0997" xlink:type="arc" />
    <link:loc xlink:href="swx-20181231.xsd#swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedAccruedLiabilities" xlink:label="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedAccruedLiabilities_481BF3EB08161609A47A0C40219D847E" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_cc1d8741-0bf1-0f1b-dbad-6859add56d00" xlink:to="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedAccruedLiabilities_481BF3EB08161609A47A0C40219D847E" xlink:type="arc" />
    <link:loc xlink:href="swx-20181231.xsd#swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedDeferredCompensationAndRelatedAccruedTaxes" xlink:label="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedDeferredCompensationAndRelatedAccruedTaxes_41D6B33AC53711FF19A00C48E6B07AE5" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_cc1d8741-0bf1-0f1b-dbad-6859add56d00" xlink:to="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedDeferredCompensationAndRelatedAccruedTaxes_41D6B33AC53711FF19A00C48E6B07AE5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther_403bd7bd-aec1-42d0-9dba-3894488c17e9" xlink:type="locator" />
    <link:calculationArc order="4" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_cc1d8741-0bf1-0f1b-dbad-6859add56d00" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther_403bd7bd-aec1-42d0-9dba-3894488c17e9" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/BusinessAcquisitionsSummaryOfFairValuesOfAssetsAcquiredAndLiabilitiesAssumedDetailCalc2" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/BusinessAcquisitionsTables" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/CommitmentsAndContingencies" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/CommitmentsAndContingenciesDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/CommonStock" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/CommonStockDetail" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ProceedsFromIssuanceOfCommonStock" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfCommonStock_6ec8bc8e-bcd9-36ad-d8ae-2c2fa1dfd920" xlink:type="locator" />
    <link:loc xlink:href="swx-20181231.xsd#swx_ProceedsFromIssuanceOfCommonStockGross" xlink:label="loc_swx_ProceedsFromIssuanceOfCommonStockGross_1F087CD1C7234F28D1BBA520D19F2983" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_ProceedsFromIssuanceOfCommonStock_6ec8bc8e-bcd9-36ad-d8ae-2c2fa1dfd920" xlink:to="loc_swx_ProceedsFromIssuanceOfCommonStockGross_1F087CD1C7234F28D1BBA520D19F2983" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PaymentsOfStockIssuanceCosts" xlink:label="loc_us-gaap_PaymentsOfStockIssuanceCosts_ea422513-12bd-029b-0166-7c34286633bc" xlink:type="locator" />
    <link:calculationArc order="2" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_ProceedsFromIssuanceOfCommonStock_6ec8bc8e-bcd9-36ad-d8ae-2c2fa1dfd920" xlink:to="loc_us-gaap_PaymentsOfStockIssuanceCosts_ea422513-12bd-029b-0166-7c34286633bc" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/CommonStockTables" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/ConsolidatedBalanceSheets" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_Assets" xlink:label="loc_us-gaap_Assets_96dd7052-744e-d270-4e77-67944ec39152" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PublicUtilitiesPropertyPlantAndEquipmentNet" xlink:label="loc_us-gaap_PublicUtilitiesPropertyPlantAndEquipmentNet_73987971-d446-86f2-6a5f-eb1fe277f208" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_96dd7052-744e-d270-4e77-67944ec39152" xlink:to="loc_us-gaap_PublicUtilitiesPropertyPlantAndEquipmentNet_73987971-d446-86f2-6a5f-eb1fe277f208" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PublicUtilitiesPropertyPlantAndEquipmentPlantInService" xlink:label="loc_us-gaap_PublicUtilitiesPropertyPlantAndEquipmentPlantInService_402d614f-d54b-9f1d-d560-88bcc4adbbbc" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_PublicUtilitiesPropertyPlantAndEquipmentNet_73987971-d446-86f2-6a5f-eb1fe277f208" xlink:to="loc_us-gaap_PublicUtilitiesPropertyPlantAndEquipmentPlantInService_402d614f-d54b-9f1d-d560-88bcc4adbbbc" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PublicUtilitiesPropertyPlantAndEquipmentAccumulatedDepreciation" xlink:label="loc_us-gaap_PublicUtilitiesPropertyPlantAndEquipmentAccumulatedDepreciation_daba4c89-1574-43ad-2cdb-6a349ae724c3" xlink:type="locator" />
    <link:calculationArc order="2" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_PublicUtilitiesPropertyPlantAndEquipmentNet_73987971-d446-86f2-6a5f-eb1fe277f208" xlink:to="loc_us-gaap_PublicUtilitiesPropertyPlantAndEquipmentAccumulatedDepreciation_daba4c89-1574-43ad-2cdb-6a349ae724c3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PublicUtilitiesPropertyPlantAndEquipmentConstructionWorkInProgress" xlink:label="loc_us-gaap_PublicUtilitiesPropertyPlantAndEquipmentConstructionWorkInProgress_48a13d8b-0c3b-31fc-c3a7-b1a4b5397d4b" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_PublicUtilitiesPropertyPlantAndEquipmentNet_73987971-d446-86f2-6a5f-eb1fe277f208" xlink:to="loc_us-gaap_PublicUtilitiesPropertyPlantAndEquipmentConstructionWorkInProgress_48a13d8b-0c3b-31fc-c3a7-b1a4b5397d4b" xlink:type="arc" />
    <link:loc xlink:href="swx-20181231.xsd#swx_OtherPropertyAndInvestments" xlink:label="loc_swx_OtherPropertyAndInvestments_7b3c29e6-282e-196d-e634-0e712b8a4292" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_96dd7052-744e-d270-4e77-67944ec39152" xlink:to="loc_swx_OtherPropertyAndInvestments_7b3c29e6-282e-196d-e634-0e712b8a4292" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AssetsCurrent" xlink:label="loc_us-gaap_AssetsCurrent_d79dcc1c-93de-0ecd-2bd5-7c1f224c9b98" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_96dd7052-744e-d270-4e77-67944ec39152" xlink:to="loc_us-gaap_AssetsCurrent_d79dcc1c-93de-0ecd-2bd5-7c1f224c9b98" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_32f41ea9-05c6-e713-464b-586a571d1c1f" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_d79dcc1c-93de-0ecd-2bd5-7c1f224c9b98" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_32f41ea9-05c6-e713-464b-586a571d1c1f" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AccountsReceivableNetCurrent" xlink:label="loc_us-gaap_AccountsReceivableNetCurrent_928a1618-af56-709a-989c-a303706b8ca2" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_d79dcc1c-93de-0ecd-2bd5-7c1f224c9b98" xlink:to="loc_us-gaap_AccountsReceivableNetCurrent_928a1618-af56-709a-989c-a303706b8ca2" xlink:type="arc" />
    <link:loc xlink:href="swx-20181231.xsd#swx_AccruedUtilityRevenue" xlink:label="loc_swx_AccruedUtilityRevenue_032cdf06-9985-a41d-203b-0e712b88e52a" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_d79dcc1c-93de-0ecd-2bd5-7c1f224c9b98" xlink:to="loc_swx_AccruedUtilityRevenue_032cdf06-9985-a41d-203b-0e712b88e52a" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeTaxesReceivable" xlink:label="loc_us-gaap_IncomeTaxesReceivable_ebb94f1a-1386-5eed-9402-f0f0e2cd300b" xlink:type="locator" />
    <link:calculationArc order="4" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_d79dcc1c-93de-0ecd-2bd5-7c1f224c9b98" xlink:to="loc_us-gaap_IncomeTaxesReceivable_ebb94f1a-1386-5eed-9402-f0f0e2cd300b" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredGasCost" xlink:label="loc_us-gaap_DeferredGasCost_e87da4ca-3c89-6677-3b3f-440e51de6903" xlink:type="locator" />
    <link:calculationArc order="5" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_d79dcc1c-93de-0ecd-2bd5-7c1f224c9b98" xlink:to="loc_us-gaap_DeferredGasCost_e87da4ca-3c89-6677-3b3f-440e51de6903" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PrepaidExpenseAndOtherAssetsCurrent" xlink:label="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_ce9014ac-0ac4-6ed2-b53f-a0edc046d6b4" xlink:type="locator" />
    <link:calculationArc order="6" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_d79dcc1c-93de-0ecd-2bd5-7c1f224c9b98" xlink:to="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_ce9014ac-0ac4-6ed2-b53f-a0edc046d6b4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AssetsNoncurrentOtherThanNoncurrentInvestmentsAndPropertyPlantAndEquipment" xlink:label="loc_us-gaap_AssetsNoncurrentOtherThanNoncurrentInvestmentsAndPropertyPlantAndEquipment_0e21e89d-212b-ade3-2cba-e768d4a9f9c5" xlink:type="locator" />
    <link:calculationArc order="4" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_96dd7052-744e-d270-4e77-67944ec39152" xlink:to="loc_us-gaap_AssetsNoncurrentOtherThanNoncurrentInvestmentsAndPropertyPlantAndEquipment_0e21e89d-212b-ade3-2cba-e768d4a9f9c5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_Goodwill" xlink:label="loc_us-gaap_Goodwill_831ad0b9-9dba-3997-20e6-e99a19aa28db" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsNoncurrentOtherThanNoncurrentInvestmentsAndPropertyPlantAndEquipment_0e21e89d-212b-ade3-2cba-e768d4a9f9c5" xlink:to="loc_us-gaap_Goodwill_831ad0b9-9dba-3997-20e6-e99a19aa28db" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredIncomeTaxAssetsNet" xlink:label="loc_us-gaap_DeferredIncomeTaxAssetsNet_6544a746-9524-1b61-e235-04d48d39f116" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsNoncurrentOtherThanNoncurrentInvestmentsAndPropertyPlantAndEquipment_0e21e89d-212b-ade3-2cba-e768d4a9f9c5" xlink:to="loc_us-gaap_DeferredIncomeTaxAssetsNet_6544a746-9524-1b61-e235-04d48d39f116" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherAssetsNoncurrent" xlink:label="loc_us-gaap_OtherAssetsNoncurrent_ddb0d184-2205-2a10-5b0e-faf2ccd717ae" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsNoncurrentOtherThanNoncurrentInvestmentsAndPropertyPlantAndEquipment_0e21e89d-212b-ade3-2cba-e768d4a9f9c5" xlink:to="loc_us-gaap_OtherAssetsNoncurrent_ddb0d184-2205-2a10-5b0e-faf2ccd717ae" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquity" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_63817d40-f759-fa9c-45a5-8bbbb36ed5c9" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CapitalizationLongtermDebtAndEquity" xlink:label="loc_us-gaap_CapitalizationLongtermDebtAndEquity_04d293e9-9fa0-30e1-ddd5-a361b8a38e03" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquity_63817d40-f759-fa9c-45a5-8bbbb36ed5c9" xlink:to="loc_us-gaap_CapitalizationLongtermDebtAndEquity_04d293e9-9fa0-30e1-ddd5-a361b8a38e03" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_e0c0480e-e6f5-c4df-ce25-1ffa4a8c827a" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CapitalizationLongtermDebtAndEquity_04d293e9-9fa0-30e1-ddd5-a361b8a38e03" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_e0c0480e-e6f5-c4df-ce25-1ffa4a8c827a" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StockholdersEquity" xlink:label="loc_us-gaap_StockholdersEquity_6765f135-8c69-bebc-a116-d59a52a5b2f2" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_e0c0480e-e6f5-c4df-ce25-1ffa4a8c827a" xlink:to="loc_us-gaap_StockholdersEquity_6765f135-8c69-bebc-a116-d59a52a5b2f2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CommonStockValue" xlink:label="loc_us-gaap_CommonStockValue_aefe3f0c-abe4-5b83-9a64-da77d8e253dd" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_6765f135-8c69-bebc-a116-d59a52a5b2f2" xlink:to="loc_us-gaap_CommonStockValue_aefe3f0c-abe4-5b83-9a64-da77d8e253dd" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AdditionalPaidInCapitalCommonStock" xlink:label="loc_us-gaap_AdditionalPaidInCapitalCommonStock_df284507-8ac7-eed1-41db-05e81b70be6d" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_6765f135-8c69-bebc-a116-d59a52a5b2f2" xlink:to="loc_us-gaap_AdditionalPaidInCapitalCommonStock_df284507-8ac7-eed1-41db-05e81b70be6d" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_798442bf-12e1-d944-3fa1-8b797b67482e" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_6765f135-8c69-bebc-a116-d59a52a5b2f2" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_798442bf-12e1-d944-3fa1-8b797b67482e" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RetainedEarningsAccumulatedDeficit" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_a59bc5ae-63a0-c9bc-32f7-e2bd9f32bd26" xlink:type="locator" />
    <link:calculationArc order="4" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_6765f135-8c69-bebc-a116-d59a52a5b2f2" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_a59bc5ae-63a0-c9bc-32f7-e2bd9f32bd26" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_MinorityInterest" xlink:label="loc_us-gaap_MinorityInterest_a9feabf5-0bf0-3efe-740e-f5e41a4b3194" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_e0c0480e-e6f5-c4df-ce25-1ffa4a8c827a" xlink:to="loc_us-gaap_MinorityInterest_a9feabf5-0bf0-3efe-740e-f5e41a4b3194" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RedeemableNoncontrollingInterestEquityCarryingAmount" xlink:label="loc_us-gaap_RedeemableNoncontrollingInterestEquityCarryingAmount_8c6cb868-c2c5-f73a-a7f6-65b98067e41e" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CapitalizationLongtermDebtAndEquity_04d293e9-9fa0-30e1-ddd5-a361b8a38e03" xlink:to="loc_us-gaap_RedeemableNoncontrollingInterestEquityCarryingAmount_8c6cb868-c2c5-f73a-a7f6-65b98067e41e" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LongTermDebtNoncurrent" xlink:label="loc_us-gaap_LongTermDebtNoncurrent_fcfc6b17-bfc5-2ebc-3fc1-751aa446a572" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CapitalizationLongtermDebtAndEquity_04d293e9-9fa0-30e1-ddd5-a361b8a38e03" xlink:to="loc_us-gaap_LongTermDebtNoncurrent_fcfc6b17-bfc5-2ebc-3fc1-751aa446a572" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LiabilitiesCurrent" xlink:label="loc_us-gaap_LiabilitiesCurrent_2dcbbde2-9146-a0ba-7f6c-c71b481e0841" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquity_63817d40-f759-fa9c-45a5-8bbbb36ed5c9" xlink:to="loc_us-gaap_LiabilitiesCurrent_2dcbbde2-9146-a0ba-7f6c-c71b481e0841" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LongTermDebtCurrent" xlink:label="loc_us-gaap_LongTermDebtCurrent_0d8925ae-714a-26e4-aa69-2d9eac65a5c6" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_2dcbbde2-9146-a0ba-7f6c-c71b481e0841" xlink:to="loc_us-gaap_LongTermDebtCurrent_0d8925ae-714a-26e4-aa69-2d9eac65a5c6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShortTermBorrowings" xlink:label="loc_us-gaap_ShortTermBorrowings_422d7c41-753d-7765-5880-50978d071d31" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_2dcbbde2-9146-a0ba-7f6c-c71b481e0841" xlink:to="loc_us-gaap_ShortTermBorrowings_422d7c41-753d-7765-5880-50978d071d31" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AccountsPayableCurrent" xlink:label="loc_us-gaap_AccountsPayableCurrent_c2c48170-d0ff-2c37-effc-ff5f53e30dcb" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_2dcbbde2-9146-a0ba-7f6c-c71b481e0841" xlink:to="loc_us-gaap_AccountsPayableCurrent_c2c48170-d0ff-2c37-effc-ff5f53e30dcb" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CustomerDepositsCurrent" xlink:label="loc_us-gaap_CustomerDepositsCurrent_525eaaa4-1e5a-7288-6b91-5882a9305b35" xlink:type="locator" />
