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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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<SEC-DOCUMENT>0001140361-10-033482.txt : 20100813
<SEC-HEADER>0001140361-10-033482.hdr.sgml : 20100813
<ACCEPTANCE-DATETIME>20100813192426
ACCESSION NUMBER:		0001140361-10-033482
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20100811
FILED AS OF DATE:		20100813
DATE AS OF CHANGE:		20100813

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Hill Thad
		CENTRAL INDEX KEY:			0001351761

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-12079
		FILM NUMBER:		101016701

	MAIL ADDRESS:	
		STREET 1:		1301 MCKINNEY
		STREET 2:		SUITE 2300
		CITY:			HOUSTON
		STATE:			TX
		ZIP:			77010

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			CALPINE CORP
		CENTRAL INDEX KEY:			0000916457
		STANDARD INDUSTRIAL CLASSIFICATION:	ELECTRIC SERVICES [4911]
		IRS NUMBER:				770212977
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		717 TEXAS AVENUE
		STREET 2:		SUITE 1000
		CITY:			HOUSTON
		STATE:			TX
		ZIP:			77002
		BUSINESS PHONE:		7138308775

	MAIL ADDRESS:	
		STREET 1:		717 TEXAS AVENUE
		STREET 2:		SUITE 1000
		CITY:			HOUSTON
		STATE:			TX
		ZIP:			77002
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>doc1.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2010-08-11</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001351761</rptOwnerCik>
            <rptOwnerName>Hill Thad</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 &amp; CHIEF COMMERCIAL OFFICER</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable></nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Employee Stock Option (right to buy)</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>12.64</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2010-08-11</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>900000</value>
                    <footnoteId id="F2"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.00</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2013-08-11</value>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2015-09-01</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, par value $0.001 per share</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>900000</value>
                    <footnoteId id="F2"/>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>900000</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Grant of option pursuant to Calpine Corporation's Amended and Restated 2008 Equity Incentive Plan (&quot;Option&quot;).  The Option shall become fully vested and exercisable on August 11, 2013, subject to Mr. Hill's continuous employment with Calpine Corporation during that period.</footnote>
        <footnote id="F2">If on the date of exercise of the Option, the New York Stock Exchange closing price of a share of Calpine Corporation's Common Stock exceeds the exercise price plus 25% ($15.80), then the number of shares underlying the Option that may be exercised on that date of exercise shall be reduced, on a straight-line basis, beginning when such closing price on the date of exercise exceeds $15.80 and ending when such closing price equals or exceeds $27.50 per share at which closing price the number of shares underlying the Option shall be reduced to zero shares.  The formula is set forth in full in the applicable award agreement.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/  W. Thaddeus Miller, Attorney-in-Fact</signatureName>
        <signatureDate>2010-08-13</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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