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

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2011-05-03</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001164552</issuerCik>
        <issuerName>Green Energy Management Services Holdings, Inc.</issuerName>
        <issuerTradingSymbol>GRMS</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001497177</rptOwnerCik>
            <rptOwnerName>GEM Lighting, L.L.C.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O GREEN ENERGY MANAGEMENT SERVICES, IN</rptOwnerStreet1>
            <rptOwnerStreet2>381 TEANECK ROAD</rptOwnerStreet2>
            <rptOwnerCity>TEANECK</rptOwnerCity>
            <rptOwnerState>NJ</rptOwnerState>
            <rptOwnerZipCode>07666</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, $0.0001 par value</value>
            </securityTitle>
            <transactionDate>
                <value>2011-05-03</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>20000000</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>45623216</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">20,000,000 shares were transferred by the Reporting Person to an affiliate of Ronald P. Ulfers, Jr., in consideration of Mr. Ulfers, Jr. being appointed as the Chairman, President and Chief Executive Officer and a director of the Issuer on April 6, 2011.</footnote>
        <footnote id="F2">All of the shares owned by the Reporting Person are beneficially owned by each of Deborah Samuel, the wife of Michael Samuel, a member of the board of directors of the Issuer, and Jonathan Samuel, Mr. Samuel's son. Ms. Samuel and Jonathan Samuel are the sole members of the Reporting Person. Michael Samuel does not have direct beneficial ownership of any of the Issuer's common stock.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Robert Weinstein, as attorney-in-fact for GEM Lighting, L.L.C.</signatureName>
        <signatureDate>2011-05-05</signatureDate>
    </ownerSignature>
</ownershipDocument>
