<SUBMISSION>
<ACCESSION-NUMBER>0001181431-12-030670
<TYPE>4
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20120515
<FILING-DATE>20120517
<DATE-OF-FILING-DATE-CHANGE>20120517
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>RYAN J. STUART
<CIK>0001425020
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>4
<ACT>34
<FILE-NUMBER>001-12079
<FILM-NUMBER>12852463
</FILING-VALUES>
<MAIL-ADDRESS>
<STREET1>717 TEXAS AVENUE
<CITY>HOUSTON
<STATE>TX
<ZIP>77002
</MAIL-ADDRESS>
</REPORTING-OWNER>
<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>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>rrd345551.xml
<DESCRIPTION>JSR CALPINE RSU 5.15.12
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0305</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2012-05-15</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001425020</rptOwnerCik>
            <rptOwnerName>RYAN J. STUART</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>591 REDWOOD HIGHWAY, SUITE 3215</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>MILL VALLEY</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94941</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2012-05-15</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>8036</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>77509375</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnotes</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Represents award of restricted stock units pursuant to Calpine Corporation's 2008 Director Incentive Plan.  The award vests on the earlier to occur of (i) the first anniversary of the grant date or (ii) the day immediately preceding the date of the 2013 annual meeting of stockholders.  The shares become payable on the earliest to occur of (i) the reporting person's elected distribution date, (ii) the consummation of a change in control, or (iii) upon termination of service on the board of directors.  Each restricted stock unit represents a contingent right to receive one share of Calpine Corporation common stock.  The restricted stock units are payable solely in common stock.  This award of restricted stock units was made to J. Stuart Ryan (&quot;JSR&quot;) as a Director and Chairman of the Board of the Issuer.  These units are in addition to 23,802 restricted stock units previously awarded to JSR.  Additionally, JSR directly owns 5,029 shares of the Issuer's common stock.</footnote>
        <footnote id="F2">Additionally, 70,541,012 shares of the Issuer's common stock are owned directly by SPO Partners II, L.P. (&quot;SPO Partners&quot;), and may be deemed to be indirectly beneficially owned by (i) SPO Advisory Partners, L.P. (&quot;SPO Advisory&quot;), the sole general partner of SPO Partners, (ii) SPO Advisory Corp. (&quot;SPO Corp.&quot;), the sole general partner of SPO Advisory, and (iii) John H. Scully (&quot;JHS&quot;) and Edward H. McDermott (&quot;EHM&quot;), the two controlling persons of SPO Corp.  Additionally, 2,697,096 shares of the Issuer's common stock are owned directly by San Francisco Partners, L.P. (&quot;SF Partners&quot;), and may be deemed to be indirectly beneficially owned by (i) SF Advisory Partners, L.P. (&quot;SF Advisory&quot;), the sole general partner of SF Partners, (ii) SPO Corp., the sole general partner of SF Advisory, and (iii) JHS and EHM, the two controlling persons of SPO Corp.</footnote>
        <footnote id="F3">Additionally, 4,234,400 shares of the Issuer's common stock are owned directly by SPO Partners II Co-Investment Partnership, L.P. (&quot;SPO Co-Invest&quot;), and may be deemed to be indirectly beneficially owned by (i) SPO Advisory, the sole general partner of SPO Co-Invest, (ii) SPO Corp., the sole general partner of SPO Advisory, and (iii) JHS and EHM, the two controlling persons of SPO Corp.  Additionally, JHS owns 5,000 shares of the Issuer's common stock in his IRA, which is self-directed.  Additionally, EHM owns 5,600 shares of the Issuer's common stock in his IRA, which is self-directed.</footnote>
        <footnote id="F4">Additionally, these shares may be deemed to be indirectly beneficially owned by JSR and his investment vehicle, Rydout LLC (&quot;Rydout&quot;), solely in his advisory capacity to SPO Corp., with respect to investments by SPO Partners, SF Partners, and SPO Co-Invest in securities of Calpine Corporation.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Kim M. Silva</signatureName>
        <signatureDate>2012-05-17</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SUBMISSION>
