<?xml version="1.0" encoding="us-ascii"?>
<!--XBRL document created with Bowne Tagger. XBRL Parser version 10.0.0.34-->
<!--Based on XBRL 2.1-->
<!--Modified on: 8/5/2011 3:57:57 PM-->
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        <link:definition>0611 - Disclosure - Subsequent Events (Details)</link:definition>
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      <link:roleType roleURI="http://quantaservices.com/role/SubsequentEvents" id="SubsequentEvents">
        <link:definition>0211 - Disclosure - Subsequent Events</link:definition>
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        <link:definition>0606 - Disclosure - Debt Obligations (Details Textuals)</link:definition>
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        <link:definition>06081 - Disclosure - Long-term Incentive Plans (Details Textuals)</link:definition>
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        <link:definition>0508 - Disclosure - Long-term Incentive Plans (Tables)</link:definition>
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        <link:definition>0608 - Disclosure - Long-term Incentive Plans (Details)</link:definition>
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        <link:usedOn>link:calculationLink</link:usedOn>
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        <link:definition>06051 - Disclosure - Per Share Information (Details Textuals)</link:definition>
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        <link:usedOn>link:calculationLink</link:usedOn>
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        <link:definition>0208 - Disclosure - Long-term Incentive Plans</link:definition>
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        <link:definition>06101 - Disclosure - Segment Information (Details Textuals)</link:definition>
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        <link:definition>06091 - Disclosure - Commitments and Contingencies (Details Textuals)</link:definition>
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        <link:definition>06071 - Disclosure - Equity (Details Textuals)</link:definition>
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        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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      <link:roleType roleURI="http://quantaservices.com/role/GoodwillAndOtherIntangibleAssetsDetailsTextuals" id="GoodwillAndOtherIntangibleAssetsDetailsTextuals">
        <link:definition>06043 - Disclosure - Goodwill and Other Intangible Assets (Details Textuals)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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        <link:definition>06042 - Disclosure - Goodwill and Other Intangible Assets (Details 2)</link:definition>
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        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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        <link:definition>06041 - Disclosure - Goodwill and Other Intangible Assets (Details 1)</link:definition>
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        <link:usedOn>link:calculationLink</link:usedOn>
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        <link:definition>06021 - Disclosure - Summary of Significant Accounting Policies (DetailsTextuals)</link:definition>
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        <link:usedOn>link:calculationLink</link:usedOn>
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        <link:definition>0510 - Disclosure - Segment Information (Tables)</link:definition>
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        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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      <link:roleType roleURI="http://quantaservices.com/role/SegmentInformationDetails" id="SegmentInformationDetails">
        <link:definition>0610 - Disclosure - Segment Information (Details)</link:definition>
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        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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        <link:definition>0609 - Disclosure - Commitments and Contingencies (Details)</link:definition>
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        <link:definition>0509 - Disclosure - Commitments and Contingencies (Tables)</link:definition>
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      <link:roleType roleURI="http://quantaservices.com/role/DocumentAndEntityInformation" id="DocumentAndEntityInformation">
        <link:definition>00 - Document - Document and Entity Information</link:definition>
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      <link:roleType roleURI="http://quantaservices.com/role/EquityTables" id="EquityTables">
        <link:definition>0507 - Disclosure - Equity (Tables)</link:definition>
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        <link:usedOn>link:definitionLink</link:usedOn>
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        <link:definition>0607 - Disclosure - Equity (Details)</link:definition>
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        <link:usedOn>link:definitionLink</link:usedOn>
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      <link:roleType roleURI="http://quantaservices.com/role/PerShareInformationTables" id="PerShareInformationTables">
        <link:definition>0505 - Disclosure - Per Share Information (Tables)</link:definition>