    <link:calculationArc order="4" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_2dcbbde2-9146-a0ba-7f6c-c71b481e0841" xlink:to="loc_us-gaap_CustomerDepositsCurrent_525eaaa4-1e5a-7288-6b91-5882a9305b35" xlink:type="arc" />
    <link:loc xlink:href="swx-20181231.xsd#swx_IncomeTaxesPayableNet" xlink:label="loc_swx_IncomeTaxesPayableNet_61e9e0cd-aa9e-812e-8a58-0e712b8cfb33" xlink:type="locator" />
    <link:calculationArc order="5" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_2dcbbde2-9146-a0ba-7f6c-c71b481e0841" xlink:to="loc_swx_IncomeTaxesPayableNet_61e9e0cd-aa9e-812e-8a58-0e712b8cfb33" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AccrualForTaxesOtherThanIncomeTaxesCurrent" xlink:label="loc_us-gaap_AccrualForTaxesOtherThanIncomeTaxesCurrent_d31892de-11c1-2896-c1b4-6e61bb9452f8" xlink:type="locator" />
    <link:calculationArc order="6" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_2dcbbde2-9146-a0ba-7f6c-c71b481e0841" xlink:to="loc_us-gaap_AccrualForTaxesOtherThanIncomeTaxesCurrent_d31892de-11c1-2896-c1b4-6e61bb9452f8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_InterestPayableCurrent" xlink:label="loc_us-gaap_InterestPayableCurrent_84c97d53-d75c-0fec-d05e-498cb2460450" xlink:type="locator" />
    <link:calculationArc order="7" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_2dcbbde2-9146-a0ba-7f6c-c71b481e0841" xlink:to="loc_us-gaap_InterestPayableCurrent_84c97d53-d75c-0fec-d05e-498cb2460450" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredGasPurchasesCurrent" xlink:label="loc_us-gaap_DeferredGasPurchasesCurrent_8764c553-38fa-c028-af35-83f677de7a66" xlink:type="locator" />
    <link:calculationArc order="8" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_2dcbbde2-9146-a0ba-7f6c-c71b481e0841" xlink:to="loc_us-gaap_DeferredGasPurchasesCurrent_8764c553-38fa-c028-af35-83f677de7a66" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DueToAffiliateCurrent" xlink:label="loc_us-gaap_DueToAffiliateCurrent_1c0eed85-52b7-ef32-30fb-b4a366c9b460" xlink:type="locator" />
    <link:calculationArc order="9" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_2dcbbde2-9146-a0ba-7f6c-c71b481e0841" xlink:to="loc_us-gaap_DueToAffiliateCurrent_1c0eed85-52b7-ef32-30fb-b4a366c9b460" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherLiabilitiesCurrent" xlink:label="loc_us-gaap_OtherLiabilitiesCurrent_4bcdb937-432e-7a7e-23c2-a441d7b89da5" xlink:type="locator" />
    <link:calculationArc order="10" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_2dcbbde2-9146-a0ba-7f6c-c71b481e0841" xlink:to="loc_us-gaap_OtherLiabilitiesCurrent_4bcdb937-432e-7a7e-23c2-a441d7b89da5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherLiabilitiesNoncurrent" xlink:label="loc_us-gaap_OtherLiabilitiesNoncurrent_bba08e5f-78e8-6c25-01a4-6720051135cc" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquity_63817d40-f759-fa9c-45a5-8bbbb36ed5c9" xlink:to="loc_us-gaap_OtherLiabilitiesNoncurrent_bba08e5f-78e8-6c25-01a4-6720051135cc" xlink:type="arc" />
    <link:loc xlink:href="swx-20181231.xsd#swx_DeferredIncomeTaxesAndUnamortizedInvestmentTaxCredits" xlink:label="loc_swx_DeferredIncomeTaxesAndUnamortizedInvestmentTaxCredits_ce9d3774-c632-dfd6-70da-0e712b79c434" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherLiabilitiesNoncurrent_bba08e5f-78e8-6c25-01a4-6720051135cc" xlink:to="loc_swx_DeferredIncomeTaxesAndUnamortizedInvestmentTaxCredits_ce9d3774-c632-dfd6-70da-0e712b79c434" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherAccruedLiabilitiesNoncurrent" xlink:label="loc_us-gaap_OtherAccruedLiabilitiesNoncurrent_278c7367-7f7a-9e5b-9c31-1041c7d59096" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherLiabilitiesNoncurrent_bba08e5f-78e8-6c25-01a4-6720051135cc" xlink:to="loc_us-gaap_OtherAccruedLiabilitiesNoncurrent_278c7367-7f7a-9e5b-9c31-1041c7d59096" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredCreditsAndOtherLiabilitiesNoncurrent" xlink:label="loc_us-gaap_DeferredCreditsAndOtherLiabilitiesNoncurrent_3d536018-86b9-0ada-c83e-dcbe5731aafb" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherLiabilitiesNoncurrent_bba08e5f-78e8-6c25-01a4-6720051135cc" xlink:to="loc_us-gaap_DeferredCreditsAndOtherLiabilitiesNoncurrent_3d536018-86b9-0ada-c83e-dcbe5731aafb" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/ConsolidatedBalanceSheetsParenthetical" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/ConsolidatedStatementsOfCashFlows" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations_fd33978d-50b8-db74-6695-8c6dbaac3547" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest_98ad2198-806f-6053-5326-b79be5cbb9ef" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations_fd33978d-50b8-db74-6695-8c6dbaac3547" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest_98ad2198-806f-6053-5326-b79be5cbb9ef" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DepreciationAndAmortization" xlink:label="loc_us-gaap_DepreciationAndAmortization_97b88949-d4fc-dff4-be7f-d39018557f4e" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations_fd33978d-50b8-db74-6695-8c6dbaac3547" xlink:to="loc_us-gaap_DepreciationAndAmortization_97b88949-d4fc-dff4-be7f-d39018557f4e" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncreaseDecreaseInDeferredIncomeTaxes" xlink:label="loc_us-gaap_IncreaseDecreaseInDeferredIncomeTaxes_852a0148-80e8-01e7-45e2-04986579e466" xlink:type="locator" />
    <link:calculationArc order="3" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations_fd33978d-50b8-db74-6695-8c6dbaac3547" xlink:to="loc_us-gaap_IncreaseDecreaseInDeferredIncomeTaxes_852a0148-80e8-01e7-45e2-04986579e466" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncreaseDecreaseInAccountsReceivable" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_5f96c19e-85fe-99f6-cec0-c2c9d7470ed4" xlink:type="locator" />
    <link:calculationArc order="4" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations_fd33978d-50b8-db74-6695-8c6dbaac3547" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_5f96c19e-85fe-99f6-cec0-c2c9d7470ed4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncreaseDecreaseInUnbilledReceivables" xlink:label="loc_us-gaap_IncreaseDecreaseInUnbilledReceivables_41adfb2c-6577-a630-96b7-f1964f7d3890" xlink:type="locator" />
    <link:calculationArc order="5" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations_fd33978d-50b8-db74-6695-8c6dbaac3547" xlink:to="loc_us-gaap_IncreaseDecreaseInUnbilledReceivables_41adfb2c-6577-a630-96b7-f1964f7d3890" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncreaseDecreaseInDeferredGasCost" xlink:label="loc_us-gaap_IncreaseDecreaseInDeferredGasCost_a79f3c72-fa61-8e2b-9bcb-436c1f546e77" xlink:type="locator" />
    <link:calculationArc order="6" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations_fd33978d-50b8-db74-6695-8c6dbaac3547" xlink:to="loc_us-gaap_IncreaseDecreaseInDeferredGasCost_a79f3c72-fa61-8e2b-9bcb-436c1f546e77" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncreaseDecreaseInAccountsPayable" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsPayable_0a39d2ee-656d-ead5-a676-41794b4da8f4" xlink:type="locator" />
    <link:calculationArc order="7" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations_fd33978d-50b8-db74-6695-8c6dbaac3547" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsPayable_0a39d2ee-656d-ead5-a676-41794b4da8f4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncreaseDecreaseInAccruedTaxesPayable" xlink:label="loc_us-gaap_IncreaseDecreaseInAccruedTaxesPayable_7b3c76f4-f4f7-d8c9-23c6-b259dabda37e" xlink:type="locator" />
    <link:calculationArc order="8" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations_fd33978d-50b8-db74-6695-8c6dbaac3547" xlink:to="loc_us-gaap_IncreaseDecreaseInAccruedTaxesPayable_7b3c76f4-f4f7-d8c9-23c6-b259dabda37e" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncreaseDecreaseInOtherCurrentAssetsAndLiabilitiesNet" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherCurrentAssetsAndLiabilitiesNet_27004e54-27fb-868f-b1d8-f8874a01e9b6" xlink:type="locator" />
    <link:calculationArc order="9" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations_fd33978d-50b8-db74-6695-8c6dbaac3547" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherCurrentAssetsAndLiabilitiesNet_27004e54-27fb-868f-b1d8-f8874a01e9b6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensation" xlink:label="loc_us-gaap_ShareBasedCompensation_90cbc3ab-f555-6407-b3b4-b2bfa84c9f18" xlink:type="locator" />
    <link:calculationArc order="10" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations_fd33978d-50b8-db74-6695-8c6dbaac3547" xlink:to="loc_us-gaap_ShareBasedCompensation_90cbc3ab-f555-6407-b3b4-b2bfa84c9f18" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncreaseDecreaseInAllowanceForEquityFundsUsedDuringConstruction" xlink:label="loc_us-gaap_IncreaseDecreaseInAllowanceForEquityFundsUsedDuringConstruction_36139392-3005-eba9-82e9-7624c4ed3832" xlink:type="locator" />
    <link:calculationArc order="11" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations_fd33978d-50b8-db74-6695-8c6dbaac3547" xlink:to="loc_us-gaap_IncreaseDecreaseInAllowanceForEquityFundsUsedDuringConstruction_36139392-3005-eba9-82e9-7624c4ed3832" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncreaseDecreaseInOtherOperatingAssets" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssets_d54a644c-3d3c-bcc1-da30-2f136651f90f" xlink:type="locator" />
    <link:calculationArc order="12" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations_fd33978d-50b8-db74-6695-8c6dbaac3547" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssets_d54a644c-3d3c-bcc1-da30-2f136651f90f" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncreaseDecreaseInOtherOperatingLiabilities" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherOperatingLiabilities_a039d388-4db8-a076-4618-28899f6ce801" xlink:type="locator" />
    <link:calculationArc order="13" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations_fd33978d-50b8-db74-6695-8c6dbaac3547" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherOperatingLiabilities_a039d388-4db8-a076-4618-28899f6ce801" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperations" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperations_d2bc8fb4-8ebc-76d6-9ba9-10685e994440" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ProceedsFromIssuanceOfCommonStock" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfCommonStock_6ec8bc8e-bcd9-36ad-d8ae-2c2fa1dfd920" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperations_d2bc8fb4-8ebc-76d6-9ba9-10685e994440" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfCommonStock_6ec8bc8e-bcd9-36ad-d8ae-2c2fa1dfd920" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ProceedsFromContributionsFromParent" xlink:label="loc_us-gaap_ProceedsFromContributionsFromParent_24983363-084f-af9b-73b5-01883f18ad71" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperations_d2bc8fb4-8ebc-76d6-9ba9-10685e994440" xlink:to="loc_us-gaap_ProceedsFromContributionsFromParent_24983363-084f-af9b-73b5-01883f18ad71" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PaymentsOfDividendsCommonStock" xlink:label="loc_us-gaap_PaymentsOfDividendsCommonStock_15de0c29-7f29-fc68-dcff-36f8e7ff06d8" xlink:type="locator" />
    <link:calculationArc order="3" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperations_d2bc8fb4-8ebc-76d6-9ba9-10685e994440" xlink:to="loc_us-gaap_PaymentsOfDividendsCommonStock_15de0c29-7f29-fc68-dcff-36f8e7ff06d8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ProceedsFromIssuanceOfLongTermDebt" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfLongTermDebt_60ab1096-bf53-5d61-76bd-431fe857fc03" xlink:type="locator" />
    <link:calculationArc order="4" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperations_d2bc8fb4-8ebc-76d6-9ba9-10685e994440" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfLongTermDebt_60ab1096-bf53-5d61-76bd-431fe857fc03" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RepaymentsOfLongTermDebt" xlink:label="loc_us-gaap_RepaymentsOfLongTermDebt_cfa1e746-5920-c3b5-33ed-a7dee018f26c" xlink:type="locator" />
    <link:calculationArc order="5" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperations_d2bc8fb4-8ebc-76d6-9ba9-10685e994440" xlink:to="loc_us-gaap_RepaymentsOfLongTermDebt_cfa1e746-5920-c3b5-33ed-a7dee018f26c" xlink:type="arc" />
    <link:loc xlink:href="swx-20181231.xsd#swx_ProceedsFromRepaymentsOfLinesOfCreditAndCommercialPaper" xlink:label="loc_swx_ProceedsFromRepaymentsOfLinesOfCreditAndCommercialPaper_99b9b419-3113-c30b-9357-0e712b813c39" xlink:type="locator" />
    <link:calculationArc order="6" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperations_d2bc8fb4-8ebc-76d6-9ba9-10685e994440" xlink:to="loc_swx_ProceedsFromRepaymentsOfLinesOfCreditAndCommercialPaper_99b9b419-3113-c30b-9357-0e712b813c39" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ProceedsFromRepaymentsOfShortTermDebt" xlink:label="loc_us-gaap_ProceedsFromRepaymentsOfShortTermDebt_0ad26e66-f00d-eb22-5d27-4b24aacf3047" xlink:type="locator" />
    <link:calculationArc order="7" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperations_d2bc8fb4-8ebc-76d6-9ba9-10685e994440" xlink:to="loc_us-gaap_ProceedsFromRepaymentsOfShortTermDebt_0ad26e66-f00d-eb22-5d27-4b24aacf3047" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation" xlink:label="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_43305c85-41ff-3d0f-c464-dc8983363bce" xlink:type="locator" />
    <link:calculationArc order="8" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperations_d2bc8fb4-8ebc-76d6-9ba9-10685e994440" xlink:to="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_43305c85-41ff-3d0f-c464-dc8983363bce" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ProceedsFromPaymentsForOtherFinancingActivities" xlink:label="loc_us-gaap_ProceedsFromPaymentsForOtherFinancingActivities_38e7f3e2-9d1a-8772-e4aa-fb2cb7d8adc0" xlink:type="locator" />
    <link:calculationArc order="9" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperations_d2bc8fb4-8ebc-76d6-9ba9-10685e994440" xlink:to="loc_us-gaap_ProceedsFromPaymentsForOtherFinancingActivities_38e7f3e2-9d1a-8772-e4aa-fb2cb7d8adc0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations_11e67a5b-b991-9b9e-ce71-4134920b3689" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PaymentsToAcquirePropertyPlantAndEquipment" xlink:label="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_6d89f221-3ede-36b2-fcad-4a4ce1606f6a" xlink:type="locator" />
