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

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2006-07-06</periodOfReport>

    <issuer>
        <issuerCik>0001047862</issuerCik>
        <issuerName>CONSOLIDATED EDISON INC</issuerName>
        <issuerTradingSymbol>ED</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001108889</rptOwnerCik>
            <rptOwnerName>DEL GIUDICE MICHAEL J</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>MILLENNIUM CREDIT MARKETS, LLC</rptOwnerStreet1>
            <rptOwnerStreet2>15 WEST 48TH STREET</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10020</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2006-06-30</value>
            </transactionDate>
            <deemedExecutionDate>
                <value>2006-07-06</value>
            </deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>11.9951</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>44.0211</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>15506.5745</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Includes shares of common stock of Consolidated Edison, Inc. (the &quot;Company&quot;) acquired pursuant to the dividend reinvestment provision of the Company's Stock Purchase Plan.</footnote>
        <footnote id="F2">Total includes 138.883 Deferred Stock Units acquired pursuant to the dividend reinvestment feature of the Company's Long Term Incentive Plan and 13.3472 shares acquired pursuant to the Company's Automatic Dividend Reinvestment and Cash Payment Plan.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Peter J. Barrett;  Attorney-in-Fact</signatureName>
        <signatureDate>2006-07-10</signatureDate>
    </ownerSignature>
</ownershipDocument>
