<?xml version="1.0" encoding="UTF-8"?>
<!-- Documents rendered in XBRL format prepared by Certent CDM XBRL Version: 19.9.1 using Fujitsu Interstage XWand -->
<!-- Validation status: Passed -->
<linkbase xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.xbrl.org/2003/instance http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd" xmlns="http://www.xbrl.org/2003/linkbase" xmlns:xbrli="http://www.xbrl.org/2003/instance" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xbrldt="http://xbrl.org/2005/xbrldt">
    <roleRef roleURI="http://www.mgeenergy.com/role/DocumentDocumentAndEntityInformation" xlink:type="simple" xlink:href="mgee-20200420.xsd#ELRID_DocumentAndEntityInformation" />
    <arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all" />
    <arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default" />
    <arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain" />
    <arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member" />
    <arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension" />
    <definitionLink xlink:type="extended" xlink:role="http://www.mgeenergy.com/role/DocumentDocumentAndEntityInformation">
        <loc xlink:type="locator" xlink:href="mgee-20200420.xsd#mgee_DocumentAndEntityInformationAbstract" xlink:label="Locator_mgee_DocumentAndEntityInformationAbstract_59" />
        <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntitiesTable" xlink:label="Locator_dei_EntitiesTable_60" />
        <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="Locator_mgee_DocumentAndEntityInformationAbstract_59" xlink:to="Locator_dei_EntitiesTable_60" order="-1.0" xbrldt:contextElement="segment" xbrldt:closed="true" />
        <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntitiesTable" xlink:label="Locator_dei_EntitiesTable_61" />
        <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_LegalEntityAxis" xlink:label="Locator_dei_LegalEntityAxis_62" />
        <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="Locator_dei_EntitiesTable_61" xlink:to="Locator_dei_LegalEntityAxis_62" order="1.0" />
        <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_LegalEntityAxis" xlink:label="Locator_dei_LegalEntityAxis_63" />
        <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain" xlink:label="Locator_dei_EntityDomain_64" />
        <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="Locator_dei_LegalEntityAxis_63" xlink:to="Locator_dei_EntityDomain_64" order="1.0" />
        <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_LegalEntityAxis" xlink:label="Locator_dei_LegalEntityAxis_125" />
        <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain" xlink:label="Locator_dei_EntityDomain_126" />
        <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="Locator_dei_LegalEntityAxis_125" xlink:to="Locator_dei_EntityDomain_126" order="1.0" />
        <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain" xlink:label="Locator_dei_EntityDomain_65" />
        <loc xlink:type="locator" xlink:href="mgee-20200420.xsd#mgee_MgeMember" xlink:label="Locator_mgee_MgeMember_66" />
        <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="Locator_dei_EntityDomain_65" xlink:to="Locator_mgee_MgeMember_66" order="1.0" />
        <loc xlink:type="locator" xlink:href="mgee-20200420.xsd#mgee_DocumentAndEntityInformationAbstract" xlink:label="Locator_mgee_DocumentAndEntityInformationAbstract_67" />
        <loc xlink:type="locator" xlink:href="mgee-20200420.xsd#mgee_DocumentAndEntityInformationLineItems" xlink:label="Locator_mgee_DocumentAndEntityInformationLineItems_68" />
        <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="Locator_mgee_DocumentAndEntityInformationAbstract_67" xlink:to="Locator_mgee_DocumentAndEntityInformationLineItems_68" order="1.0" />
        <loc xlink:type="locator" xlink:href="mgee-20200420.xsd#mgee_DocumentAndEntityInformationLineItems" xlink:label="Locator_mgee_DocumentAndEntityInformationLineItems_69" />
        <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityRegistrantName" xlink:label="Locator_dei_EntityRegistrantName_70" />
        <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="Locator_mgee_DocumentAndEntityInformationLineItems_69" xlink:to="Locator_dei_EntityRegistrantName_70" order="1.0" />
        <loc xlink:type="locator" xlink:href="mgee-20200420.xsd#mgee_DocumentAndEntityInformationLineItems" xlink:label="Locator_mgee_DocumentAndEntityInformationLineItems_71" />