    <link:calculationArc order="1" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations_11e67a5b-b991-9b9e-ce71-4134920b3689" xlink:to="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_6d89f221-3ede-36b2-fcad-4a4ce1606f6a" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncreaseDecreaseInCustomerAdvances" xlink:label="loc_us-gaap_IncreaseDecreaseInCustomerAdvances_55b937d4-dc8f-84c7-500b-9e181b0b0546" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations_11e67a5b-b991-9b9e-ce71-4134920b3689" xlink:to="loc_us-gaap_IncreaseDecreaseInCustomerAdvances_55b937d4-dc8f-84c7-500b-9e181b0b0546" xlink:type="arc" />
    <link:loc xlink:href="swx-20181231.xsd#swx_ProceedsFromMiscellaneousInvestingActivities" xlink:label="loc_swx_ProceedsFromMiscellaneousInvestingActivities_40f23d9d-54ff-c0b1-9dc3-0e712b87e875" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations_11e67a5b-b991-9b9e-ce71-4134920b3689" xlink:to="loc_swx_ProceedsFromMiscellaneousInvestingActivities_40f23d9d-54ff-c0b1-9dc3-0e712b87e875" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ProceedsFromDividendsReceived" xlink:label="loc_us-gaap_ProceedsFromDividendsReceived_d8d96b06-7fbe-1fd3-e2eb-069fdfd533ee" xlink:type="locator" />
    <link:calculationArc order="4" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations_11e67a5b-b991-9b9e-ce71-4134920b3689" xlink:to="loc_us-gaap_ProceedsFromDividendsReceived_d8d96b06-7fbe-1fd3-e2eb-069fdfd533ee" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_9743d583-dfae-6ae9-f133-a1e331df792c" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents" xlink:label="loc_us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_714a30d1-878f-1497-8ad1-4b1e113da228" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_9743d583-dfae-6ae9-f133-a1e331df792c" xlink:to="loc_us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_714a30d1-878f-1497-8ad1-4b1e113da228" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_d8917e24-06dd-060d-a290-e426c7895e54" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_9743d583-dfae-6ae9-f133-a1e331df792c" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_d8917e24-06dd-060d-a290-e426c7895e54" xlink:type="arc" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_d8917e24-06dd-060d-a290-e426c7895e54" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfCommonStock_6ec8bc8e-bcd9-36ad-d8ae-2c2fa1dfd920" xlink:type="arc" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_d8917e24-06dd-060d-a290-e426c7895e54" xlink:to="loc_us-gaap_ProceedsFromContributionsFromParent_24983363-084f-af9b-73b5-01883f18ad71" xlink:type="arc" />
    <link:calculationArc order="3" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_d8917e24-06dd-060d-a290-e426c7895e54" xlink:to="loc_us-gaap_PaymentsOfDividendsCommonStock_15de0c29-7f29-fc68-dcff-36f8e7ff06d8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PaymentsOfDividendsMinorityInterest" xlink:label="loc_us-gaap_PaymentsOfDividendsMinorityInterest_69563a84-74b9-c6d2-b331-4b99188223c3" xlink:type="locator" />
    <link:calculationArc order="4" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_d8917e24-06dd-060d-a290-e426c7895e54" xlink:to="loc_us-gaap_PaymentsOfDividendsMinorityInterest_69563a84-74b9-c6d2-b331-4b99188223c3" xlink:type="arc" />
    <link:calculationArc order="5" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_d8917e24-06dd-060d-a290-e426c7895e54" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfLongTermDebt_60ab1096-bf53-5d61-76bd-431fe857fc03" xlink:type="arc" />
    <link:calculationArc order="6" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_d8917e24-06dd-060d-a290-e426c7895e54" xlink:to="loc_us-gaap_RepaymentsOfLongTermDebt_cfa1e746-5920-c3b5-33ed-a7dee018f26c" xlink:type="arc" />
    <link:calculationArc order="7" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_d8917e24-06dd-060d-a290-e426c7895e54" xlink:to="loc_swx_ProceedsFromRepaymentsOfLinesOfCreditAndCommercialPaper_99b9b419-3113-c30b-9357-0e712b813c39" xlink:type="arc" />
    <link:calculationArc order="8" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_d8917e24-06dd-060d-a290-e426c7895e54" xlink:to="loc_us-gaap_ProceedsFromRepaymentsOfShortTermDebt_0ad26e66-f00d-eb22-5d27-4b24aacf3047" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RepaymentsOfDebtAndCapitalLeaseObligations" xlink:label="loc_us-gaap_RepaymentsOfDebtAndCapitalLeaseObligations_a0ee1c92-694f-57df-c681-1cbde8a8ed83" xlink:type="locator" />
    <link:calculationArc order="9" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_d8917e24-06dd-060d-a290-e426c7895e54" xlink:to="loc_us-gaap_RepaymentsOfDebtAndCapitalLeaseObligations_a0ee1c92-694f-57df-c681-1cbde8a8ed83" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PaymentsForRepurchaseOfRedeemableNoncontrollingInterest" xlink:label="loc_us-gaap_PaymentsForRepurchaseOfRedeemableNoncontrollingInterest_508033ef-bf02-d8fd-b487-a6aa4c7819dd" xlink:type="locator" />
    <link:calculationArc order="10" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_d8917e24-06dd-060d-a290-e426c7895e54" xlink:to="loc_us-gaap_PaymentsForRepurchaseOfRedeemableNoncontrollingInterest_508033ef-bf02-d8fd-b487-a6aa4c7819dd" xlink:type="arc" />
    <link:calculationArc order="11" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_d8917e24-06dd-060d-a290-e426c7895e54" xlink:to="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_43305c85-41ff-3d0f-c464-dc8983363bce" xlink:type="arc" />
    <link:calculationArc order="12" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_d8917e24-06dd-060d-a290-e426c7895e54" xlink:to="loc_us-gaap_ProceedsFromPaymentsForOtherFinancingActivities_38e7f3e2-9d1a-8772-e4aa-fb2cb7d8adc0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_1bd0bd4e-4a6f-b052-029c-0ecb0c520251" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_9743d583-dfae-6ae9-f133-a1e331df792c" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_1bd0bd4e-4a6f-b052-029c-0ecb0c520251" xlink:type="arc" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_1bd0bd4e-4a6f-b052-029c-0ecb0c520251" xlink:to="loc_us-gaap_DepreciationAndAmortization_97b88949-d4fc-dff4-be7f-d39018557f4e" xlink:type="arc" />
    <link:calculationArc order="2" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_1bd0bd4e-4a6f-b052-029c-0ecb0c520251" xlink:to="loc_us-gaap_IncreaseDecreaseInDeferredIncomeTaxes_852a0148-80e8-01e7-45e2-04986579e466" xlink:type="arc" />
    <link:calculationArc order="3" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_1bd0bd4e-4a6f-b052-029c-0ecb0c520251" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_5f96c19e-85fe-99f6-cec0-c2c9d7470ed4" xlink:type="arc" />
    <link:calculationArc order="4" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_1bd0bd4e-4a6f-b052-029c-0ecb0c520251" xlink:to="loc_us-gaap_IncreaseDecreaseInUnbilledReceivables_41adfb2c-6577-a630-96b7-f1964f7d3890" xlink:type="arc" />
    <link:calculationArc order="5" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_1bd0bd4e-4a6f-b052-029c-0ecb0c520251" xlink:to="loc_us-gaap_IncreaseDecreaseInDeferredGasCost_a79f3c72-fa61-8e2b-9bcb-436c1f546e77" xlink:type="arc" />
    <link:calculationArc order="6" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_1bd0bd4e-4a6f-b052-029c-0ecb0c520251" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsPayable_0a39d2ee-656d-ead5-a676-41794b4da8f4" xlink:type="arc" />
    <link:calculationArc order="7" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_1bd0bd4e-4a6f-b052-029c-0ecb0c520251" xlink:to="loc_us-gaap_IncreaseDecreaseInAccruedTaxesPayable_7b3c76f4-f4f7-d8c9-23c6-b259dabda37e" xlink:type="arc" />
    <link:calculationArc order="8" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_1bd0bd4e-4a6f-b052-029c-0ecb0c520251" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherCurrentAssetsAndLiabilitiesNet_27004e54-27fb-868f-b1d8-f8874a01e9b6" xlink:type="arc" />
    <link:calculationArc order="9" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_1bd0bd4e-4a6f-b052-029c-0ecb0c520251" xlink:to="loc_us-gaap_ShareBasedCompensation_90cbc3ab-f555-6407-b3b4-b2bfa84c9f18" xlink:type="arc" />
    <link:calculationArc order="10" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_1bd0bd4e-4a6f-b052-029c-0ecb0c520251" xlink:to="loc_us-gaap_IncreaseDecreaseInAllowanceForEquityFundsUsedDuringConstruction_36139392-3005-eba9-82e9-7624c4ed3832" xlink:type="arc" />
    <link:calculationArc order="11" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_1bd0bd4e-4a6f-b052-029c-0ecb0c520251" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssets_d54a644c-3d3c-bcc1-da30-2f136651f90f" xlink:type="arc" />
    <link:calculationArc order="12" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_1bd0bd4e-4a6f-b052-029c-0ecb0c520251" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherOperatingLiabilities_a039d388-4db8-a076-4618-28899f6ce801" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_GainLossOnSaleOfPropertyPlantEquipment" xlink:label="loc_us-gaap_GainLossOnSaleOfPropertyPlantEquipment_ef1b7738-192b-a4ca-6396-5577f303c271" xlink:type="locator" />
    <link:calculationArc order="13" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_1bd0bd4e-4a6f-b052-029c-0ecb0c520251" xlink:to="loc_us-gaap_GainLossOnSaleOfPropertyPlantEquipment_ef1b7738-192b-a4ca-6396-5577f303c271" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ProfitLoss" xlink:label="loc_us-gaap_ProfitLoss_8aa68cfb-2df7-9a23-d1ed-4fe33385b4a2" xlink:type="locator" />
    <link:calculationArc order="14" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_1bd0bd4e-4a6f-b052-029c-0ecb0c520251" xlink:to="loc_us-gaap_ProfitLoss_8aa68cfb-2df7-9a23-d1ed-4fe33385b4a2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_28655e34-499f-b7bf-c54f-5de0990d0c65" xlink:type="locator" />
    <link:calculationArc order="4" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_9743d583-dfae-6ae9-f133-a1e331df792c" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_28655e34-499f-b7bf-c54f-5de0990d0c65" xlink:type="arc" />
    <link:calculationArc order="1" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_28655e34-499f-b7bf-c54f-5de0990d0c65" xlink:to="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_6d89f221-3ede-36b2-fcad-4a4ce1606f6a" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_80abba07-181c-6ed2-349d-9d7dfc078eab" xlink:type="locator" />
    <link:calculationArc order="2" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_28655e34-499f-b7bf-c54f-5de0990d0c65" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_80abba07-181c-6ed2-349d-9d7dfc078eab" xlink:type="arc" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_28655e34-499f-b7bf-c54f-5de0990d0c65" xlink:to="loc_us-gaap_IncreaseDecreaseInCustomerAdvances_55b937d4-dc8f-84c7-500b-9e181b0b0546" xlink:type="arc" />
    <link:calculationArc order="4" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_28655e34-499f-b7bf-c54f-5de0990d0c65" xlink:to="loc_swx_ProceedsFromMiscellaneousInvestingActivities_40f23d9d-54ff-c0b1-9dc3-0e712b87e875" xlink:type="arc" />
    <link:calculationArc order="5" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_28655e34-499f-b7bf-c54f-5de0990d0c65" xlink:to="loc_us-gaap_ProceedsFromDividendsReceived_d8d96b06-7fbe-1fd3-e2eb-069fdfd533ee" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/ConsolidatedStatementsOfCashFlowsCalc2" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_897C46B49D71F72FE2EB2FC8597117B8_9743d583-dfae-6ae9-f133-a1e331df792c" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperations" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperations_897C46B49D71F72FE2EB2FC8597117B8_d2bc8fb4-8ebc-76d6-9ba9-10685e994440" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_897C46B49D71F72FE2EB2FC8597117B8_9743d583-dfae-6ae9-f133-a1e331df792c" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperations_897C46B49D71F72FE2EB2FC8597117B8_d2bc8fb4-8ebc-76d6-9ba9-10685e994440" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CashProvidedByUsedInOperatingActivitiesDiscontinuedOperations" xlink:label="loc_us-gaap_CashProvidedByUsedInOperatingActivitiesDiscontinuedOperations_897C46B49D71F72FE2EB2FC8597117B8_1adf41ec-5a2c-64b7-c6ee-ac5a454db672" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_897C46B49D71F72FE2EB2FC8597117B8_9743d583-dfae-6ae9-f133-a1e331df792c" xlink:to="loc_us-gaap_CashProvidedByUsedInOperatingActivitiesDiscontinuedOperations_897C46B49D71F72FE2EB2FC8597117B8_1adf41ec-5a2c-64b7-c6ee-ac5a454db672" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CashProvidedByUsedInInvestingActivitiesDiscontinuedOperations" xlink:label="loc_us-gaap_CashProvidedByUsedInInvestingActivitiesDiscontinuedOperations_897C46B49D71F72FE2EB2FC8597117B8_fd904acb-5ee8-2a8a-63a4-f34fbb4dd5c0" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_897C46B49D71F72FE2EB2FC8597117B8_9743d583-dfae-6ae9-f133-a1e331df792c" xlink:to="loc_us-gaap_CashProvidedByUsedInInvestingActivitiesDiscontinuedOperations_897C46B49D71F72FE2EB2FC8597117B8_fd904acb-5ee8-2a8a-63a4-f34fbb4dd5c0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CashProvidedByUsedInFinancingActivitiesDiscontinuedOperations" xlink:label="loc_us-gaap_CashProvidedByUsedInFinancingActivitiesDiscontinuedOperations_897C46B49D71F72FE2EB2FC8597117B8_0293a5ac-226d-5172-9d77-f89f36a9a621" xlink:type="locator" />
    <link:calculationArc order="4" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_897C46B49D71F72FE2EB2FC8597117B8_9743d583-dfae-6ae9-f133-a1e331df792c" xlink:to="loc_us-gaap_CashProvidedByUsedInFinancingActivitiesDiscontinuedOperations_897C46B49D71F72FE2EB2FC8597117B8_0293a5ac-226d-5172-9d77-f89f36a9a621" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsDisposalGroupIncludingDiscontinuedOperations" xlink:label="loc_us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsDisposalGroupIncludingDiscontinuedOperations_897C46B49D71F72FE2EB2FC8597117B8_e1910761-7cf9-47ab-19d6-3846e901dfa0" xlink:type="locator" />
    <link:calculationArc order="5" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_897C46B49D71F72FE2EB2FC8597117B8_9743d583-dfae-6ae9-f133-a1e331df792c" xlink:to="loc_us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsDisposalGroupIncludingDiscontinuedOperations_897C46B49D71F72FE2EB2FC8597117B8_e1910761-7cf9-47ab-19d6-3846e901dfa0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations_897C46B49D71F72FE2EB2FC8597117B8_fd33978d-50b8-db74-6695-8c6dbaac3547" xlink:type="locator" />
