<SUBMISSION>
<ACCESSION-NUMBER>0001181431-12-049221
<TYPE>4
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20120906
<FILING-DATE>20120907
<DATE-OF-FILING-DATE-CHANGE>20120907
<ISSUER>
<COMPANY-DATA>
<CONFORMED-NAME>CALPINE CORP
<CIK>0000916457
<ASSIGNED-SIC>4911
<IRS-NUMBER>770212977
<STATE-OF-INCORPORATION>DE
<FISCAL-YEAR-END>1231
</COMPANY-DATA>
<BUSINESS-ADDRESS>
<STREET1>717 TEXAS AVENUE
<STREET2>SUITE 1000
<CITY>HOUSTON
<STATE>TX
<ZIP>77002
<PHONE>7138302000
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>717 TEXAS AVENUE
<STREET2>SUITE 1000
<CITY>HOUSTON
<STATE>TX
<ZIP>77002
</MAIL-ADDRESS>
</ISSUER>
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>Luminus Energy Partners Master Fund, Ltd.
<CIK>0001405850
<STATE-OF-INCORPORATION>D0
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>4
<ACT>34
<FILE-NUMBER>001-12079
<FILM-NUMBER>121079074
</FILING-VALUES>
<BUSINESS-ADDRESS>
<STREET1>1700 BROADWAY, 35TH FLOOR
<CITY>NEW YORK
<STATE>NY
<ZIP>10019
<PHONE>(212) 615-3450
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>1700 BROADWAY, 35TH FLOOR
<CITY>NEW YORK
<STATE>NY
<ZIP>10019
</MAIL-ADDRESS>
</REPORTING-OWNER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>rrd355457.xml
<DESCRIPTION>4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2012-09-06</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000916457</issuerCik>
        <issuerName>CALPINE CORP</issuerName>
        <issuerTradingSymbol>CPN</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001405850</rptOwnerCik>
            <rptOwnerName>Luminus Energy Partners Master Fund, Ltd.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>1700 BROADWAY</rptOwnerStreet1>
            <rptOwnerStreet2>38TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10019</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2012-09-06</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>2250000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>17.80</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>7050640</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F1"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Luminus Management, LLC is the manager of Luminus Energy Fund.  Due to its relationship with Luminus Energy Fund, Luminus Management, LLC may be deemed to have shared voting and investment power with respect to the shares owned by Luminus Energy Fund.  As such, Luminus Management, LLC may be deemed to have shared beneficial ownership of the shares of which Luminus Energy Fund is the owner.  Luminus Management, LLC however, disclaims beneficial ownership of such shares except to the extent of its pecuniary interest therein.  For further details relating to the Reporting Person's ownership structure, please refer to the Schedule 13D filed with the Securities and Exchange Commission on February 11, 2008, as last amended on September 7, 2012.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ By Luminus Management, LLC, Its Investment Manager, By Jonathan Barrett, President</signatureName>
        <signatureDate>2012-09-07</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SUBMISSION>