        <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityCentralIndexKey" xlink:label="Locator_dei_EntityCentralIndexKey_72" />
        <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="Locator_mgee_DocumentAndEntityInformationLineItems_71" xlink:to="Locator_dei_EntityCentralIndexKey_72" order="2.0" />
        <loc xlink:type="locator" xlink:href="mgee-20200420.xsd#mgee_DocumentAndEntityInformationLineItems" xlink:label="Locator_mgee_DocumentAndEntityInformationLineItems_73" />
        <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_DocumentType" xlink:label="Locator_dei_DocumentType_74" />
        <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="Locator_mgee_DocumentAndEntityInformationLineItems_73" xlink:to="Locator_dei_DocumentType_74" order="3.0" />
        <loc xlink:type="locator" xlink:href="mgee-20200420.xsd#mgee_DocumentAndEntityInformationLineItems" xlink:label="Locator_mgee_DocumentAndEntityInformationLineItems_75" />
        <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_DocumentPeriodEndDate" xlink:label="Locator_dei_DocumentPeriodEndDate_76" />
        <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="Locator_mgee_DocumentAndEntityInformationLineItems_75" xlink:to="Locator_dei_DocumentPeriodEndDate_76" order="4.0" />
        <loc xlink:type="locator" xlink:href="mgee-20200420.xsd#mgee_DocumentAndEntityInformationLineItems" xlink:label="Locator_mgee_DocumentAndEntityInformationLineItems_77" />
        <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_AmendmentFlag" xlink:label="Locator_dei_AmendmentFlag_78" />
        <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="Locator_mgee_DocumentAndEntityInformationLineItems_77" xlink:to="Locator_dei_AmendmentFlag_78" order="5.0" />
        <loc xlink:type="locator" xlink:href="mgee-20200420.xsd#mgee_DocumentAndEntityInformationLineItems" xlink:label="Locator_mgee_DocumentAndEntityInformationLineItems_79" />
        <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_TradingSymbol" xlink:label="Locator_dei_TradingSymbol_80" />
        <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="Locator_mgee_DocumentAndEntityInformationLineItems_79" xlink:to="Locator_dei_TradingSymbol_80" order="6.0" />
        <loc xlink:type="locator" xlink:href="mgee-20200420.xsd#mgee_DocumentAndEntityInformationLineItems" xlink:label="Locator_mgee_DocumentAndEntityInformationLineItems_81" />
        <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_DocumentFiscalYearFocus" xlink:label="Locator_dei_DocumentFiscalYearFocus_82" />
        <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="Locator_mgee_DocumentAndEntityInformationLineItems_81" xlink:to="Locator_dei_DocumentFiscalYearFocus_82" order="7.0" />
        <loc xlink:type="locator" xlink:href="mgee-20200420.xsd#mgee_DocumentAndEntityInformationLineItems" xlink:label="Locator_mgee_DocumentAndEntityInformationLineItems_83" />
        <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_DocumentFiscalPeriodFocus" xlink:label="Locator_dei_DocumentFiscalPeriodFocus_84" />
        <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="Locator_mgee_DocumentAndEntityInformationLineItems_83" xlink:to="Locator_dei_DocumentFiscalPeriodFocus_84" order="8.0" />
        <loc xlink:type="locator" xlink:href="mgee-20200420.xsd#mgee_DocumentAndEntityInformationLineItems" xlink:label="Locator_mgee_DocumentAndEntityInformationLineItems_85" />
        <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_CurrentFiscalYearEndDate" xlink:label="Locator_dei_CurrentFiscalYearEndDate_86" />
        <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="Locator_mgee_DocumentAndEntityInformationLineItems_85" xlink:to="Locator_dei_CurrentFiscalYearEndDate_86" order="9.0" />
        <loc xlink:type="locator" xlink:href="mgee-20200420.xsd#mgee_DocumentAndEntityInformationLineItems" xlink:label="Locator_mgee_DocumentAndEntityInformationLineItems_87" />
        <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityEmergingGrowthCompany" xlink:label="Locator_dei_EntityEmergingGrowthCompany_88" />
        <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="Locator_mgee_DocumentAndEntityInformationLineItems_87" xlink:to="Locator_dei_EntityEmergingGrowthCompany_88" order="10.0" />
        <loc xlink:type="locator" xlink:href="mgee-20200420.xsd#mgee_DocumentAndEntityInformationLineItems" xlink:label="Locator_mgee_DocumentAndEntityInformationLineItems_89" />
