<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2018-06-04</periodOfReport>

    <notSubjectToSection16>1</notSubjectToSection16>

    <issuer>
        <issuerCik>0001143068</issuerCik>
        <issuerName>GREAT PLAINS ENERGY INC</issuerName>
        <issuerTradingSymbol>GXP</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001674504</rptOwnerCik>
            <rptOwnerName>PRICE SANDRA J</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O GREAT PLAINS ENERGY INCORPORATED</rptOwnerStreet1>
            <rptOwnerStreet2>1200 MAIN STREET</rptOwnerStreet2>
            <rptOwnerCity>KANSAS CITY</rptOwnerCity>
            <rptOwnerState>MO</rptOwnerState>
            <rptOwnerZipCode>64105</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Director Deferred Share Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2018-06-04</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>8037</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F1"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>8037</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Director Deferred Share units are granted under the Long-Term Incentive Plan. Each unit represents the right to receive one share of Great Plains Energy Incorporated (&quot;Great Plains Energy&quot;) Common Stock, plus stock reflecting reinvested dividends. Units are converted to stock and distributed following termination of service on the Board pursuant to elections made by the reporting person.</footnote>
        <footnote id="F2">The Great Plains Energy Director Deferred Share units were exchanged for Evergy, Inc. (&quot;Evergy&quot;) (formerly Monarch Energy Holding, Inc.) Director Deferred Share units pursuant to the Amended and Restated Agreement and Plan of Merger dated as of July 9, 2017 by and among Great Plains Energy, Westar Energy, Inc., Evergy, King Energy, Inc., and for certain limited purposes, GP Star, Inc. at an exchange ratio of 0.5981 for each Great Plains Energy share.  On the effective date of the merger, the closing price of Great Plains Energy's common stock was $31.99 per share, and Evergy's common stock had not yet commenced trading on the New York Stock Exchange.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Executed on behalf of Sandra J. Price by Jaileah X. Huddleston, attorney-in-fact</signatureName>
        <signatureDate>2018-06-05</signatureDate>
    </ownerSignature>
</ownershipDocument>
