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

    <schemaVersion>X0203</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2009-02-18</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0001013871</issuerCik>
        <issuerName>NRG ENERGY, INC.</issuerName>
        <issuerTradingSymbol>NRG</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001456706</rptOwnerCik>
            <rptOwnerName>Bramnick Michael R.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>NRG ENERGY, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>211 CARNEGIE CENTER</rptOwnerStreet2>
            <rptOwnerCity>PRINCETON</rptOwnerCity>
            <rptOwnerState>NJ</rptOwnerState>
            <rptOwnerZipCode>08540</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Sr. VP &amp; General Counsel</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock, par value .01 per share</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>4300</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Non-Qualified Stock Options</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>27.915</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2007-01-03</value>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <value>2013-01-03</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, par value $.01 per share</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>3466</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Non-Qualified Stock Options</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>42.82</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2008-01-02</value>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <value>2014-01-02</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, par value $.01 per share</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>6200</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Non-Qualified Stock Options</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>23.64</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2009-01-02</value>
                <footnoteId id="F4"/>
            </exerciseDate>
            <expirationDate>
                <value>2015-01-02</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, par value $.01 per share</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>8900</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Performance Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F5"/>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2007-01-03</value>
            </exerciseDate>
            <expirationDate>
                <value>2017-01-03</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, par value $.01 per share</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>2400</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Performance Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F6"/>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2008-01-02</value>
            </exerciseDate>
            <expirationDate>
                <value>2018-01-02</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, par value $.01 per share</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>2400</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Performance Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F7"/>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2009-01-02</value>
            </exerciseDate>
            <expirationDate>
                <value>2019-01-02</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, par value $.01 per share</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>4200</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Includes the following securities issued to Mr. Bramnick by NRG Energy, Inc. under NRG's Long Term Incentive Plan.  Each RSU is equivalent in value to one share of NRG's Common Stock, par value $.01.  Mr. Bramnick will receive from NRG one such share of Common Stock, as follows: (i) 600 Restricted Stock Units (&quot;RSUs&quot;) issued on January 3, 2010; (ii) 600 RSUs issued on January 2, 2011; (iii) 1,100 RSUs issued on January 2, 2012.</footnote>
        <footnote id="F2">Pursuant to the Grant Agreement by and between NRG Energy, Inc. and Mr. Bramnick, half of the Stock Options vested and became exercisable on January 3, 2009.  The remaining balance will vest on January 3, 2010.</footnote>
        <footnote id="F3">Pursuant to the Grant Agreement by and between NRG Energy, Inc. and Mr. Bramnick, 33 1/3% of the Stock Options vested and became exercisable on January 2, 2009.  The remaining balance will vest as follows: 33 1/3% on January 2, 2010 and January 2, 2011.</footnote>
        <footnote id="F4">Pursuant to the Grant Agreement by and between NRG Energy, Inc. and Mr. Bramnick, the Stock Options will vest and become exercisable as follows: 33 1/3% on January 2, 2010; 33 1/3% on January 2, 2011 and 33 1/3% on January 2, 2012.</footnote>
        <footnote id="F5">Mr. Bramnick was issued 1,200 Performance Units by NRG Energy, Inc. under NRG Energy, Inc.'s Long Term Incentive Plan on January 3, 2007. Each Performance Unit will be paid out on January 3, 2010 if the average closing price of NRG Energy, Inc.'s Common Stock for the ten trading days prior to January 3, 2010 (the &quot;Measurement Price&quot;) is equal to or greater than $38.095 (the &quot;Target Price&quot;). The payout for each Performance Unit will be equal to: (i) one share of Common Stock, if the Measurement Price equals the Target Price; (ii) a prorated amount in between one and two shares of Common Stock, if the Measurement Price is greater than the Target Price but less than $44.74 (the &quot;Maximum Price&quot;); and (iii) two shares of Common Stock, if the Measurement Price is equal to or greater than the Maximum Price.</footnote>
        <footnote id="F6">Mr. Bramnick was issued 1,200 Performance Units by NRG Energy, Inc. under NRG Energy, Inc.'s Long Term Incentive Plan on January 2, 2008. Each Performance Unit will be paid out on January 2, 2011 if the average closing price of NRG Energy, Inc.'s Common Stock for the ten trading days prior to January 2, 2011(the &quot;Measurement Price&quot;) is equal to or greater than $60.16 (the &quot;Target Price&quot;). The payout for each Performance Unit will be equal to: (i) one share of Common Stock, if the Measurement Price equals the Target Price; (ii) a prorated amount in between one and two shares of Common Stock, if the Measurement Price is greater than the Target Price but less than $70.35 (the &quot;Maximum Price&quot;); and (iii) two shares of Common Stock, if the Measurement Price is equal to or greater than the Maximum Price.</footnote>
        <footnote id="F7">Mr. Bramnick was issued 2,100 Performance Units by NRG Energy, Inc. under NRG Energy, Inc.'s Long Term Incentive Plan on January 2, 2009. Each Performance Unit will be paid out on January 2, 2012 if the closing price of NRG's Common Stock January 2, 2012 (the &quot;Measurement Price&quot;) is equal to or greater than $30.61 (the &quot;Threshold Price&quot;). The payout for each PU will be equal to a pro-rated amount in between one-half and one share of common stock if the Measurement Price equals or exceeds the Threshold Price but less than $33.21 (the &quot;Target Price&quot;). The payout for each PU will be equal to a pro-rated amount in between one and two shares of common stock if the Measurement Price is equal to the Target Price but less than $38.84 (the &quot;Maximum Price&quot;). The payout for each PU will be equal to two shares of common stock if the Measurement Price is equal to or greater than the Maximum Price.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/Brian Curci, under Power of Attorney</signatureName>
        <signatureDate>2009-03-02</signatureDate>
    </ownerSignature>
</ownershipDocument>

