<SUBMISSION>
<ACCESSION-NUMBER>0001140361-14-021964
<TYPE>3
<PUBLIC-DOCUMENT-COUNT>2
<PERIOD>20140514
<FILING-DATE>20140516
<DATE-OF-FILING-DATE-CHANGE>20140516
<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>ADAMS JOHN M
<CIK>0001606758
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>3
<ACT>34
<FILE-NUMBER>001-12079
<FILM-NUMBER>14852124
</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>2014-05-14</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001606758</rptOwnerCik>
            <rptOwnerName>ADAMS JOHN M</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>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>EVP, Power Ops</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock, par value $0.001 per share</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>43249</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Option (Right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>11.74</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <value>2020-04-19</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>42270</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Option (Right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>14.30</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <value>2021-02-14</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>49922</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Option (Right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>15.31</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F4"/>
            </exerciseDate>
            <expirationDate>
                <value>2022-02-28</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>41770</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Includes restricted stock awarded pursuant to Calpine Corporation's  Amended and Restated 2008 Equity Incentive Plan (the &quot;Issuer's Equity Plan&quot;) of which 7,177 shares are fully vested, 6,416 shares vest on February 28, 2015, 10,818 shares vest in two equal instalments on February 28 in years 2015 and 2016, and 18,838 shares vest in three equal instalments on February 26 in years 2015, 2016 and 2017.</footnote>
        <footnote id="F2">On April 19, 2010, a grant of an option pursuant to the Issuer's Equity Plan.  The option becomes vested and exercisable on the third anniversary date of the grant date.</footnote>
        <footnote id="F3">On February 14, 2011, a grant of an option pursuant to the Issuer's Equity Plan.  The option becomes vested and exercisable on the third anniversary date of the grant date.</footnote>
        <footnote id="F4">On February 29, 2012, a grant of an option pursuant to the Issuer's Equity Plan.  The option becomes 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>2014-05-16</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
<DOCUMENT>
<TYPE>EX-24.1
<SEQUENCE>2
<FILENAME>poa1.htm
<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 Jim. D. Deidiker, 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 24th day of April 2014.


                                        /s/ John M. Adams
                                        ----------------------
                                        John M. Adams

</TEXT>
</DOCUMENT>
</SUBMISSION>
