<SUBMISSION>
<ACCESSION-NUMBER>0001140361-15-030790
<TYPE>3
<PUBLIC-DOCUMENT-COUNT>2
<PERIOD>20150801
<FILING-DATE>20150810
<DATE-OF-FILING-DATE-CHANGE>20150810
<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>Koshkin Jeff
<CIK>0001644377
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>3
<ACT>34
<FILE-NUMBER>001-12079
<FILM-NUMBER>151041763
</FILING-VALUES>
<MAIL-ADDRESS>
<STREET1>717 TEXAS AVENUE, SUITE 1000
<CITY>HOUSTON
<STATE>TX
<ZIP>77002
</MAIL-ADDRESS>
</REPORTING-OWNER>
<DOCUMENT>
<TYPE>3
<SEQUENCE>1
<FILENAME>doc1.xml
<DESCRIPTION>FORM 3
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0206</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2015-08-01</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001644377</rptOwnerCik>
            <rptOwnerName>Koshkin Jeff</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O CALPINE CORPORATION</rptOwnerStreet1>
            <rptOwnerStreet2>717 TEXAS AVENUE, SUITE 1000</rptOwnerStreet2>
            <rptOwnerCity>HOUSTON</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>77002</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>SVP, CHIEF ACCOUNTING OFFICER</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock, par value $0.001 per share</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>26168</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Employee Stock Option (right to buy)</value>
                <footnoteId id="F2"/>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>8.36</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2011-12-02</value>
            </exerciseDate>
            <expirationDate>
                <value>2018-12-02</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, par value $0.001 per share</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>4779</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Employee Stock Option (right to buy)</value>
                <footnoteId id="F2"/>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>11.24</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2013-02-24</value>
            </exerciseDate>
            <expirationDate>
                <value>2020-02-24</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, par value $0.001 per share</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>16455</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Employee Stock Option (right to buy)</value>
                <footnoteId id="F2"/>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>14.30</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2014-02-14</value>
            </exerciseDate>
            <expirationDate>
                <value>2021-02-14</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, par value $0.001 per share</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>13968</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Employee Stock Option (right to buy)</value>
                <footnoteId id="F2"/>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>15.31</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2015-02-28</value>
            </exerciseDate>
            <expirationDate>
                <value>2022-02-28</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, par value $0.001 per share</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>14482</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Includes 11,313 shares of restricted stock awarded purusuant to Calpine Corporation's (the &quot;Issuer&quot;) Amended and Restated 2008 Equity Plan (the &quot;Equity Plan&quot;) of which 1,975 shares vest on February 28, 2016, 3,926 shares vest in two equal installments on February 26, 2016 and 2017, and 5,412 shares vest in three equal installments on February 28, 2016, 2017, and 2018.</footnote>
        <footnote id="F2">Granted pursuant to the Issuer's Equity Plan.  The option became vested and exercisable on the third anniversary date of the grant date.</footnote>
    </footnotes>

    <remarks>Exhibit 24.1 Power of Attorney</remarks>

    <ownerSignature>
        <signatureName>/s/ W. Thaddeus Miller by Power of Attorney</signatureName>
        <signatureDate>2015-08-10</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
<DOCUMENT>
<TYPE>EX-24.1
<SEQUENCE>2
<FILENAME>poaforjeffkoshkin.txt
<DESCRIPTION>POWER OF ATTORNEY
<TEXT>
                                POWER OF ATTORNEY


         KNOW ALL MEN BY THESE PRESENTS, that the undersigned hereby constitutes
and appoints W. Thaddeus Miller, and Zamir Rauf and each of them, his true and
lawful attorney-in-fact to:

         (1) execute for and on behalf of the undersigned, in the undersigned's
capacity as an officer and/or director of Calpine Corporation (the "Company"),
any and all Forms 3, 4 and 5 required to be filed by the undersigned in
accordance with Section 16(a) of the Securities Exchange Act of 1934, as amended
(the "1934 Act"), and the rules thereunder;

         (2) do and perform any and all acts for and on behalf of the
undersigned which may be necessary or desirable to complete and execute any such
Forms 3, 4 or 5 and timely file each form with the United States Securities and
Exchange Commission and any stock exchange or similar authority; and

         (3) take and other action of any type whatsoever in connection with the
foregoing which, in the opinion of either such attorney-in-fact, may be of
benefit to, in the best interest of, or legally required by, the undersigned, it
being understood that the documents executed by either such attorney-in-fact on
behalf of the undersigned, pursuant to this attorney-in-fact may approve in
his discretion.

         The undersigned hereby grants to such attorney-in-fact, and any one of
them, full power and authority to do and perform all and every act and thing
whatsoever requisite, necessary, and proper to be done in the exercise of any of
the rights and powers herein granted, as fully to all intents and purposes and
the undersigned might or could do if personally present, with full power of
substitution or revocation, hereby ratifying and confirming all that such
attorney-in-fact, or her substitute or substitutes, shall lawfully do or cause
to be done by virtue of the Power of Attorney and the rights and powers herein
granted. The undersigned acknowledges that none of such attorneys-in-fact, in
serving in such capacity at the request of the undersigned, is hereby assuming,
nor is the Company hereby assuming, any of the undersigned's responsibilities to
comply with Section 16 of the 1934 Act.

         This Power of Attorney shall remain in full force and effect until the
undersigned is no longer required to file Forms 3, 4 and 5 with respect to the
undersigned's holdings of and transactions in securities issued by the Company,
unless earlier revoked by the undersigned in a signed writing delivered to the
foregoing attorneys-in-fact.

         IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney
to be executed as of this 4th day of June 2015.


                                        /s/ Jeff Koshkin
                                        ----------------------
                                        Jeff Koshkin
</TEXT>
</DOCUMENT>
</SUBMISSION>