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        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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      <link:roleType roleURI="http://quantaservices.com/role/PerShareInformationDetails" id="PerShareInformationDetails">
        <link:definition>0605 - Disclosure - Per Share Information (Details)</link:definition>
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        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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      <link:roleType roleURI="http://quantaservices.com/role/GoodwillAndOtherIntangibleAssetsDetails" id="GoodwillAndOtherIntangibleAssetsDetails">
        <link:definition>0604 - Disclosure - Goodwill and Other Intangible Assets (Details)</link:definition>
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        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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      <link:roleType roleURI="http://quantaservices.com/role/GoodwillAndOtherIntangibleAssetsTables" id="GoodwillAndOtherIntangibleAssetsTables">
        <link:definition>0504 - Disclosure - Goodwill and Other Intangible Assets (Tables)</link:definition>
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        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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        <link:definition>0402 - Disclosure - Summary of Significant Accounting Policies (Policies)</link:definition>
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      <link:roleType roleURI="http://quantaservices.com/role/SummaryOfSignificantAccountingPoliciesTables" id="SummaryOfSignificantAccountingPoliciesTables">
        <link:definition>0502 - Disclosure - Summary of Significant Accounting Policies (Tables)</link:definition>
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        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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      <link:roleType roleURI="http://quantaservices.com/role/SummaryOfSignificantAccountingPoliciesDetails" id="SummaryOfSignificantAccountingPoliciesDetails">
        <link:definition>0602 - Disclosure - Summary of Significant Accounting Policies (Details)</link:definition>
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        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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      <link:roleType roleURI="http://quantaservices.com/role/BusinessAndOrganizationDetails" id="BusinessAndOrganizationDetails">
        <link:definition>0601 - Disclosure - Business and Organization (Details)</link:definition>
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        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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      <link:roleType roleURI="http://quantaservices.com/role/StockholdersEquity" id="StockholdersEquity">
        <link:definition>0207 - Disclosure - Equity</link:definition>
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        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://quantaservices.com/role/DebtObligations" id="DebtObligations">
        <link:definition>0206 - Disclosure - Debt Obligations</link:definition>
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        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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      <link:roleType roleURI="http://quantaservices.com/role/ChangesInAccountingPrinciplesAndNewAccountingPronouncements" id="ChangesInAccountingPrinciplesAndNewAccountingPronouncements">
        <link:definition>0203 - Disclosure - New Accounting Pronouncements</link:definition>
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        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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      <link:roleType roleURI="http://quantaservices.com/role/SummaryOfSignificantAccountingPolicies" id="SummaryOfSignificantAccountingPolicies">
        <link:definition>0202 - Disclosure - Summary of Significant Accounting Policies</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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      <link:roleType roleURI="http://quantaservices.com/role/BalanceSheetsParenthetical" id="BalanceSheetsParenthetical">
        <link:definition>0111 - Statement - Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://quantaservices.com/role/CommitmentsAndContingencies" id="CommitmentsAndContingencies">
        <link:definition>0209 - Disclosure - Commitments and Contingencies</link:definition>
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        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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      <link:roleType roleURI="http://quantaservices.com/role/SegmentInformation" id="SegmentInformation">
        <link:definition>0210 - Disclosure - Segment Information</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://quantaservices.com/role/PerShareInformation" id="PerShareInformation">
        <link:definition>0205 - Disclosure - Per Share Information</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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      <link:roleType roleURI="http://quantaservices.com/role/GoodwillAndOtherIntangibleAssets" id="GoodwillAndOtherIntangibleAssets">
