<SUBMISSION>
<ACCESSION-NUMBER>0001209191-05-028588
<TYPE>4
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20050525
<FILING-DATE>20050526
<DATE-OF-FILING-DATE-CHANGE>20050526
<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>50 WEST SAN FERNANDO ST
<CITY>SAN JOSE
<STATE>CA
<ZIP>95113
<PHONE>4089955115
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>50 W SAN FERNANDO
<STREET2>SUITE 500
<CITY>SAN JOSE
<STATE>CA
<ZIP>95113
</MAIL-ADDRESS>
</ISSUER>
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>GARTEN JEFFREY E
<CIK>0001181532
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>4
<ACT>34
<FILE-NUMBER>001-12079
<FILM-NUMBER>05861483
</FILING-VALUES>
<BUSINESS-ADDRESS>
<STREET1>C/O AETNA IN CORP SECRETARYS OFFICE
<STREET2>151 FARMINGTON AVENUE RC4A
<CITY>HARTFORD
<STATE>CT
<ZIP>06156
<PHONE>860273338
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>C/O AETNA INC CORP SECRETARYS OFFICE
<STREET2>151 FARMINGTON AVENUE RC4A
<CITY>HARTFORD
<STATE>CT
<ZIP>06156
</MAIL-ADDRESS>
</REPORTING-OWNER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>bpa09558_bpa2jg.xml
<DESCRIPTION>MAIN DOCUMENT DESCRIPTION
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2005-05-25</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001181532</rptOwnerCik>
            <rptOwnerName>GARTEN JEFFREY E</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>DEAN, SCHOOL OF MANAGEMENT</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>NEW HAVEN</rptOwnerCity>
            <rptOwnerState>CT</rptOwnerState>
            <rptOwnerZipCode>06520</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Non-Qualified Stock Option (right to buy)</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>2.64</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2005-05-25</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>25000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2005-05-25</value>
            </exerciseDate>
            <expirationDate>
                <value>2015-05-25</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>25000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>25000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Grant to reporting person of exempt Rule 16b-3 option under the Automatic Grant Program of the Issuer's 1996 Stock Incentive Plan. The option is immediately exercisable for all of the option shares. The option shares will, however, vest upon completion of one (1) year of continued service as a member of the Issuer's board of Directors measured from the grant date.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>By: Lisa Bodensteiner  For: Jeffery E. Garten</signatureName>
        <signatureDate>2005-05-26</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SUBMISSION>