    <link:calculationArc order="6" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_897C46B49D71F72FE2EB2FC8597117B8_9743d583-dfae-6ae9-f133-a1e331df792c" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations_897C46B49D71F72FE2EB2FC8597117B8_fd33978d-50b8-db74-6695-8c6dbaac3547" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations_897C46B49D71F72FE2EB2FC8597117B8_11e67a5b-b991-9b9e-ce71-4134920b3689" xlink:type="locator" />
    <link:calculationArc order="7" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_897C46B49D71F72FE2EB2FC8597117B8_9743d583-dfae-6ae9-f133-a1e331df792c" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations_897C46B49D71F72FE2EB2FC8597117B8_11e67a5b-b991-9b9e-ce71-4134920b3689" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/ConsolidatedStatementsOfComprehensiveIncome" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ComprehensiveIncomeNetOfTax" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTax_cf605d39-9067-2f07-a6b5-7dfa6481009e" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest_0e67d263-6e0f-cbd4-f553-6c8cebeb68d8" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_ComprehensiveIncomeNetOfTax_cf605d39-9067-2f07-a6b5-7dfa6481009e" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest_0e67d263-6e0f-cbd4-f553-6c8cebeb68d8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_e68ce304-18e4-96c0-3260-363a872863db" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest_0e67d263-6e0f-cbd4-f553-6c8cebeb68d8" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_e68ce304-18e4-96c0-3260-363a872863db" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax_e83cd656-9fce-43ca-6f7c-1be78bef4068" xlink:type="locator" />
    <link:calculationArc order="1" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_e68ce304-18e4-96c0-3260-363a872863db" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax_e83cd656-9fce-43ca-6f7c-1be78bef4068" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax_254de926-c784-5333-b3ea-41e5ac110b5c" xlink:type="locator" />
    <link:calculationArc order="1" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax_e83cd656-9fce-43ca-6f7c-1be78bef4068" xlink:to="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax_254de926-c784-5333-b3ea-41e5ac110b5c" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditNetOfTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditNetOfTax_df6ca9c6-9b90-b610-354f-a75a1a563b7b" xlink:type="locator" />
    <link:calculationArc order="2" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax_e83cd656-9fce-43ca-6f7c-1be78bef4068" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditNetOfTax_df6ca9c6-9b90-b610-354f-a75a1a563b7b" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax_692e22e6-3994-7bbf-3051-c279fe8930ff" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax_e83cd656-9fce-43ca-6f7c-1be78bef4068" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax_692e22e6-3994-7bbf-3051-c279fe8930ff" xlink:type="arc" />
    <link:loc xlink:href="swx-20181231.xsd#swx_OtherComprehensiveIncomeDefinedBenefitPlansRegulatoryAdjustmentNetOfTax" xlink:label="loc_swx_OtherComprehensiveIncomeDefinedBenefitPlansRegulatoryAdjustmentNetOfTax_875ff6f8-f88a-15ba-9e26-0e712b85b96a" xlink:type="locator" />
    <link:calculationArc order="4" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax_e83cd656-9fce-43ca-6f7c-1be78bef4068" xlink:to="loc_swx_OtherComprehensiveIncomeDefinedBenefitPlansRegulatoryAdjustmentNetOfTax_875ff6f8-f88a-15ba-9e26-0e712b85b96a" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax_f44275a4-2994-4281-73e3-0fa77d53374b" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_e68ce304-18e4-96c0-3260-363a872863db" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax_f44275a4-2994-4281-73e3-0fa77d53374b" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_b087c8bb-e0f6-4c7f-883c-027f52d32745" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_e68ce304-18e4-96c0-3260-363a872863db" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_b087c8bb-e0f6-4c7f-883c-027f52d32745" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ProfitLoss" xlink:label="loc_us-gaap_ProfitLoss_8aa68cfb-2df7-9a23-d1ed-4fe33385b4a2" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest_0e67d263-6e0f-cbd4-f553-6c8cebeb68d8" xlink:to="loc_us-gaap_ProfitLoss_8aa68cfb-2df7-9a23-d1ed-4fe33385b4a2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest_ff106bf5-082b-8f58-cc36-c7f91866b7d3" xlink:type="locator" />
    <link:calculationArc order="2" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_ComprehensiveIncomeNetOfTax_cf605d39-9067-2f07-a6b5-7dfa6481009e" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest_ff106bf5-082b-8f58-cc36-c7f91866b7d3" xlink:type="arc" />
    <link:loc xlink:href="swx-20181231.xsd#swx_OtherComprehensiveIncomeLossFromDiscontinuedOperationNetOfTax" xlink:label="loc_swx_OtherComprehensiveIncomeLossFromDiscontinuedOperationNetOfTax_5af7c570-1e1c-33e0-451f-0e712b85eee4" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_ComprehensiveIncomeNetOfTax_cf605d39-9067-2f07-a6b5-7dfa6481009e" xlink:to="loc_swx_OtherComprehensiveIncomeLossFromDiscontinuedOperationNetOfTax_5af7c570-1e1c-33e0-451f-0e712b85eee4" xlink:type="arc" />
    <link:loc xlink:href="swx-20181231.xsd#swx_ComprehensiveIncomeFromDiscontinuedOperationNetOfTaxIncludingPortionAttributableToNoncontrollingInterest" xlink:label="loc_swx_ComprehensiveIncomeFromDiscontinuedOperationNetOfTaxIncludingPortionAttributableToNoncontrollingInterest_0f89910f-3ec9-76f6-b933-0e712b782f27" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_swx_OtherComprehensiveIncomeLossFromDiscontinuedOperationNetOfTax_5af7c570-1e1c-33e0-451f-0e712b85eee4" xlink:to="loc_swx_ComprehensiveIncomeFromDiscontinuedOperationNetOfTaxIncludingPortionAttributableToNoncontrollingInterest_0f89910f-3ec9-76f6-b933-0e712b782f27" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity" xlink:label="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity_5b931a9a-8475-ddfa-f7f0-ce511990c1b0" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_swx_ComprehensiveIncomeFromDiscontinuedOperationNetOfTaxIncludingPortionAttributableToNoncontrollingInterest_0f89910f-3ec9-76f6-b933-0e712b782f27" xlink:to="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity_5b931a9a-8475-ddfa-f7f0-ce511990c1b0" xlink:type="arc" />
    <link:loc xlink:href="swx-20181231.xsd#swx_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentFromDiscontinuedOperationNetOfTaxPortionAttributableToParent" xlink:label="loc_swx_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentFromDiscontinuedOperationNetOfTaxPortionAttributableToParent_8ccd3588-4cac-a9f4-8b1d-0e712b7bcd63" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_swx_ComprehensiveIncomeFromDiscontinuedOperationNetOfTaxIncludingPortionAttributableToNoncontrollingInterest_0f89910f-3ec9-76f6-b933-0e712b782f27" xlink:to="loc_swx_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentFromDiscontinuedOperationNetOfTaxPortionAttributableToParent_8ccd3588-4cac-a9f4-8b1d-0e712b7bcd63" xlink:type="arc" />
    <link:loc xlink:href="swx-20181231.xsd#swx_OtherComprehensiveIncomeLossFromDiscontinuedOperationNetOfTaxPortionAttributableToNoncontrollingInterest" xlink:label="loc_swx_OtherComprehensiveIncomeLossFromDiscontinuedOperationNetOfTaxPortionAttributableToNoncontrollingInterest_9C9A91965FF96B4959326122DA18DF24" xlink:type="locator" />
    <link:calculationArc order="2" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_swx_OtherComprehensiveIncomeLossFromDiscontinuedOperationNetOfTax_5af7c570-1e1c-33e0-451f-0e712b85eee4" xlink:to="loc_swx_OtherComprehensiveIncomeLossFromDiscontinuedOperationNetOfTaxPortionAttributableToNoncontrollingInterest_9C9A91965FF96B4959326122DA18DF24" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/ConsolidatedStatementsOfComprehensiveIncomeCalc2" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest_1223344BB83DEDA233FE2FF5D07D05D1_0e67d263-6e0f-cbd4-f553-6c8cebeb68d8" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest_1223344BB83DEDA233FE2FF5D07D05D1_98ad2198-806f-6053-5326-b79be5cbb9ef" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest_1223344BB83DEDA233FE2FF5D07D05D1_0e67d263-6e0f-cbd4-f553-6c8cebeb68d8" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest_1223344BB83DEDA233FE2FF5D07D05D1_98ad2198-806f-6053-5326-b79be5cbb9ef" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_1223344BB83DEDA233FE2FF5D07D05D1_e68ce304-18e4-96c0-3260-363a872863db" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest_1223344BB83DEDA233FE2FF5D07D05D1_0e67d263-6e0f-cbd4-f553-6c8cebeb68d8" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_1223344BB83DEDA233FE2FF5D07D05D1_e68ce304-18e4-96c0-3260-363a872863db" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/ConsolidatedStatementsOfEquityAndRedeemableNoncontrollingInterest" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/ConsolidatedStatementsOfEquityAndRedeemableNoncontrollingInterestParenthetical" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/ConsolidatedStatementsOfIncome" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="loc_us-gaap_NetIncomeLoss_a10eea14-f4db-3125-d183-77bb54500e95" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest_98ad2198-806f-6053-5326-b79be5cbb9ef" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetIncomeLoss_a10eea14-f4db-3125-d183-77bb54500e95" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest_98ad2198-806f-6053-5326-b79be5cbb9ef" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_4d8b6d19-6a54-06aa-2077-c10380bd20d1" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest_98ad2198-806f-6053-5326-b79be5cbb9ef" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_4d8b6d19-6a54-06aa-2077-c10380bd20d1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingIncomeLoss" xlink:label="loc_us-gaap_OperatingIncomeLoss_5c890570-5904-7978-36d8-35b96dcf45ab" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_4d8b6d19-6a54-06aa-2077-c10380bd20d1" xlink:to="loc_us-gaap_OperatingIncomeLoss_5c890570-5904-7978-36d8-35b96dcf45ab" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RegulatedAndUnregulatedOperatingRevenue" xlink:label="loc_us-gaap_RegulatedAndUnregulatedOperatingRevenue_ff9ef388-581a-a2fb-2963-e99dae0a4918" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingIncomeLoss_5c890570-5904-7978-36d8-35b96dcf45ab" xlink:to="loc_us-gaap_RegulatedAndUnregulatedOperatingRevenue_ff9ef388-581a-a2fb-2963-e99dae0a4918" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_4562fc03-cbaf-a89b-d454-b9d16c5936b8" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_RegulatedAndUnregulatedOperatingRevenue_ff9ef388-581a-a2fb-2963-e99dae0a4918" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_4562fc03-cbaf-a89b-d454-b9d16c5936b8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RegulatedOperatingRevenueGas" xlink:label="loc_us-gaap_RegulatedOperatingRevenueGas_b175b957-2266-28b0-f418-63a2a0f1cb17" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_RegulatedAndUnregulatedOperatingRevenue_ff9ef388-581a-a2fb-2963-e99dae0a4918" xlink:to="loc_us-gaap_RegulatedOperatingRevenueGas_b175b957-2266-28b0-f418-63a2a0f1cb17" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CostsAndExpenses" xlink:label="loc_us-gaap_CostsAndExpenses_8823ccfd-55af-348e-39a2-91433072d2c9" xlink:type="locator" />
    <link:calculationArc order="2" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingIncomeLoss_5c890570-5904-7978-36d8-35b96dcf45ab" xlink:to="loc_us-gaap_CostsAndExpenses_8823ccfd-55af-348e-39a2-91433072d2c9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_UtilitiesOperatingExpenseGasAndPetroleumPurchased" xlink:label="loc_us-gaap_UtilitiesOperatingExpenseGasAndPetroleumPurchased_2c20608e-a05a-d69a-f88b-a0d34a73f4c1" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CostsAndExpenses_8823ccfd-55af-348e-39a2-91433072d2c9" xlink:to="loc_us-gaap_UtilitiesOperatingExpenseGasAndPetroleumPurchased_2c20608e-a05a-d69a-f88b-a0d34a73f4c1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_UtilitiesOperatingExpenseMaintenanceAndOperations" xlink:label="loc_us-gaap_UtilitiesOperatingExpenseMaintenanceAndOperations_fbcdc3ac-66af-2fd3-5bb7-db4832224688" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CostsAndExpenses_8823ccfd-55af-348e-39a2-91433072d2c9" xlink:to="loc_us-gaap_UtilitiesOperatingExpenseMaintenanceAndOperations_fbcdc3ac-66af-2fd3-5bb7-db4832224688" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DepreciationAndAmortization" xlink:label="loc_us-gaap_DepreciationAndAmortization_97b88949-d4fc-dff4-be7f-d39018557f4e" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CostsAndExpenses_8823ccfd-55af-348e-39a2-91433072d2c9" xlink:to="loc_us-gaap_DepreciationAndAmortization_97b88949-d4fc-dff4-be7f-d39018557f4e" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TaxesExcludingIncomeAndExciseTaxes" xlink:label="loc_us-gaap_TaxesExcludingIncomeAndExciseTaxes_c2403a48-8c07-df78-0759-fb2d2cf1986f" xlink:type="locator" />
    <link:calculationArc order="4" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CostsAndExpenses_8823ccfd-55af-348e-39a2-91433072d2c9" xlink:to="loc_us-gaap_TaxesExcludingIncomeAndExciseTaxes_c2403a48-8c07-df78-0759-fb2d2cf1986f" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CostOfGoodsAndServicesSold" xlink:label="loc_us-gaap_CostOfGoodsAndServicesSold_1c65a201-fd8e-32d7-dad9-c6d1d5719594" xlink:type="locator" />
    <link:calculationArc order="5" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CostsAndExpenses_8823ccfd-55af-348e-39a2-91433072d2c9" xlink:to="loc_us-gaap_CostOfGoodsAndServicesSold_1c65a201-fd8e-32d7-dad9-c6d1d5719594" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NonoperatingIncomeExpense" xlink:label="loc_us-gaap_NonoperatingIncomeExpense_c5398800-6e68-ed86-a47c-16106e0730c2" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_4d8b6d19-6a54-06aa-2077-c10380bd20d1" xlink:to="loc_us-gaap_NonoperatingIncomeExpense_c5398800-6e68-ed86-a47c-16106e0730c2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_InterestExpense" xlink:label="loc_us-gaap_InterestExpense_a56b34b7-57ab-a07c-7f03-8366849a14f0" xlink:type="locator" />
    <link:calculationArc order="1" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NonoperatingIncomeExpense_c5398800-6e68-ed86-a47c-16106e0730c2" xlink:to="loc_us-gaap_InterestExpense_a56b34b7-57ab-a07c-7f03-8366849a14f0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherNonoperatingIncomeExpense" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_41e96f8d-e499-8de8-69a8-27f1c7d4df6e" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NonoperatingIncomeExpense_c5398800-6e68-ed86-a47c-16106e0730c2" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_41e96f8d-e499-8de8-69a8-27f1c7d4df6e" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeTaxExpenseBenefit" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_97bbae57-7f84-4da9-acab-610e56204929" xlink:type="locator" />