        <link:definition>0204 - Disclosure - Goodwill and Other Intangible Assets</link:definition>
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        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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      <link:roleType roleURI="http://quantaservices.com/role/BusinessAndOrganization" id="BusinessAndOrganization">
        <link:definition>0201 - Disclosure - Business and Organization</link:definition>
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        <link:usedOn>link:definitionLink</link:usedOn>
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        <link:definition>0130 - Statement - Condensed Consolidated Statements of Cash Flows (Unaudited)</link:definition>
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        <link:usedOn>link:calculationLink</link:usedOn>
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      <link:roleType roleURI="http://quantaservices.com/role/StatementsOfOperations" id="StatementsOfOperations">
        <link:definition>0120 - Statement - Condensed Consolidated Statements of Operations (Unaudited)</link:definition>
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        <link:definition>0110 - Statement - Condensed Consolidated Balance Sheets (Unaudited)</link:definition>
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  <element id="pwr_NaturalGasAndPipelineDivisionMember" name="NaturalGasAndPipelineDivisionMember" type="us-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_TelecommunicationsDivisionMember" name="TelecommunicationsDivisionMember" type="us-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_GoodwillAndOtherIntangibleAssetsTextualsAbstract" name="GoodwillAndOtherIntangibleAssetsTextualsAbstract" abstract="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
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  <element id="pwr_PerShareInformationDetailsAbstract" name="PerShareInformationDetailsAbstract" abstract="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_PerShareInformationTextualsAbstract" name="PerShareInformationTextualsAbstract" abstract="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_DebtObligationsDetailsAbstract" name="DebtObligationsDetailsAbstract" abstract="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_DebtObligationsTextualsAbstract" name="DebtObligationsTextualsAbstract" abstract="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
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  <element id="pwr_InterestRateInExcessOfBaseRateMaximum" name="InterestRateInExcessOfBaseRateMaximum" type="us-types:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_LetterOfCreditFeeMinimum" name="LetterOfCreditFeeMinimum" type="us-types:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_LetterOfCreditFeeMaximum" name="LetterOfCreditFeeMaximum" type="us-types:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_CommitmentFeeMinimum" name="CommitmentFeeMinimum" type="us-types:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_CommitmentFeeMaximum" name="CommitmentFeeMaximum" type="us-types:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_ReductionInCompanyMaximumFundedDebtAndMaximumSeniorDebtByAllCashAndCashEquivalentsInExcessOfAmount" name="ReductionInCompanyMaximumFundedDebtAndMaximumSeniorDebtByAllCashAndCashEquivalentsInExcessOfAmount" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" />
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  <element id="pwr_EquityTextualsAbstract" name="EquityTextualsAbstract" abstract="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_InterestRateInExcessOfEurodollarRateMinimum" name="InterestRateInExcessOfEurodollarRateMinimum" type="us-types:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_InterestRateInExcessOfEurodollarRateMaximum" name="InterestRateInExcessOfEurodollarRateMaximum" type="us-types:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
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  <element id="pwr_FutureAmortizationExpenseInThirdFullFiscalYear" name="FutureAmortizationExpenseInThirdFullFiscalYear" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" />
  <element id="pwr_FutureAmortizationExpenseInFifthFullFiscalYearAndThereafter" name="FutureAmortizationExpenseInFifthFullFiscalYearAndThereafter" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" />
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  <element id="pwr_ActualTaxBenefitExpenseFromVestedRestrictedStock" name="ActualTaxBenefitExpenseFromVestedRestrictedStock" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" />
  <element id="pwr_ActualTaxBenefitExpenseRelatedToStockBasedCompensationExpense" name="ActualTaxBenefitExpenseRelatedToStockBasedCompensationExpense" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" />
  <element id="pwr_CommitmentsAndContingenciesTablesAbstract" name="CommitmentsAndContingenciesTablesAbstract" abstract="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
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  <element id="pwr_CommitmentsAndContingenciesTextualsAbstract" name="CommitmentsAndContingenciesTextualsAbstract" abstract="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
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  <element id="pwr_WorkersCompensationInsuranceClaimsDeductible" name="WorkersCompensationInsuranceClaimsDeductible" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" />