        <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityExTransitionPeriod" xlink:label="Locator_dei_EntityExTransitionPeriod_90" />
        <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="Locator_mgee_DocumentAndEntityInformationLineItems_89" xlink:to="Locator_dei_EntityExTransitionPeriod_90" order="11.0" />
        <loc xlink:type="locator" xlink:href="mgee-20200420.xsd#mgee_DocumentAndEntityInformationLineItems" xlink:label="Locator_mgee_DocumentAndEntityInformationLineItems_91" />
        <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_SecurityExchangeName" xlink:label="Locator_dei_SecurityExchangeName_92" />
        <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="Locator_mgee_DocumentAndEntityInformationLineItems_91" xlink:to="Locator_dei_SecurityExchangeName_92" order="12.0" />
        <loc xlink:type="locator" xlink:href="mgee-20200420.xsd#mgee_DocumentAndEntityInformationLineItems" xlink:label="Locator_mgee_DocumentAndEntityInformationLineItems_93" />
        <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_Security12bTitle" xlink:label="Locator_dei_Security12bTitle_94" />
        <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="Locator_mgee_DocumentAndEntityInformationLineItems_93" xlink:to="Locator_dei_Security12bTitle_94" order="13.0" />
        <loc xlink:type="locator" xlink:href="mgee-20200420.xsd#mgee_DocumentAndEntityInformationLineItems" xlink:label="Locator_mgee_DocumentAndEntityInformationLineItems_95" />
        <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityTaxIdentificationNumber" xlink:label="Locator_dei_EntityTaxIdentificationNumber_96" />
        <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="Locator_mgee_DocumentAndEntityInformationLineItems_95" xlink:to="Locator_dei_EntityTaxIdentificationNumber_96" order="14.0" />
        <loc xlink:type="locator" xlink:href="mgee-20200420.xsd#mgee_DocumentAndEntityInformationLineItems" xlink:label="Locator_mgee_DocumentAndEntityInformationLineItems_97" />
        <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityFileNumber" xlink:label="Locator_dei_EntityFileNumber_98" />
        <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="Locator_mgee_DocumentAndEntityInformationLineItems_97" xlink:to="Locator_dei_EntityFileNumber_98" order="15.0" />
        <loc xlink:type="locator" xlink:href="mgee-20200420.xsd#mgee_DocumentAndEntityInformationLineItems" xlink:label="Locator_mgee_DocumentAndEntityInformationLineItems_99" />
        <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityAddressAddressLine1" xlink:label="Locator_dei_EntityAddressAddressLine1_100" />
        <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="Locator_mgee_DocumentAndEntityInformationLineItems_99" xlink:to="Locator_dei_EntityAddressAddressLine1_100" order="16.0" />
        <loc xlink:type="locator" xlink:href="mgee-20200420.xsd#mgee_DocumentAndEntityInformationLineItems" xlink:label="Locator_mgee_DocumentAndEntityInformationLineItems_101" />
        <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityAddressCityOrTown" xlink:label="Locator_dei_EntityAddressCityOrTown_102" />
        <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="Locator_mgee_DocumentAndEntityInformationLineItems_101" xlink:to="Locator_dei_EntityAddressCityOrTown_102" order="17.0" />
        <loc xlink:type="locator" xlink:href="mgee-20200420.xsd#mgee_DocumentAndEntityInformationLineItems" xlink:label="Locator_mgee_DocumentAndEntityInformationLineItems_103" />
        <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityAddressStateOrProvince" xlink:label="Locator_dei_EntityAddressStateOrProvince_104" />
        <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="Locator_mgee_DocumentAndEntityInformationLineItems_103" xlink:to="Locator_dei_EntityAddressStateOrProvince_104" order="18.0" />
        <loc xlink:type="locator" xlink:href="mgee-20200420.xsd#mgee_DocumentAndEntityInformationLineItems" xlink:label="Locator_mgee_DocumentAndEntityInformationLineItems_105" />
        <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityAddressCountry" xlink:label="Locator_dei_EntityAddressCountry_106" />
        <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="Locator_mgee_DocumentAndEntityInformationLineItems_105" xlink:to="Locator_dei_EntityAddressCountry_106" order="19.0" />
        <loc xlink:type="locator" xlink:href="mgee-20200420.xsd#mgee_DocumentAndEntityInformationLineItems" xlink:label="Locator_mgee_DocumentAndEntityInformationLineItems_107" />