    <link:calculationArc order="2" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest_98ad2198-806f-6053-5326-b79be5cbb9ef" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_97bbae57-7f84-4da9-acab-610e56204929" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity" xlink:label="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity_5b931a9a-8475-ddfa-f7f0-ce511990c1b0" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetIncomeLoss_a10eea14-f4db-3125-d183-77bb54500e95" xlink:to="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity_5b931a9a-8475-ddfa-f7f0-ce511990c1b0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax" xlink:label="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax_9b451285-adc3-6c37-15b7-4fd2a15bd781" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity_5b931a9a-8475-ddfa-f7f0-ce511990c1b0" xlink:to="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax_9b451285-adc3-6c37-15b7-4fd2a15bd781" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DiscontinuedOperationIncomeLossFromDiscontinuedOperationBeforeIncomeTax" xlink:label="loc_us-gaap_DiscontinuedOperationIncomeLossFromDiscontinuedOperationBeforeIncomeTax_e6c2b52f-6843-2914-0fae-f74995d125a1" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax_9b451285-adc3-6c37-15b7-4fd2a15bd781" xlink:to="loc_us-gaap_DiscontinuedOperationIncomeLossFromDiscontinuedOperationBeforeIncomeTax_e6c2b52f-6843-2914-0fae-f74995d125a1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DiscontinuedOperationTaxEffectOfDiscontinuedOperation" xlink:label="loc_us-gaap_DiscontinuedOperationTaxEffectOfDiscontinuedOperation_925a043d-18b3-5d03-8e0b-c0fb4146cd8c" xlink:type="locator" />
    <link:calculationArc order="2" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax_9b451285-adc3-6c37-15b7-4fd2a15bd781" xlink:to="loc_us-gaap_DiscontinuedOperationTaxEffectOfDiscontinuedOperation_925a043d-18b3-5d03-8e0b-c0fb4146cd8c" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToNoncontrollingInterest" xlink:label="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToNoncontrollingInterest_98c10b37-bcd2-6eb8-f0e0-80d318ea8fc4" xlink:type="locator" />
    <link:calculationArc order="2" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToReportingEntity_5b931a9a-8475-ddfa-f7f0-ce511990c1b0" xlink:to="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToNoncontrollingInterest_98c10b37-bcd2-6eb8-f0e0-80d318ea8fc4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ProfitLoss" xlink:label="loc_us-gaap_ProfitLoss_8aa68cfb-2df7-9a23-d1ed-4fe33385b4a2" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetIncomeLoss_a10eea14-f4db-3125-d183-77bb54500e95" xlink:to="loc_us-gaap_ProfitLoss_8aa68cfb-2df7-9a23-d1ed-4fe33385b4a2" xlink:type="arc" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_ProfitLoss_8aa68cfb-2df7-9a23-d1ed-4fe33385b4a2" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_4d8b6d19-6a54-06aa-2077-c10380bd20d1" xlink:type="arc" />
    <link:calculationArc order="2" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_ProfitLoss_8aa68cfb-2df7-9a23-d1ed-4fe33385b4a2" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_97bbae57-7f84-4da9-acab-610e56204929" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NetIncomeLossAttributableToNoncontrollingInterest" xlink:label="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_f5ae002e-8316-7bc0-1b41-6cd171b53db3" xlink:type="locator" />
    <link:calculationArc order="4" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetIncomeLoss_a10eea14-f4db-3125-d183-77bb54500e95" xlink:to="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_f5ae002e-8316-7bc0-1b41-6cd171b53db3" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/Derivatives" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/DerivativesAmountOfGainOrLossesRecognizedInIncomeOnDerivativesDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/DerivativesFairValuesOfSwapsInConsolidatedBalanceSheetsDetail" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherDerivativesNotDesignatedAsHedgingInstrumentsAtFairValueNet" xlink:label="loc_us-gaap_OtherDerivativesNotDesignatedAsHedgingInstrumentsAtFairValueNet_10bbdd67-63aa-50a9-10a1-0fb581f71a84" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsAssetAtFairValue" xlink:label="loc_us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsAssetAtFairValue_35af27c3-8dfa-06a9-f08e-9beaf1b20e93" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherDerivativesNotDesignatedAsHedgingInstrumentsAtFairValueNet_10bbdd67-63aa-50a9-10a1-0fb581f71a84" xlink:to="loc_us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsAssetAtFairValue_35af27c3-8dfa-06a9-f08e-9beaf1b20e93" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLiabilityAtFairValue" xlink:label="loc_us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLiabilityAtFairValue_8165334c-a5cf-c2b9-11ba-b6400cae9834" xlink:type="locator" />
    <link:calculationArc order="2" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherDerivativesNotDesignatedAsHedgingInstrumentsAtFairValueNet_10bbdd67-63aa-50a9-10a1-0fb581f71a84" xlink:to="loc_us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLiabilityAtFairValue_8165334c-a5cf-c2b9-11ba-b6400cae9834" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/DerivativesNarrativeDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/DerivativesNotionalAmountsUnderSwapsContractsDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/DerivativesPaidToAndReceivedFromCounterpartiesForSettlementsOfMaturedSwapsDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/DerivativesRegulatoryAssetsLiabilitiesOffsettingDerivativesAtFairValueInCondensedConsolidatedBalanceSheetsDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/DerivativesSummaryOfFinancialAssetsAndLiabilitiesAtFairValueDetail" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet" xlink:label="loc_us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet_5fa087a9-72b2-d160-995a-c77b1826f4b3" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DerivativeAssets" xlink:label="loc_us-gaap_DerivativeAssets_082aa8c2-a051-1bb7-d441-a6d93b3f45f4" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet_5fa087a9-72b2-d160-995a-c77b1826f4b3" xlink:to="loc_us-gaap_DerivativeAssets_082aa8c2-a051-1bb7-d441-a6d93b3f45f4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DerivativeLiabilities" xlink:label="loc_us-gaap_DerivativeLiabilities_7e8e10f8-8ddc-2b6a-eea7-ea4d306368a1" xlink:type="locator" />
    <link:calculationArc order="2" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet_5fa087a9-72b2-d160-995a-c77b1826f4b3" xlink:to="loc_us-gaap_DerivativeLiabilities_7e8e10f8-8ddc-2b6a-eea7-ea4d306368a1" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/DerivativesTables" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/DocumentAndEntityInformation" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/IncomeTaxes" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/IncomeTaxesAdditionalInformationDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/IncomeTaxesDeferredTaxAssetsAndLiabilitiesDetail" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredIncomeTaxLiabilitiesNet" xlink:label="loc_us-gaap_DeferredIncomeTaxLiabilitiesNet_d3ba3006-9df7-8186-2eb2-dc5094562cfe" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredTaxAssetsNet" xlink:label="loc_us-gaap_DeferredTaxAssetsNet_476b367a-1ad6-eb34-c01b-595b754b8aa8" xlink:type="locator" />
    <link:calculationArc order="1" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredIncomeTaxLiabilitiesNet_d3ba3006-9df7-8186-2eb2-dc5094562cfe" xlink:to="loc_us-gaap_DeferredTaxAssetsNet_476b367a-1ad6-eb34-c01b-595b754b8aa8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredTaxAssetsTaxCreditCarryforwards" xlink:label="loc_us-gaap_DeferredTaxAssetsTaxCreditCarryforwards_a38b9623-d40d-b02c-d37f-d84fb6a4eac7" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxAssetsNet_476b367a-1ad6-eb34-c01b-595b754b8aa8" xlink:to="loc_us-gaap_DeferredTaxAssetsTaxCreditCarryforwards_a38b9623-d40d-b02c-d37f-d84fb6a4eac7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefits" xlink:label="loc_us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefits_9a653a3a-e258-968f-49ea-6112d232a0c6" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxAssetsNet_476b367a-1ad6-eb34-c01b-595b754b8aa8" xlink:to="loc_us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefits_9a653a3a-e258-968f-49ea-6112d232a0c6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredTaxAssetsTaxCreditCarryforwardsAlternativeMinimumTax" xlink:label="loc_us-gaap_DeferredTaxAssetsTaxCreditCarryforwardsAlternativeMinimumTax_31009ff6-970a-ad7e-0a51-e32c7cd5cf40" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxAssetsNet_476b367a-1ad6-eb34-c01b-595b754b8aa8" xlink:to="loc_us-gaap_DeferredTaxAssetsTaxCreditCarryforwardsAlternativeMinimumTax_31009ff6-970a-ad7e-0a51-e32c7cd5cf40" xlink:type="arc" />
    <link:loc xlink:href="swx-20181231.xsd#swx_DeferredTaxAssetsOperatingLossAndTaxCreditCarryforwardsNet" xlink:label="loc_swx_DeferredTaxAssetsOperatingLossAndTaxCreditCarryforwardsNet_b5b857b3-a8f7-a80f-156c-580e37aaa957" xlink:type="locator" />
    <link:calculationArc order="4" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxAssetsNet_476b367a-1ad6-eb34-c01b-595b754b8aa8" xlink:to="loc_swx_DeferredTaxAssetsOperatingLossAndTaxCreditCarryforwardsNet_b5b857b3-a8f7-a80f-156c-580e37aaa957" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredTaxAssetsDerivativeInstruments" xlink:label="loc_us-gaap_DeferredTaxAssetsDerivativeInstruments_4604f04c-09cf-e521-b77f-af882240df1d" xlink:type="locator" />
    <link:calculationArc order="5" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxAssetsNet_476b367a-1ad6-eb34-c01b-595b754b8aa8" xlink:to="loc_us-gaap_DeferredTaxAssetsDerivativeInstruments_4604f04c-09cf-e521-b77f-af882240df1d" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredTaxAssetsOther" xlink:label="loc_us-gaap_DeferredTaxAssetsOther_0cc13c2f-6b23-b741-4f28-07325c7e7169" xlink:type="locator" />
    <link:calculationArc order="6" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxAssetsNet_476b367a-1ad6-eb34-c01b-595b754b8aa8" xlink:to="loc_us-gaap_DeferredTaxAssetsOther_0cc13c2f-6b23-b741-4f28-07325c7e7169" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredTaxAssetsValuationAllowance" xlink:label="loc_us-gaap_DeferredTaxAssetsValuationAllowance_d9af76c3-a64a-3b37-1d7d-4e9be8c70af6" xlink:type="locator" />
    <link:calculationArc order="7" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxAssetsNet_476b367a-1ad6-eb34-c01b-595b754b8aa8" xlink:to="loc_us-gaap_DeferredTaxAssetsValuationAllowance_d9af76c3-a64a-3b37-1d7d-4e9be8c70af6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredTaxLiabilities" xlink:label="loc_us-gaap_DeferredTaxLiabilities_cee36967-7b64-56b0-03ea-66fbd4d14899" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredIncomeTaxLiabilitiesNet_d3ba3006-9df7-8186-2eb2-dc5094562cfe" xlink:to="loc_us-gaap_DeferredTaxLiabilities_cee36967-7b64-56b0-03ea-66fbd4d14899" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredTaxLiabilitiesPropertyPlantAndEquipment" xlink:label="loc_us-gaap_DeferredTaxLiabilitiesPropertyPlantAndEquipment_4ed01819-014a-ce74-957e-ddc9b0c1d62e" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxLiabilities_cee36967-7b64-56b0-03ea-66fbd4d14899" xlink:to="loc_us-gaap_DeferredTaxLiabilitiesPropertyPlantAndEquipment_4ed01819-014a-ce74-957e-ddc9b0c1d62e" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredTaxLiabilitiesRegulatoryAssetsAndLiabilities" xlink:label="loc_us-gaap_DeferredTaxLiabilitiesRegulatoryAssetsAndLiabilities_2d2c79bb-7453-dd86-7c01-5dde9dc1e43b" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxLiabilities_cee36967-7b64-56b0-03ea-66fbd4d14899" xlink:to="loc_us-gaap_DeferredTaxLiabilitiesRegulatoryAssetsAndLiabilities_2d2c79bb-7453-dd86-7c01-5dde9dc1e43b" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AccumulatedDeferredInvestmentTaxCredit" xlink:label="loc_us-gaap_AccumulatedDeferredInvestmentTaxCredit_7f2990ba-baf2-924c-8532-ab30fa8454a1" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxLiabilities_cee36967-7b64-56b0-03ea-66fbd4d14899" xlink:to="loc_us-gaap_AccumulatedDeferredInvestmentTaxCredit_7f2990ba-baf2-924c-8532-ab30fa8454a1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredTaxLiabilitiesDeferredExpenseDeferredFinancingCosts" xlink:label="loc_us-gaap_DeferredTaxLiabilitiesDeferredExpenseDeferredFinancingCosts_72bd9ba6-dec5-14d1-da5f-f2f780e73231" xlink:type="locator" />
    <link:calculationArc order="4" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxLiabilities_cee36967-7b64-56b0-03ea-66fbd4d14899" xlink:to="loc_us-gaap_DeferredTaxLiabilitiesDeferredExpenseDeferredFinancingCosts_72bd9ba6-dec5-14d1-da5f-f2f780e73231" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsIntangibleAssets" xlink:label="loc_us-gaap_DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsIntangibleAssets_42b61cde-44f6-df44-52b0-1b84b1e28a47" xlink:type="locator" />
    <link:calculationArc order="5" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxLiabilities_cee36967-7b64-56b0-03ea-66fbd4d14899" xlink:to="loc_us-gaap_DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsIntangibleAssets_42b61cde-44f6-df44-52b0-1b84b1e28a47" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredTaxLiabilitiesOther" xlink:label="loc_us-gaap_DeferredTaxLiabilitiesOther_3e7fd080-3ec6-50fa-98f3-b61bc68dbdcf" xlink:type="locator" />
    <link:calculationArc order="6" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredTaxLiabilities_cee36967-7b64-56b0-03ea-66fbd4d14899" xlink:to="loc_us-gaap_DeferredTaxLiabilitiesOther_3e7fd080-3ec6-50fa-98f3-b61bc68dbdcf" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/IncomeTaxesDeferredTaxAssetsAndLiabilitiesDetailCalc2" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredIncomeTaxLiabilitiesNet" xlink:label="loc_us-gaap_DeferredIncomeTaxLiabilitiesNet_7F1EE2F4AC0CF985D2B40B308712EFF5_d3ba3006-9df7-8186-2eb2-dc5094562cfe" xlink:type="locator" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/IncomeTaxesReconciliationOfUSFederalStatutoryRateToConsolidatedEffectiveTaxRateDetail" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_EffectiveIncomeTaxRateContinuingOperations" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_f1b8c80c-fe31-3624-3b0a-70273297561e" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate_51d18bf0-0823-2940-9470-e9bbca486da6" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_f1b8c80c-fe31-3624-3b0a-70273297561e" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate_51d18bf0-0823-2940-9470-e9bbca486da6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes_d23dd313-f50b-59fa-fd80-0dbe24277535" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_f1b8c80c-fe31-3624-3b0a-70273297561e" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes_d23dd313-f50b-59fa-fd80-0dbe24277535" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationTaxCredits" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationTaxCredits_928f8c54-624a-8542-b4e3-59da2a4e6af6" xlink:type="locator" />