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  <element id="pwr_EstimatedCostToCompleteBondedProjects" name="EstimatedCostToCompleteBondedProjects" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" />
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  <element id="pwr_SegmentInformationTextualsAbstract" name="SegmentInformationTextualsAbstract" abstract="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
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  <element id="pwr_NaturalGasAndPipelineSegmentMember" name="NaturalGasAndPipelineSegmentMember" type="us-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_TelecommunicationsSegmentMember" name="TelecommunicationsSegmentMember" type="us-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_FiberOpticLicensingSegmentMember" name="FiberOpticLicensingSegmentMember" type="us-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_CorporateAndNonAllocatedCostsMember" name="CorporateAndNonAllocatedCostsMember" type="us-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
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  <element id="pwr_AutoLiabilityInsuranceClaimsDeductible" name="AutoLiabilityInsuranceClaimsDeductible" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" />
  <element id="pwr_ExchangeableSharesOfSubsidiaryMember" name="ExchangeableSharesOfSubsidiaryMember" type="us-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_FiniteLivedIntangibleAssetsForeignCurrencyAdjustments" name="FiniteLivedIntangibleAssetsForeignCurrencyAdjustments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" />
  <element id="pwr_NumberOfSeriesFPreferredStockIssuedToVotingTrust" name="NumberOfSeriesFPreferredStockIssuedToVotingTrust" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
  <element id="pwr_LiabilitiesUnderRestrictedStockUnits" name="LiabilitiesUnderRestrictedStockUnits" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" />
  <element id="pwr_PaymentOfFireSuppressionCosts" name="PaymentOfFireSuppressionCosts" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" />
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  <element id="pwr_FutureAmortizationExpenseInSecondFullFiscalYear" name="FutureAmortizationExpenseInSecondFullFiscalYear" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" />
  <element id="pwr_FutureAmortizationExpenseInFourthFullFiscalYear" name="FutureAmortizationExpenseInFourthFullFiscalYear" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" />
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  <element id="pwr_InterimCondensedConsolidatedFinancialInformationPolicyTextBlock" name="InterimCondensedConsolidatedFinancialInformationPolicyTextBlock" type="us-types:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_NonCashPortionOfLossOnEarlyExtinguishmentOfDebt" name="NonCashPortionOfLossOnEarlyExtinguishmentOfDebt" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" />
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  <element id="pwr_LongTermIncentivePlansTablesAbstract" name="LongTermIncentivePlansTablesAbstract" abstract="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_LongTermIncentivePlansDetailsAbstract" name="LongTermIncentivePlansDetailsAbstract" abstract="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_LongTermIncentivePlansTextualsAbstract" name="LongTermIncentivePlansTextualsAbstract" abstract="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
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  <element id="pwr_UseOfEstimatesPolicyTextBlock" name="UseOfEstimatesPolicyTextBlock" type="us-types:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
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  <element id="pwr_ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock" name="ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock" type="us-types:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_ScheduleOfCompensationCostForShareBasedPaymentArrangementsAllocationOfShareBasedCompensationCostsByPlanTableTextBlock" name="ScheduleOfCompensationCostForShareBasedPaymentArrangementsAllocationOfShareBasedCompensationCostsByPlanTableTextBlock" type="us-types:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
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  <element id="pwr_GoodwillImpairedAccumulatedImpairmentLoss" name="GoodwillImpairedAccumulatedImpairmentLoss" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" />
  <element id="pwr_GoodwillTranslationAdjustments" name="GoodwillTranslationAdjustments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" />
  <element id="pwr_GoodwillPurchaseAccountingAdjustments" name="GoodwillPurchaseAccountingAdjustments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" />
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  <element id="pwr_BaseRateInExcessOfFederalFundsRate" name="BaseRateInExcessOfFederalFundsRate" type="us-types:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_CrossDefaultProvisions" name="CrossDefaultProvisions" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" />
  <element id="pwr_CommonStockAvailableForAwardsPursuantToPlan" name="CommonStockAvailableForAwardsPursuantToPlan" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
  <element id="pwr_OperatingLeasesFutureMinimumPaymentsDueRemainderOfCurrentYear" name="OperatingLeasesFutureMinimumPaymentsDueRemainderOfCurrentYear" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" />
  <element id="pwr_OperatingLeasesFutureMinimumPaymentsDueInFirstFullYear" name="OperatingLeasesFutureMinimumPaymentsDueInFirstFullYear" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" />
