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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2015-06-25</periodOfReport>

    <dateOfOriginalSubmission>2015-06-29</dateOfOriginalSubmission>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001425565</issuerCik>
        <issuerName>Real Goods Solar, Inc.</issuerName>
        <issuerTradingSymbol>RGSE</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001539124</rptOwnerCik>
            <rptOwnerName>Riverside Renewable Energy Investments, LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O RIVERSIDE PARTNERS, LLC</rptOwnerStreet1>
            <rptOwnerStreet2>699 BOYLSTON STREET, 8TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>BOSTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02116</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class A Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2015-06-25</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>910000</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>3.29</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1301533</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">This amendment corrects the number of shares actually issued to Riverside Renewable Energy Investments, LLC (the &quot;Company&quot;), pursuant to the Conversion Agreement, by and between Riverside Fund III, L.P. (the &quot;Fund&quot;) and Real Goods Solar, Inc. (the &quot;Issuer&quot;) (the &quot;Conversion Agreement&quot;), and assigned by the Fund to the Company on June 25, 2015.  On the original Form 4, the Company reported that 915,000 shares of Class A Common Stock of the Issuer were issued to the Company pursuant to the Conversion Agreement upon the conversion of certain indebtedness of the Fund into the right to receive shares, when, in fact, 910,000 shares of Class A Common Stock were actually issued to the Company upon such conversion.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ David L. Belluck, Manager of Riverside Renewable Energy Investments, LLC</signatureName>
        <signatureDate>2015-07-16</signatureDate>
    </ownerSignature>
</ownershipDocument>