    <link:calculationArc order="3" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_f1b8c80c-fe31-3624-3b0a-70273297561e" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationTaxCredits_928f8c54-624a-8542-b4e3-59da2a4e6af6" xlink:type="arc" />
    <link:loc xlink:href="swx-20181231.xsd#swx_EffectiveIncomeTaxRateReconciliationCompanyOwnedLifeInsurance" xlink:label="loc_swx_EffectiveIncomeTaxRateReconciliationCompanyOwnedLifeInsurance_b3d38117-e23d-c079-a048-580e3973bf66" xlink:type="locator" />
    <link:calculationArc order="4" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_f1b8c80c-fe31-3624-3b0a-70273297561e" xlink:to="loc_swx_EffectiveIncomeTaxRateReconciliationCompanyOwnedLifeInsurance_b3d38117-e23d-c079-a048-580e3973bf66" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationChangeInEnactedTaxRate" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationChangeInEnactedTaxRate_7ffe16d1-cedd-985f-c95d-65ae6fa8d756" xlink:type="locator" />
    <link:calculationArc order="5" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_f1b8c80c-fe31-3624-3b0a-70273297561e" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationChangeInEnactedTaxRate_7ffe16d1-cedd-985f-c95d-65ae6fa8d756" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationOtherAdjustments" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationOtherAdjustments_00f37689-1982-1c68-c80b-43003f810247" xlink:type="locator" />
    <link:calculationArc order="6" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_f1b8c80c-fe31-3624-3b0a-70273297561e" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationOtherAdjustments_00f37689-1982-1c68-c80b-43003f810247" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/IncomeTaxesReconciliationOfUnrecognizedTaxBenefitsDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/IncomeTaxesSignificantComponentsOfDeferredIncomeTaxExpenseBenefitDetail" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredIncomeTaxExpenseBenefit" xlink:label="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_e8a9abf2-38d3-77d1-fb6b-693fef632294" xlink:type="locator" />
    <link:loc xlink:href="swx-20181231.xsd#swx_DeferredFederalAndStateIncomeTaxExpenseBenefit" xlink:label="loc_swx_DeferredFederalAndStateIncomeTaxExpenseBenefit_b287ffd1-4458-03db-b7d2-580e3866e816" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_e8a9abf2-38d3-77d1-fb6b-693fef632294" xlink:to="loc_swx_DeferredFederalAndStateIncomeTaxExpenseBenefit_b287ffd1-4458-03db-b7d2-580e3866e816" xlink:type="arc" />
    <link:loc xlink:href="swx-20181231.xsd#swx_DeferredInvestmentTaxCreditNet" xlink:label="loc_swx_DeferredInvestmentTaxCreditNet_C9A13F4A90CAC018B95C716248A86E72" xlink:type="locator" />
    <link:calculationArc order="2" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_e8a9abf2-38d3-77d1-fb6b-693fef632294" xlink:to="loc_swx_DeferredInvestmentTaxCreditNet_C9A13F4A90CAC018B95C716248A86E72" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/IncomeTaxesSummaryOfIncomeBeforeTaxesAndNoncontrollingInterestForDomesticAndForeignOperationsDetail" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments_19dfad62-5a43-dcc4-04a8-012732c1ed97" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic_e6f9d43e-fcd6-745d-b634-9ed4792095b2" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments_19dfad62-5a43-dcc4-04a8-012732c1ed97" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic_e6f9d43e-fcd6-745d-b634-9ed4792095b2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign_a4e74316-f31b-80bc-a44a-3464e9dcdb33" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments_19dfad62-5a43-dcc4-04a8-012732c1ed97" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign_a4e74316-f31b-80bc-a44a-3464e9dcdb33" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/IncomeTaxesSummaryOfIncomeBeforeTaxesForContinuingAndDiscontinuedOperationsDetail" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeLossIncludingPortionAttributableToNoncontrollingInterest" xlink:label="loc_us-gaap_IncomeLossIncludingPortionAttributableToNoncontrollingInterest_711a0342-c23b-0a89-bf1c-dd2cb254a4a5" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_4d8b6d19-6a54-06aa-2077-c10380bd20d1" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeLossIncludingPortionAttributableToNoncontrollingInterest_711a0342-c23b-0a89-bf1c-dd2cb254a4a5" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_4d8b6d19-6a54-06aa-2077-c10380bd20d1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DiscontinuedOperationIncomeLossFromDiscontinuedOperationBeforeIncomeTax" xlink:label="loc_us-gaap_DiscontinuedOperationIncomeLossFromDiscontinuedOperationBeforeIncomeTax_e6c2b52f-6843-2914-0fae-f74995d125a1" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeLossIncludingPortionAttributableToNoncontrollingInterest_711a0342-c23b-0a89-bf1c-dd2cb254a4a5" xlink:to="loc_us-gaap_DiscontinuedOperationIncomeLossFromDiscontinuedOperationBeforeIncomeTax_e6c2b52f-6843-2914-0fae-f74995d125a1" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/IncomeTaxesSummaryOfIncomeTaxExpenseBenefitDetail" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeTaxExpenseBenefitIntraperiodTaxAllocation" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefitIntraperiodTaxAllocation_5ec605a5-eab5-76d6-a1b9-0aee50e22811" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeTaxExpenseBenefit" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_97bbae57-7f84-4da9-acab-610e56204929" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefitIntraperiodTaxAllocation_5ec605a5-eab5-76d6-a1b9-0aee50e22811" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_97bbae57-7f84-4da9-acab-610e56204929" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CurrentIncomeTaxExpenseBenefit" xlink:label="loc_us-gaap_CurrentIncomeTaxExpenseBenefit_816edbc5-9d4b-113c-7ce2-6c08dd555314" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefit_97bbae57-7f84-4da9-acab-610e56204929" xlink:to="loc_us-gaap_CurrentIncomeTaxExpenseBenefit_816edbc5-9d4b-113c-7ce2-6c08dd555314" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CurrentFederalTaxExpenseBenefit" xlink:label="loc_us-gaap_CurrentFederalTaxExpenseBenefit_b975ff9b-a11f-f2b5-e104-e0266dbbbfc6" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CurrentIncomeTaxExpenseBenefit_816edbc5-9d4b-113c-7ce2-6c08dd555314" xlink:to="loc_us-gaap_CurrentFederalTaxExpenseBenefit_b975ff9b-a11f-f2b5-e104-e0266dbbbfc6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CurrentStateAndLocalTaxExpenseBenefit" xlink:label="loc_us-gaap_CurrentStateAndLocalTaxExpenseBenefit_4d365c95-da3d-c3cb-6f6b-7945d285af9f" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CurrentIncomeTaxExpenseBenefit_816edbc5-9d4b-113c-7ce2-6c08dd555314" xlink:to="loc_us-gaap_CurrentStateAndLocalTaxExpenseBenefit_4d365c95-da3d-c3cb-6f6b-7945d285af9f" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CurrentForeignTaxExpenseBenefit" xlink:label="loc_us-gaap_CurrentForeignTaxExpenseBenefit_bbb5a6cc-fe5e-18f1-e9f0-76884d58b714" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CurrentIncomeTaxExpenseBenefit_816edbc5-9d4b-113c-7ce2-6c08dd555314" xlink:to="loc_us-gaap_CurrentForeignTaxExpenseBenefit_bbb5a6cc-fe5e-18f1-e9f0-76884d58b714" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredIncomeTaxExpenseBenefit" xlink:label="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_e8a9abf2-38d3-77d1-fb6b-693fef632294" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefit_97bbae57-7f84-4da9-acab-610e56204929" xlink:to="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_e8a9abf2-38d3-77d1-fb6b-693fef632294" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredFederalIncomeTaxExpenseBenefit" xlink:label="loc_us-gaap_DeferredFederalIncomeTaxExpenseBenefit_650e6c8f-1409-4de1-126f-784909f82e64" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_e8a9abf2-38d3-77d1-fb6b-693fef632294" xlink:to="loc_us-gaap_DeferredFederalIncomeTaxExpenseBenefit_650e6c8f-1409-4de1-126f-784909f82e64" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredStateAndLocalIncomeTaxExpenseBenefit" xlink:label="loc_us-gaap_DeferredStateAndLocalIncomeTaxExpenseBenefit_10aa09ac-60b4-bd88-6c3b-c85b3f0fbf0a" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_e8a9abf2-38d3-77d1-fb6b-693fef632294" xlink:to="loc_us-gaap_DeferredStateAndLocalIncomeTaxExpenseBenefit_10aa09ac-60b4-bd88-6c3b-c85b3f0fbf0a" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredForeignIncomeTaxExpenseBenefit" xlink:label="loc_us-gaap_DeferredForeignIncomeTaxExpenseBenefit_840ca4a2-1542-fad2-992c-40136594b396" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_e8a9abf2-38d3-77d1-fb6b-693fef632294" xlink:to="loc_us-gaap_DeferredForeignIncomeTaxExpenseBenefit_840ca4a2-1542-fad2-992c-40136594b396" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DiscontinuedOperationTaxEffectOfDiscontinuedOperation" xlink:label="loc_us-gaap_DiscontinuedOperationTaxEffectOfDiscontinuedOperation_925a043d-18b3-5d03-8e0b-c0fb4146cd8c" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeTaxExpenseBenefitIntraperiodTaxAllocation_5ec605a5-eab5-76d6-a1b9-0aee50e22811" xlink:to="loc_us-gaap_DiscontinuedOperationTaxEffectOfDiscontinuedOperation_925a043d-18b3-5d03-8e0b-c0fb4146cd8c" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/IncomeTaxesTables" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/LongTermDebt" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/LongTermDebtEstimatedMaturitiesOfLongTermDebtDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/LongTermDebtNarrativeDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/LongTermDebtScheduleOfCarryingAmountsAndEstimatedFairValuesOfLongTermDebtDetail" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LongTermDebt" xlink:label="loc_us-gaap_LongTermDebt_80dca0ba-44dc-8565-fb9b-c2edfc8c357d" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LongTermDebtCurrent" xlink:label="loc_us-gaap_LongTermDebtCurrent_0d8925ae-714a-26e4-aa69-2d9eac65a5c6" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LongTermDebt_80dca0ba-44dc-8565-fb9b-c2edfc8c357d" xlink:to="loc_us-gaap_LongTermDebtCurrent_0d8925ae-714a-26e4-aa69-2d9eac65a5c6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LongTermDebtNoncurrent" xlink:label="loc_us-gaap_LongTermDebtNoncurrent_fcfc6b17-bfc5-2ebc-3fc1-751aa446a572" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LongTermDebt_80dca0ba-44dc-8565-fb9b-c2edfc8c357d" xlink:to="loc_us-gaap_LongTermDebtNoncurrent_fcfc6b17-bfc5-2ebc-3fc1-751aa446a572" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_UnsecuredDebt" xlink:label="loc_us-gaap_UnsecuredDebt_fdc9d00d-e162-6828-9393-ab3548a11f46" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LongTermDebtNoncurrent_fcfc6b17-bfc5-2ebc-3fc1-751aa446a572" xlink:to="loc_us-gaap_UnsecuredDebt_fdc9d00d-e162-6828-9393-ab3548a11f46" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LineOfCredit" xlink:label="loc_us-gaap_LineOfCredit_65fb8a1f-903e-a726-6d94-3932acece0b3" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LongTermDebtNoncurrent_fcfc6b17-bfc5-2ebc-3fc1-751aa446a572" xlink:to="loc_us-gaap_LineOfCredit_65fb8a1f-903e-a726-6d94-3932acece0b3" xlink:type="arc" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LongTermDebtNoncurrent_fcfc6b17-bfc5-2ebc-3fc1-751aa446a572" xlink:to="loc_us-gaap_LongTermDebtCurrent_0d8925ae-714a-26e4-aa69-2d9eac65a5c6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SecuredDebt" xlink:label="loc_us-gaap_SecuredDebt_07f69f5d-1693-d29d-ef9d-db0691482fe5" xlink:type="locator" />
    <link:calculationArc order="4" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LongTermDebtNoncurrent_fcfc6b17-bfc5-2ebc-3fc1-751aa446a572" xlink:to="loc_us-gaap_SecuredDebt_07f69f5d-1693-d29d-ef9d-db0691482fe5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherLongTermDebt" xlink:label="loc_us-gaap_OtherLongTermDebt_2822e451-0377-c062-4be6-063b9110832b" xlink:type="locator" />
    <link:calculationArc order="5" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LongTermDebtNoncurrent_fcfc6b17-bfc5-2ebc-3fc1-751aa446a572" xlink:to="loc_us-gaap_OtherLongTermDebt_2822e451-0377-c062-4be6-063b9110832b" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/LongTermDebtSummaryOfEffectiveInterestRatesOnVariableRateIdrbsDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/LongTermDebtTables" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/OtherComprehensiveIncomeAndAccumulatedOtherComprehensiveIncomeAoci" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/OtherComprehensiveIncomeAndAccumulatedOtherComprehensiveIncomeAociAmountRecognizedBeforeIncomeTaxAssociatedWithDefinedBenefitPlansInAccumulatedOtherComprehensiveIncomeDetail" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTax" xlink:label="loc_us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTax_0f27487e-3d5a-f377-0098-b0e848cdad0f" xlink:type="locator" />
    <link:loc xlink:href="swx-20181231.xsd#swx_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeLossAmountRecognizedRegulatoryAssetsBeforeTax" xlink:label="loc_swx_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeLossAmountRecognizedRegulatoryAssetsBeforeTax_3F1B5288F95F2041B4E2B0D67140E01E" xlink:type="locator" />
    <link:calculationArc order="1" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTax_0f27487e-3d5a-f377-0098-b0e848cdad0f" xlink:to="loc_swx_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeLossAmountRecognizedRegulatoryAssetsBeforeTax_3F1B5288F95F2041B4E2B0D67140E01E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetGainsLossesBeforeTax" xlink:label="loc_us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetGainsLossesBeforeTax_489d8e73-cdae-5246-456e-868aff0fc625" xlink:type="locator" />