        <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityAddressPostalZipCode" xlink:label="Locator_dei_EntityAddressPostalZipCode_108" />
        <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="Locator_mgee_DocumentAndEntityInformationLineItems_107" xlink:to="Locator_dei_EntityAddressPostalZipCode_108" order="20.0" />
        <loc xlink:type="locator" xlink:href="mgee-20200420.xsd#mgee_DocumentAndEntityInformationLineItems" xlink:label="Locator_mgee_DocumentAndEntityInformationLineItems_109" />
        <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_CityAreaCode" xlink:label="Locator_dei_CityAreaCode_110" />
        <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="Locator_mgee_DocumentAndEntityInformationLineItems_109" xlink:to="Locator_dei_CityAreaCode_110" order="21.0" />
        <loc xlink:type="locator" xlink:href="mgee-20200420.xsd#mgee_DocumentAndEntityInformationLineItems" xlink:label="Locator_mgee_DocumentAndEntityInformationLineItems_111" />
        <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_LocalPhoneNumber" xlink:label="Locator_dei_LocalPhoneNumber_112" />
        <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="Locator_mgee_DocumentAndEntityInformationLineItems_111" xlink:to="Locator_dei_LocalPhoneNumber_112" order="22.0" />
        <loc xlink:type="locator" xlink:href="mgee-20200420.xsd#mgee_DocumentAndEntityInformationLineItems" xlink:label="Locator_mgee_DocumentAndEntityInformationLineItems_113" />
        <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_WrittenCommunications" xlink:label="Locator_dei_WrittenCommunications_114" />
        <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="Locator_mgee_DocumentAndEntityInformationLineItems_113" xlink:to="Locator_dei_WrittenCommunications_114" order="23.0" />
        <loc xlink:type="locator" xlink:href="mgee-20200420.xsd#mgee_DocumentAndEntityInformationLineItems" xlink:label="Locator_mgee_DocumentAndEntityInformationLineItems_115" />
        <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_SolicitingMaterial" xlink:label="Locator_dei_SolicitingMaterial_116" />
        <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="Locator_mgee_DocumentAndEntityInformationLineItems_115" xlink:to="Locator_dei_SolicitingMaterial_116" order="24.0" />
        <loc xlink:type="locator" xlink:href="mgee-20200420.xsd#mgee_DocumentAndEntityInformationLineItems" xlink:label="Locator_mgee_DocumentAndEntityInformationLineItems_117" />
        <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_PreCommencementIssuerTenderOffer" xlink:label="Locator_dei_PreCommencementIssuerTenderOffer_118" />
        <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="Locator_mgee_DocumentAndEntityInformationLineItems_117" xlink:to="Locator_dei_PreCommencementIssuerTenderOffer_118" order="25.0" />
        <loc xlink:type="locator" xlink:href="mgee-20200420.xsd#mgee_DocumentAndEntityInformationLineItems" xlink:label="Locator_mgee_DocumentAndEntityInformationLineItems_119" />
        <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_PreCommencementTenderOffer" xlink:label="Locator_dei_PreCommencementTenderOffer_120" />
        <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="Locator_mgee_DocumentAndEntityInformationLineItems_119" xlink:to="Locator_dei_PreCommencementTenderOffer_120" order="26.0" />
        <loc xlink:type="locator" xlink:href="mgee-20200420.xsd#mgee_DocumentAndEntityInformationLineItems" xlink:label="Locator_mgee_DocumentAndEntityInformationLineItems_121" />
        <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityIncorporationStateCountryCode" xlink:label="Locator_dei_EntityIncorporationStateCountryCode_122" />
        <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="Locator_mgee_DocumentAndEntityInformationLineItems_121" xlink:to="Locator_dei_EntityIncorporationStateCountryCode_122" order="27.0" />
        <loc xlink:type="locator" xlink:href="mgee-20200420.xsd#mgee_DocumentAndEntityInformationLineItems" xlink:label="Locator_mgee_DocumentAndEntityInformationLineItems_123" />
        <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityInformationFormerLegalOrRegisteredName" xlink:label="Locator_dei_EntityInformationFormerLegalOrRegisteredName_124" />
        <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="Locator_mgee_DocumentAndEntityInformationLineItems_123" xlink:to="Locator_dei_EntityInformationFormerLegalOrRegisteredName_124" order="28.0" />
    </definitionLink>
</linkbase>