  <element id="pwr_OperatingLeasesFutureMinimumPaymentsDueInSecondFullYear" name="OperatingLeasesFutureMinimumPaymentsDueInSecondFullYear" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" />
  <element id="pwr_OperatingLeasesFutureMinimumPaymentsDueInThirdFullYear" name="OperatingLeasesFutureMinimumPaymentsDueInThirdFullYear" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" />
  <element id="pwr_HealthCareDeductible" name="HealthCareDeductible" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" />
  <element id="pwr_OperatingLeasesFutureMinimumPaymentsDueInFourthFullYear" name="OperatingLeasesFutureMinimumPaymentsDueInFourthFullYear" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" />
  <element id="pwr_NewAccountingPronouncementsNotYetAdoptedPolicyTextBlock" name="NewAccountingPronouncementsNotYetAdoptedPolicyTextBlock" type="us-types:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_RedemptionPriceAsPercentageOfPrincipalAmountOfConvertibleSubordinatedNotes" name="RedemptionPriceAsPercentageOfPrincipalAmountOfConvertibleSubordinatedNotes" type="us-types:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
  <element id="pwr_RestrictedStockUnitsRSUMember" name="RestrictedStockUnitsRSUMember" type="us-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_MinimumFutureLicensingRevenuesInFirstFullYear" name="MinimumFutureLicensingRevenuesInFirstFullYear" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" />
  <element id="pwr_MinimumFutureLicensingRevenuesInThirdFullYear" name="MinimumFutureLicensingRevenuesInThirdFullYear" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" />
  <element id="pwr_MinimumFutureLicensingRevenuesInSecondFullYear" name="MinimumFutureLicensingRevenuesInSecondFullYear" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" />
  <element id="pwr_MinimumFutureLicensingRevenuesInFourthFullYear" name="MinimumFutureLicensingRevenuesInFourthFullYear" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" />
  <element id="pwr_FutureAmortizationExpenseInFirstFullFiscalYear" name="FutureAmortizationExpenseInFirstFullFiscalYear" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" />
  <element id="pwr_TaxBenefitRelatedToStockBasedCompensationExpense" name="TaxBenefitRelatedToStockBasedCompensationExpense" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" />
  <element id="pwr_CompensationExpenseRelatedToRestrictedStockUnits" name="CompensationExpenseRelatedToRestrictedStockUnits" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" />
  <element id="pwr_LettersOfCreditOutstandingIssuedUnderArrangementsOtherThanCreditFacility" name="LettersOfCreditOutstandingIssuedUnderArrangementsOtherThanCreditFacility" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" />
  <element id="pwr_OperatingLeasesFutureMinimumPaymentsDueAfterFourthFullYearForInterimPeriodsOrAfterFiveFullYearsForYearEndReportingPeriods" name="OperatingLeasesFutureMinimumPaymentsDueAfterFourthFullYearForInterimPeriodsOrAfterFiveFullYearsForYearEndReportingPeriods" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" />
  <element id="pwr_NumberOfLawsuitsRelatedToWildfireLitigation" name="NumberOfLawsuitsRelatedToWildfireLitigation" type="xbrli:integerItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
  <element id="pwr_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriodMinimum" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriodMinimum" type="xbrli:durationItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriodMaximum" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriodMaximum" type="xbrli:durationItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_AdditionalBusinessAndOrganizationTextualsAbstract" name="AdditionalBusinessAndOrganizationTextualsAbstract" abstract="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_AdditionalLongTermIncentivePlansTextualsAbstract" name="AdditionalLongTermIncentivePlansTextualsAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_LettersOfCreditOutstandingAmountIssuedUnderAgreementsOtherThanCreditFacility" name="LettersOfCreditOutstandingAmountIssuedUnderAgreementsOtherThanCreditFacility" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" />
  <element id="pwr_CommonStockWithheldForSettlementOfEmployeeTaxLiabilitiesMember" name="CommonStockWithheldForSettlementOfEmployeeTaxLiabilitiesMember" type="us-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_CommonStockRepurchasedUnderRepurchasePlanMember" name="CommonStockRepurchasedUnderRepurchasePlanMember" type="us-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_EquityAdditionalTextualsAbstract" name="EquityAdditionalTextualsAbstract" abstract="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_NumberOfLimitedVoteCommonStockReclassifiedAndConvertedForCommonStock" name="NumberOfLimitedVoteCommonStockReclassifiedAndConvertedForCommonStock" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_NumberOfLimitedVoteCommonStockExchangedForCommonStock" name="NumberOfLimitedVoteCommonStockExchangedForCommonStock" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_AggregateAuthorizedAmountOfCommonStockToBeRepurchased" name="AggregateAuthorizedAmountOfCommonStockToBeRepurchased" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" />