    <link:calculationArc order="2" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTax_0f27487e-3d5a-f377-0098-b0e848cdad0f" xlink:to="loc_us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetGainsLossesBeforeTax_489d8e73-cdae-5246-456e-868aff0fc625" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetPriorServiceCostCreditBeforeTax" xlink:label="loc_us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetPriorServiceCostCreditBeforeTax_5cad856d-5bc0-8a6d-8833-76680f9c72f2" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTax_0f27487e-3d5a-f377-0098-b0e848cdad0f" xlink:to="loc_us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetPriorServiceCostCreditBeforeTax_5cad856d-5bc0-8a6d-8833-76680f9c72f2" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/OtherComprehensiveIncomeAndAccumulatedOtherComprehensiveIncomeAociAociRollforwardDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_e68ce304-18e4-96c0-3260-363a872863db" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTax_fd048371-7ae9-878a-d401-982ff73ca2e8" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_e68ce304-18e4-96c0-3260-363a872863db" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTax_fd048371-7ae9-878a-d401-982ff73ca2e8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossTax_aa6d7695-3c9c-a820-1c3c-0e977db4a781" xlink:type="locator" />
    <link:calculationArc order="2" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_e68ce304-18e4-96c0-3260-363a872863db" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossTax_aa6d7695-3c9c-a820-1c3c-0e977db4a781" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StockholdersEquity" xlink:label="loc_us-gaap_StockholdersEquity_6765f135-8c69-bebc-a116-d59a52a5b2f2" xlink:type="locator" />
    <link:loc xlink:href="swx-20181231.xsd#swx_StockholdersEquityAttributableToParentBeforeTax" xlink:label="loc_swx_StockholdersEquityAttributableToParentBeforeTax_890524532090CAA07459E5B1BBC7C203" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_6765f135-8c69-bebc-a116-d59a52a5b2f2" xlink:to="loc_swx_StockholdersEquityAttributableToParentBeforeTax_890524532090CAA07459E5B1BBC7C203" xlink:type="arc" />
    <link:loc xlink:href="swx-20181231.xsd#swx_StockholdersEquityAttributableToParentTax" xlink:label="loc_swx_StockholdersEquityAttributableToParentTax_34AEEFBC11CC273870EAE5B24F71A00E" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_6765f135-8c69-bebc-a116-d59a52a5b2f2" xlink:to="loc_swx_StockholdersEquityAttributableToParentTax_34AEEFBC11CC273870EAE5B24F71A00E" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/OtherComprehensiveIncomeAndAccumulatedOtherComprehensiveIncomeAociNarrativeDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/OtherComprehensiveIncomeAndAccumulatedOtherComprehensiveIncomeAociRelatedTaxEffectsAllocatedToOciDetail" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax_3d99831a-ebd4-5b79-0782-1b1eabd6a9c8" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax_3abb3548-5c4d-f7e9-ec84-657c5af7d43a" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax_3d99831a-ebd4-5b79-0782-1b1eabd6a9c8" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax_3abb3548-5c4d-f7e9-ec84-657c5af7d43a" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsTax_a61429d7-b03e-55db-d324-cd80005c65f9" xlink:type="locator" />
    <link:calculationArc order="2" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax_3d99831a-ebd4-5b79-0782-1b1eabd6a9c8" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsTax_a61429d7-b03e-55db-d324-cd80005c65f9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax" xlink:label="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_370db1e9-72b2-d2e9-181c-90ae6fba7f8b" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax" xlink:label="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax_19a9882d-ffc5-f60a-48da-a57a1ebf19e9" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_370db1e9-72b2-d2e9-181c-90ae6fba7f8b" xlink:to="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax_19a9882d-ffc5-f60a-48da-a57a1ebf19e9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ReclassificationFromAociCurrentPeriodTax" xlink:label="loc_us-gaap_ReclassificationFromAociCurrentPeriodTax_41fedcfc-16d1-4fa1-3e6c-cadfee11fe94" xlink:type="locator" />
    <link:calculationArc order="2" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_370db1e9-72b2-d2e9-181c-90ae6fba7f8b" xlink:to="loc_us-gaap_ReclassificationFromAociCurrentPeriodTax_41fedcfc-16d1-4fa1-3e6c-cadfee11fe94" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossTax_aa6d7695-3c9c-a820-1c3c-0e977db4a781" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossTax_aa6d7695-3c9c-a820-1c3c-0e977db4a781" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsTax_a61429d7-b03e-55db-d324-cd80005c65f9" xlink:type="arc" />
    <link:calculationArc order="2" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossTax_aa6d7695-3c9c-a820-1c3c-0e977db4a781" xlink:to="loc_us-gaap_ReclassificationFromAociCurrentPeriodTax_41fedcfc-16d1-4fa1-3e6c-cadfee11fe94" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTax_fd048371-7ae9-878a-d401-982ff73ca2e8" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTax_fd048371-7ae9-878a-d401-982ff73ca2e8" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax_3abb3548-5c4d-f7e9-ec84-657c5af7d43a" xlink:type="arc" />
    <link:calculationArc order="2" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTax_fd048371-7ae9-878a-d401-982ff73ca2e8" xlink:to="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax_19a9882d-ffc5-f60a-48da-a57a1ebf19e9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_e68ce304-18e4-96c0-3260-363a872863db" xlink:type="locator" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/OtherComprehensiveIncomeAndAccumulatedOtherComprehensiveIncomeAociScheduleOfEstimatedAmountsAmortizedFromAccumulatedOtherComprehensiveIncomeOrRegulatoryAssetsIntoNetPeriodicBenefitCostDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/OtherComprehensiveIncomeAndAccumulatedOtherComprehensiveIncomeAociTables" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/PensionAndOtherPostretirementBenefits" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/PensionAndOtherPostretirementBenefitsCostOfRetirementPlanDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/PensionAndOtherPostretirementBenefitsNarrativeDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/PensionAndOtherPostretirementBenefitsScheduleOfAccumulatedBenefitObligationDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/PensionAndOtherPostretirementBenefitsScheduleOfAmountsRecognizedInBalanceSheetAndIncomeStatementDetail" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DefinedBenefitPlanFundedStatusOfPlan" xlink:label="loc_us-gaap_DefinedBenefitPlanFundedStatusOfPlan_6756bfa8-d44d-11e3-e639-2c0d1784c09a" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DefinedBenefitPlanBenefitObligation" xlink:label="loc_us-gaap_DefinedBenefitPlanBenefitObligation_4a6a9edc-7d09-7c7e-e64b-45faecd35930" xlink:type="locator" />
    <link:calculationArc order="1" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DefinedBenefitPlanFundedStatusOfPlan_6756bfa8-d44d-11e3-e639-2c0d1784c09a" xlink:to="loc_us-gaap_DefinedBenefitPlanBenefitObligation_4a6a9edc-7d09-7c7e-e64b-45faecd35930" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DefinedBenefitPlanFairValueOfPlanAssets" xlink:label="loc_us-gaap_DefinedBenefitPlanFairValueOfPlanAssets_166d727c-5242-f06b-d573-7921ffbf75e2" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DefinedBenefitPlanFundedStatusOfPlan_6756bfa8-d44d-11e3-e639-2c0d1784c09a" xlink:to="loc_us-gaap_DefinedBenefitPlanFairValueOfPlanAssets_166d727c-5242-f06b-d573-7921ffbf75e2" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/PensionAndOtherPostretirementBenefitsScheduleOfAssumptionsUsedDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/PensionAndOtherPostretirementBenefitsScheduleOfExpectedBenefitPaymentsDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/PensionAndOtherPostretirementBenefitsScheduleOfFairValueOfPlanAssetsDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/PensionAndOtherPostretirementBenefitsScheduleOfNetPeriodicBenefitCostAndWeightedAverageAssumptionsDetail" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost" xlink:label="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost_f8c4af80-3396-31ad-927b-214035fcad4c" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DefinedBenefitPlanServiceCost" xlink:label="loc_us-gaap_DefinedBenefitPlanServiceCost_50c65441-5a4a-7b70-8a6f-4bdf84901dd7" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost_f8c4af80-3396-31ad-927b-214035fcad4c" xlink:to="loc_us-gaap_DefinedBenefitPlanServiceCost_50c65441-5a4a-7b70-8a6f-4bdf84901dd7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DefinedBenefitPlanInterestCost" xlink:label="loc_us-gaap_DefinedBenefitPlanInterestCost_cc5d4539-1440-3488-daaf-595604d399d2" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost_f8c4af80-3396-31ad-927b-214035fcad4c" xlink:to="loc_us-gaap_DefinedBenefitPlanInterestCost_cc5d4539-1440-3488-daaf-595604d399d2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets" xlink:label="loc_us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets_9eb8402e-17f1-615b-f0e0-f772c38d36ef" xlink:type="locator" />
    <link:calculationArc order="3" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost_f8c4af80-3396-31ad-927b-214035fcad4c" xlink:to="loc_us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets_9eb8402e-17f1-615b-f0e0-f772c38d36ef" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit" xlink:label="loc_us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit_ec71b0cf-49f0-3a78-6e16-666ec068d28b" xlink:type="locator" />
    <link:calculationArc order="4" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost_f8c4af80-3396-31ad-927b-214035fcad4c" xlink:to="loc_us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit_ec71b0cf-49f0-3a78-6e16-666ec068d28b" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DefinedBenefitPlanAmortizationOfGainsLosses" xlink:label="loc_us-gaap_DefinedBenefitPlanAmortizationOfGainsLosses_238da213-7798-05e5-0178-b455f068fdf8" xlink:type="locator" />
    <link:calculationArc order="5" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost_f8c4af80-3396-31ad-927b-214035fcad4c" xlink:to="loc_us-gaap_DefinedBenefitPlanAmortizationOfGainsLosses_238da213-7798-05e5-0178-b455f068fdf8" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/PensionAndOtherPostretirementBenefitsScheduleOfNewAccountingPronouncementsDetails" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/PensionAndOtherPostretirementBenefitsScheduleOfOtherChangesInPlanAssetsAndBenefitObligationsRecognizedInNetPeriodicBenefitCostAndOtherComprehensiveIncomeDetail" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AmountRecognizedInNetPeriodicBenefitCostAndOtherComprehensiveIncomeLossBeforeTax" xlink:label="loc_us-gaap_AmountRecognizedInNetPeriodicBenefitCostAndOtherComprehensiveIncomeLossBeforeTax_b5e1f6cc-3c19-f5fb-07ff-bafcf832192e" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DefinedBenefitPlanAmountsRecognizedInOtherComprehensiveIncomeLossNetGainLossBeforeTax" xlink:label="loc_us-gaap_DefinedBenefitPlanAmountsRecognizedInOtherComprehensiveIncomeLossNetGainLossBeforeTax_75eccc4f-9ac0-4e30-f908-41fe09a26088" xlink:type="locator" />
    <link:calculationArc order="1" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AmountRecognizedInNetPeriodicBenefitCostAndOtherComprehensiveIncomeLossBeforeTax_b5e1f6cc-3c19-f5fb-07ff-bafcf832192e" xlink:to="loc_us-gaap_DefinedBenefitPlanAmountsRecognizedInOtherComprehensiveIncomeLossNetGainLossBeforeTax_75eccc4f-9ac0-4e30-f908-41fe09a26088" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansNetUnamortizedGainLossArisingDuringPeriodBeforeTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansNetUnamortizedGainLossArisingDuringPeriodBeforeTax_7a6b3159-85c2-3cb7-35ae-a023bdf89f97" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DefinedBenefitPlanAmountsRecognizedInOtherComprehensiveIncomeLossNetGainLossBeforeTax_75eccc4f-9ac0-4e30-f908-41fe09a26088" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansNetUnamortizedGainLossArisingDuringPeriodBeforeTax_7a6b3159-85c2-3cb7-35ae-a023bdf89f97" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditBeforeTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditBeforeTax_5a6927f8-c962-c8c0-1e84-0cb09af136b4" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DefinedBenefitPlanAmountsRecognizedInOtherComprehensiveIncomeLossNetGainLossBeforeTax_75eccc4f-9ac0-4e30-f908-41fe09a26088" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditBeforeTax_5a6927f8-c962-c8c0-1e84-0cb09af136b4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax_95aef994-7a6a-9ba8-df38-1ad015d6c8d2" xlink:type="locator" />
    <link:calculationArc order="3" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DefinedBenefitPlanAmountsRecognizedInOtherComprehensiveIncomeLossNetGainLossBeforeTax_75eccc4f-9ac0-4e30-f908-41fe09a26088" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax_95aef994-7a6a-9ba8-df38-1ad015d6c8d2" xlink:type="arc" />
    <link:loc xlink:href="swx-20181231.xsd#swx_DefinedBenefitPlanRegulatoryAdjustmentBeforeTax" xlink:label="loc_swx_DefinedBenefitPlanRegulatoryAdjustmentBeforeTax_bdb83bfb-9ea3-4f97-a77e-0e712b84f2d8" xlink:type="locator" />
    <link:calculationArc order="4" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DefinedBenefitPlanAmountsRecognizedInOtherComprehensiveIncomeLossNetGainLossBeforeTax_75eccc4f-9ac0-4e30-f908-41fe09a26088" xlink:to="loc_swx_DefinedBenefitPlanRegulatoryAdjustmentBeforeTax_bdb83bfb-9ea3-4f97-a77e-0e712b84f2d8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost" xlink:label="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost_f8c4af80-3396-31ad-927b-214035fcad4c" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AmountRecognizedInNetPeriodicBenefitCostAndOtherComprehensiveIncomeLossBeforeTax_b5e1f6cc-3c19-f5fb-07ff-bafcf832192e" xlink:to="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost_f8c4af80-3396-31ad-927b-214035fcad4c" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/PensionAndOtherPostretirementBenefitsTables" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/QuarterlyFinancialDataUnaudited" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/QuarterlyFinancialDataUnauditedDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/QuarterlyFinancialDataUnauditedTables" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/ReceivablesAndRelatedAllowances" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/ReceivablesAndRelatedAllowancesAdditionalInformationDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/ReceivablesAndRelatedAllowancesScheduleOfAccountsReceivableDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/ReceivablesAndRelatedAllowancesScheduleOfAllowanceForUncollectiblesDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/ReceivablesAndRelatedAllowancesScheduleOfPercentOfCustomersByStateDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/ReceivablesAndRelatedAllowancesTables" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/RegulatoryAssetsAndLiabilities" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/RegulatoryAssetsAndLiabilitiesScheduleOfComponentsOfOtherRegulatoryAssetsDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/RegulatoryAssetsAndLiabilitiesScheduleOfComponentsOfOtherRegulatoryLiabilitiesDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/RegulatoryAssetsAndLiabilitiesScheduleOfRegulatoryAssetsAndLiabilitiesDetail" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NetRegulatoryAssets" xlink:label="loc_us-gaap_NetRegulatoryAssets_e8f982a2-0436-2eb0-9502-f72b2f53ec35" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RegulatoryAssets" xlink:label="loc_us-gaap_RegulatoryAssets_d72dcccc-a153-58ff-9c60-c1d63f893a89" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetRegulatoryAssets_e8f982a2-0436-2eb0-9502-f72b2f53ec35" xlink:to="loc_us-gaap_RegulatoryAssets_d72dcccc-a153-58ff-9c60-c1d63f893a89" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RegulatoryLiabilities" xlink:label="loc_us-gaap_RegulatoryLiabilities_5b3db3e5-0f26-a9a9-7f51-274dff9b9387" xlink:type="locator" />
