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<?xml version="1.0" encoding="windows-1252"?> |
<ownershipDocument> |
| <schemaVersion> X0306 </schemaVersion> |
| <documentType> 4 </documentType> |
| <periodOfReport> 2022-08-30 </periodOfReport> |
| <notSubjectToSection16> 0 </notSubjectToSection16> |
| <issuer> |
| | <issuerCik> 0001161728 </issuerCik> |
| | <issuerName> MGE ENERGY INC </issuerName> |
| | <issuerTradingSymbol> MGEE </issuerTradingSymbol> |
| | </issuer> |
| <reportingOwner> |
| | <reportingOwnerId> |
| | | <rptOwnerCik> 0001732234 </rptOwnerCik> |
| | | <rptOwnerName> Berbee James G </rptOwnerName> |
| | | </reportingOwnerId> |
| | <reportingOwnerAddress> |
| | | <rptOwnerStreet1> 133 S BLAIR STREET </rptOwnerStreet1> |
| | | <rptOwnerStreet2> PO BOX 1231 </rptOwnerStreet2> |
| | | <rptOwnerCity> MADISON </rptOwnerCity> |
| | | <rptOwnerState> WI </rptOwnerState> |
| | | <rptOwnerZipCode> 53701-1231 </rptOwnerZipCode> |
| | | <rptOwnerStateDescription></rptOwnerStateDescription> |
| | | </reportingOwnerAddress> |
| | <reportingOwnerRelationship> |
| | | <isDirector> 1 </isDirector> |
| | | <isOfficer> 0 </isOfficer> |
| | | <isTenPercentOwner> 0 </isTenPercentOwner> |
| | | <isOther> 0 </isOther> |
| | | </reportingOwnerRelationship> |
| | </reportingOwner> |
| <nonDerivativeTable> |
| | <nonDerivativeTransaction> |
| | | <securityTitle> |
| <value> MGEE Common Stock </value> |
| </securityTitle> |
| | | <transactionDate> |
| <value> 2022-08-30 </value> |
| </transactionDate> |
| | | <transactionCoding> |
| <transactionFormType> 4 </transactionFormType> |
| <transactionCode> P </transactionCode> |
| <equitySwapInvolved> 0 </equitySwapInvolved> |
| </transactionCoding> |
| | | <transactionTimeliness> |
| <value></value> |
| </transactionTimeliness> |
| | | <transactionAmounts> |
| <transactionShares> |
| <value> 361.0015 </value> |
| </transactionShares> |
| <transactionPricePerShare> |
| <value> 78.8969 </value> |
| </transactionPricePerShare> |
| <transactionAcquiredDisposedCode> |
| <value> A </value> |
| </transactionAcquiredDisposedCode> |
| </transactionAmounts> |
| | | <postTransactionAmounts> |
| <sharesOwnedFollowingTransaction> |
| <value> 6330.833 </value> |
| <footnoteId id="F1"/> |
| </sharesOwnedFollowingTransaction> |
| </postTransactionAmounts> |
| | | <ownershipNature> |
| <directOrIndirectOwnership> |
| <value> D </value> |
| </directOrIndirectOwnership> |
| </ownershipNature> |
| | | </nonDerivativeTransaction> |
| | </nonDerivativeTable> |
| <footnotes> |
| | <footnote id="F1"> Includes shares acquired through dividend reinvestment. </footnote> |
| | </footnotes> |
| <ownerSignature> |
| | <signatureName> /s/ James G. Berbee </signatureName> |
| | <signatureDate> 2022-08-30 </signatureDate> |
| | </ownerSignature> |
| </ownershipDocument> |