  <element id="pwr_NumberOfCommonStockSharesIssuedOnReclassificationAndConversionOfLimitedVoteCommonStock" name="NumberOfCommonStockSharesIssuedOnReclassificationAndConversionOfLimitedVoteCommonStock" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_NumberOfCommonStockSharesIssuedOnExchangeOfLimitedVoteCommonStock" name="NumberOfCommonStockSharesIssuedOnExchangeOfLimitedVoteCommonStock" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_OutstandingPerformanceBonds" name="OutstandingPerformanceBonds" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" />
  <element id="pwr_NumberOfInsurersParticipatingUnderReservationOfRights" name="NumberOfInsurersParticipatingUnderReservationOfRights" type="xbrli:integerItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
  <element id="pwr_FiberOpticLicensingTermsMinimumInYears" name="FiberOpticLicensingTermsMinimumInYears" type="xbrli:durationItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_FiberOpticLicensingTermsMaximumInYears" name="FiberOpticLicensingTermsMaximumInYears" type="xbrli:durationItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_NumberOfSharesOfCommonStockReceivedForEachExchangeableShare" name="NumberOfSharesOfCommonStockReceivedForEachExchangeableShare" type="xbrli:integerItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_MinimumNumberOfSharesThatCanBeExchangedByExchangeableShareholdersUnlessTotalNumberOfRemainingExchangeableSharesRegisteredInNameOfHolderIsLess" name="MinimumNumberOfSharesThatCanBeExchangedByExchangeableShareholdersUnlessTotalNumberOfRemainingExchangeableSharesRegisteredInNameOfHolderIsLess" type="xbrli:integerItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_FractionOfVoteLimitedVoteCommonStockholdersWereAllowedOnAllMattersOtherThanElectionOfBoard" name="FractionOfVoteLimitedVoteCommonStockholdersWereAllowedOnAllMattersOtherThanElectionOfBoard" type="xbrli:decimalItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
  <element id="pwr_NumberOfCommonStockSharesReceivedForEachShareOfLimitedVoteCommonStockConverted" name="NumberOfCommonStockSharesReceivedForEachShareOfLimitedVoteCommonStockConverted" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_DamagesCausedToAcreageDueToWildfire" name="DamagesCausedToAcreageDueToWildfire" type="xbrli:integerItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_DamagesCausedToHomesAndStructuresDueToWildfire" name="DamagesCausedToHomesAndStructuresDueToWildfire" type="xbrli:integerItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_AllegedDeathsCausedByWildfire" name="AllegedDeathsCausedByWildfire" type="xbrli:integerItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_AllegedNumberOfPersonalInjuriesCausedByWildfire" name="AllegedNumberOfPersonalInjuriesCausedByWildfire" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_LandDamagedDueToWildfireInAcres" name="LandDamagedDueToWildfireInAcres" type="xbrli:integerItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_NumberOfInsurersClaimingCoverageDoesNotExist" name="NumberOfInsurersClaimingCoverageDoesNotExist" type="xbrli:integerItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
  <element id="pwr_SubsequentEventsAbstract" name="SubsequentEventsAbstract" abstract="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_SubsequentEventsDetailsAbstract" name="SubsequentEventsDetailsAbstract" abstract="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_SubsequentEventsTextualsAbstract" name="SubsequentEventsTextualsAbstract" abstract="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_McGregorConstructionGroupMember" name="McGregorConstructionGroupMember" type="us-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_SubsequentEventsAdditionalTextualsAbstract" name="SubsequentEventsAdditionalTextualsAbstract" abstract="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_OperatingUnitReorganization" name="OperatingUnitReorganization" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" />
  <element id="pwr_ReportingUnitsGoodwillBalance" name="ReportingUnitsGoodwillBalance" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" />
  <element id="pwr_DecreaseInFairValueOfReportingUnitsConsideredForImpairmentCalculation" name="DecreaseInFairValueOfReportingUnitsConsideredForImpairmentCalculation" type="us-types:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
  <element id="pwr_ExcessOfFairValueOverCarryingValueOfReportingUnits" name="ExcessOfFairValueOverCarryingValueOfReportingUnits" type="us-types:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
  <element id="pwr_AgreedAmountOfLoanToIndirectParentOfLlc" name="AgreedAmountOfLoanToIndirectParentOfLlc" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" />
  <element id="pwr_ValardConstructionLpMember" name="ValardConstructionLpMember" type="us-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_AdditionToIndefiniteLivedIntangibleAssets" name="AdditionToIndefiniteLivedIntangibleAssets" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" />
  <element id="pwr_InvestmentsInAffiliatesAndOtherEntitiesPolicyTextBlock" name="InvestmentsInAffiliatesAndOtherEntitiesPolicyTextBlock" type="us-types:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_ScheduleOfNewAccountingPronouncementAndChangesInAccountingPrinciplesTextBlock" name="ScheduleOfNewAccountingPronouncementAndChangesInAccountingPrinciplesTextBlock" type="us-types:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <element id="pwr_CommonStockRepurchasedRelatedToRepurchasePlanPolicyTextBlock" name="CommonStockRepurchasedRelatedToRepurchasePlanPolicyTextBlock" type="us-types:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
</schema>