    <link:calculationArc order="2" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetRegulatoryAssets_e8f982a2-0436-2eb0-9502-f72b2f53ec35" xlink:to="loc_us-gaap_RegulatoryLiabilities_5b3db3e5-0f26-a9a9-7f51-274dff9b9387" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/RegulatoryAssetsAndLiabilitiesTables" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/ReorganizationImpactsDiscontinuedOperationsSolelyRelatedToSouthwestGasCorporation" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/ReorganizationImpactsDiscontinuedOperationsSolelyRelatedToSouthwestGasCorporationDetail" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DiscontinuedOperationIncomeLossFromDiscontinuedOperationBeforeIncomeTax" xlink:label="loc_us-gaap_DiscontinuedOperationIncomeLossFromDiscontinuedOperationBeforeIncomeTax_e6c2b52f-6843-2914-0fae-f74995d125a1" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationOperatingIncomeLoss" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationOperatingIncomeLoss_907297cd-d532-8c4f-862e-e64a6cc6758b" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DiscontinuedOperationIncomeLossFromDiscontinuedOperationBeforeIncomeTax_e6c2b52f-6843-2914-0fae-f74995d125a1" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationOperatingIncomeLoss_907297cd-d532-8c4f-862e-e64a6cc6758b" xlink:type="arc" />
    <link:loc xlink:href="swx-20181231.xsd#swx_DisposalGroupIncludingDiscontinuedOperationConstructionRevenues" xlink:label="loc_swx_DisposalGroupIncludingDiscontinuedOperationConstructionRevenues_d61fed35-ef18-4a56-1fb4-0e712b84531c" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationOperatingIncomeLoss_907297cd-d532-8c4f-862e-e64a6cc6758b" xlink:to="loc_swx_DisposalGroupIncludingDiscontinuedOperationConstructionRevenues_d61fed35-ef18-4a56-1fb4-0e712b84531c" xlink:type="arc" />
    <link:loc xlink:href="swx-20181231.xsd#swx_DisposalGroupIncludingDiscontinuedOperationConstructionExpenses" xlink:label="loc_swx_DisposalGroupIncludingDiscontinuedOperationConstructionExpenses_8b2fd6d2-008a-17e5-abd3-0e712b8b3955" xlink:type="locator" />
    <link:calculationArc order="2" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationOperatingIncomeLoss_907297cd-d532-8c4f-862e-e64a6cc6758b" xlink:to="loc_swx_DisposalGroupIncludingDiscontinuedOperationConstructionExpenses_8b2fd6d2-008a-17e5-abd3-0e712b8b3955" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DepreciationAndAmortizationDiscontinuedOperations" xlink:label="loc_us-gaap_DepreciationAndAmortizationDiscontinuedOperations_28fd10b9-9afe-984a-d86f-f32038cbb989" xlink:type="locator" />
    <link:calculationArc order="3" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationOperatingIncomeLoss_907297cd-d532-8c4f-862e-e64a6cc6758b" xlink:to="loc_us-gaap_DepreciationAndAmortizationDiscontinuedOperations_28fd10b9-9afe-984a-d86f-f32038cbb989" xlink:type="arc" />
    <link:loc xlink:href="swx-20181231.xsd#swx_DisposalGroupIncludingDiscontinuedOperationOtherIncomeExpense" xlink:label="loc_swx_DisposalGroupIncludingDiscontinuedOperationOtherIncomeExpense_205aa4a4-6133-3e0d-8015-0e712b814239" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DiscontinuedOperationIncomeLossFromDiscontinuedOperationBeforeIncomeTax_e6c2b52f-6843-2914-0fae-f74995d125a1" xlink:to="loc_swx_DisposalGroupIncludingDiscontinuedOperationOtherIncomeExpense_205aa4a4-6133-3e0d-8015-0e712b814239" xlink:type="arc" />
    <link:loc xlink:href="swx-20181231.xsd#swx_DisposalGroupIncludingDiscontinuedOperationInterestIncomeExpenseNet" xlink:label="loc_swx_DisposalGroupIncludingDiscontinuedOperationInterestIncomeExpenseNet_ac347f15-e64a-38fa-4b29-0e712b7a6465" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_DiscontinuedOperationIncomeLossFromDiscontinuedOperationBeforeIncomeTax_e6c2b52f-6843-2914-0fae-f74995d125a1" xlink:to="loc_swx_DisposalGroupIncludingDiscontinuedOperationInterestIncomeExpenseNet_ac347f15-e64a-38fa-4b29-0e712b7a6465" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/ReorganizationImpactsDiscontinuedOperationsSolelyRelatedToSouthwestGasCorporationTables" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/Revenue" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/RevenueNarrativeDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/RevenueRevenuePerformanceObligationDetails" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/RevenueScheduleOfGasOperatingRevenueDetail" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RegulatedOperatingRevenueGas" xlink:label="loc_us-gaap_RegulatedOperatingRevenueGas_b175b957-2266-28b0-f418-63a2a0f1cb17" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_1c604cfe-da19-5194-72b6-98be0130cfb7" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_RegulatedOperatingRevenueGas_b175b957-2266-28b0-f418-63a2a0f1cb17" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_1c604cfe-da19-5194-72b6-98be0130cfb7" xlink:type="arc" />
    <link:loc xlink:href="swx-20181231.xsd#swx_AlternativeRevenueProgramRevenuesDeferrals" xlink:label="loc_swx_AlternativeRevenueProgramRevenuesDeferrals_3306c617-4b87-9753-e007-0e712b8886fb" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_RegulatedOperatingRevenueGas_b175b957-2266-28b0-f418-63a2a0f1cb17" xlink:to="loc_swx_AlternativeRevenueProgramRevenuesDeferrals_3306c617-4b87-9753-e007-0e712b8886fb" xlink:type="arc" />
    <link:loc xlink:href="swx-20181231.xsd#swx_OtherRevenue" xlink:label="loc_swx_OtherRevenue_1a972a0b-b675-fd67-de77-0e712b7e3c46" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_RegulatedOperatingRevenueGas_b175b957-2266-28b0-f418-63a2a0f1cb17" xlink:to="loc_swx_OtherRevenue_1a972a0b-b675-fd67-de77-0e712b7e3c46" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/RevenueScheduleOfUtilityInfrastructureServicesContractsReceivableDetail" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AccountsReceivableNet" xlink:label="loc_us-gaap_AccountsReceivableNet_76017261-aa07-deb3-a119-3ccb7898c700" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AccountsReceivableGross" xlink:label="loc_us-gaap_AccountsReceivableGross_fa3bae7b-e6bf-6258-8d6f-eb7d0a0db005" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AccountsReceivableNet_76017261-aa07-deb3-a119-3ccb7898c700" xlink:to="loc_us-gaap_AccountsReceivableGross_fa3bae7b-e6bf-6258-8d6f-eb7d0a0db005" xlink:type="arc" />
    <link:loc xlink:href="swx-20181231.xsd#swx_BilledOnCompletedContractsAndContractsInProgress" xlink:label="loc_swx_BilledOnCompletedContractsAndContractsInProgress_a47d3124-d71a-c533-7b3f-0e712b87aaaa" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AccountsReceivableGross_fa3bae7b-e6bf-6258-8d6f-eb7d0a0db005" xlink:to="loc_swx_BilledOnCompletedContractsAndContractsInProgress_a47d3124-d71a-c533-7b3f-0e712b87aaaa" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherReceivables" xlink:label="loc_us-gaap_OtherReceivables_66d33d39-750d-8c64-4fb6-6affdade8a19" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AccountsReceivableGross_fa3bae7b-e6bf-6258-8d6f-eb7d0a0db005" xlink:to="loc_us-gaap_OtherReceivables_66d33d39-750d-8c64-4fb6-6affdade8a19" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AllowanceForDoubtfulAccountsReceivable" xlink:label="loc_us-gaap_AllowanceForDoubtfulAccountsReceivable_4d5ed4c1-86d2-778a-ee35-20b59d9a388f" xlink:type="locator" />
    <link:calculationArc order="2" weight="-1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AccountsReceivableNet_76017261-aa07-deb3-a119-3ccb7898c700" xlink:to="loc_us-gaap_AllowanceForDoubtfulAccountsReceivable_4d5ed4c1-86d2-778a-ee35-20b59d9a388f" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/RevenueSummaryOfInformationAboutReceivablesDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/RevenueSummaryOfRevenueDisaggregatedByServiceTypeAndContractTypeDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/RevenueTables" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/SegmentInformation" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/SegmentInformationAccountsReceivableForServicesDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/SegmentInformationNarrativeDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/SegmentInformationScheduleOfRevenuesByGeographicAreaDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/SegmentInformationScheduleOfSegmentReportingInformationDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/SegmentInformationTables" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/ShareBasedCompensation" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/ShareBasedCompensationNarrativeDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/ShareBasedCompensationScheduleOfNonvestedPerformanceAndRestrictedStockUnitPlansDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/ShareBasedCompensationScheduleOfShareBasedPlanCompensationExpenseIncludingCashAwardDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/ShareBasedCompensationScheduleOfStockOptionsActivityDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/ShareBasedCompensationSummaryOfMarketPricesOfCommonStockDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/ShareBasedCompensationTables" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/ShortTermDebt" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/ShortTermDebtDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/UtilityInfrastructureServicesNoncontrollingInterests" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/UtilityInfrastructureServicesNoncontrollingInterestsAdditionalInformationDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/UtilityInfrastructureServicesNoncontrollingInterestsSummaryOfRedeemableNoncontrollingInterestDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/UtilityInfrastructureServicesNoncontrollingInterestsTables" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/UtilityPlantAndLeases" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/UtilityPlantAndLeasesNarrativeDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/UtilityPlantAndLeasesScheduleOfDepreciationAndAmortizationExpenseDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/UtilityPlantAndLeasesScheduleOfFutureMinimumLeasePaymentsForOperatingLeasesDetail" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDue" xlink:label="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDue_30d028f9-2f3a-4a0c-02f8-ea9552d875b6" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent" xlink:label="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent_f67237f3-7c78-8a5c-b7b3-17f1eb0b017a" xlink:type="locator" />
    <link:calculationArc order="1" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDue_30d028f9-2f3a-4a0c-02f8-ea9552d875b6" xlink:to="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent_f67237f3-7c78-8a5c-b7b3-17f1eb0b017a" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears" xlink:label="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears_ccaff3fc-3d87-e58a-0083-69dda0c10f9d" xlink:type="locator" />
    <link:calculationArc order="2" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDue_30d028f9-2f3a-4a0c-02f8-ea9552d875b6" xlink:to="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears_ccaff3fc-3d87-e58a-0083-69dda0c10f9d" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears" xlink:label="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears_39e76369-4fdc-9d5f-860a-45d0795e5fb0" xlink:type="locator" />
    <link:calculationArc order="3" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDue_30d028f9-2f3a-4a0c-02f8-ea9552d875b6" xlink:to="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears_39e76369-4fdc-9d5f-860a-45d0795e5fb0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears" xlink:label="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears_fe404cae-7fcc-3489-844f-4d90e9776180" xlink:type="locator" />
    <link:calculationArc order="4" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDue_30d028f9-2f3a-4a0c-02f8-ea9552d875b6" xlink:to="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears_fe404cae-7fcc-3489-844f-4d90e9776180" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFiveYears" xlink:label="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFiveYears_5b651b24-1278-4eab-c840-7002c6d68546" xlink:type="locator" />
    <link:calculationArc order="5" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDue_30d028f9-2f3a-4a0c-02f8-ea9552d875b6" xlink:to="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFiveYears_5b651b24-1278-4eab-c840-7002c6d68546" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueThereafter" xlink:label="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueThereafter_36c616b1-40de-90d4-3c05-7e224ce1169a" xlink:type="locator" />
    <link:calculationArc order="6" weight="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDue_30d028f9-2f3a-4a0c-02f8-ea9552d875b6" xlink:to="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueThereafter_36c616b1-40de-90d4-3c05-7e224ce1169a" xlink:type="arc" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/UtilityPlantAndLeasesScheduleOfNetUtilityPlantDetail" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PublicUtilitiesPropertyPlantAndEquipmentNet" xlink:label="loc_us-gaap_PublicUtilitiesPropertyPlantAndEquipmentNet_73987971-d446-86f2-6a5f-eb1fe277f208" xlink:type="locator" />
  </link:calculationLink>
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/UtilityPlantAndLeasesScheduleOfRentalPaymentsForOperatingLeasesDetail" xlink:type="extended" />
  <link:calculationLink xlink:role="http://www.southwestgas.com/role/UtilityPlantAndLeasesTables" xlink:type="extended" />
</link:linkbase>
