<SEC-DOCUMENT>0001140361-15-009755.txt : 20150302
<SEC-HEADER>0001140361-15-009755.hdr.sgml : 20150302
<ACCEPTANCE-DATETIME>20150302182203
ACCESSION NUMBER:		0001140361-15-009755
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20150226
FILED AS OF DATE:		20150302
DATE AS OF CHANGE:		20150302

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:		7138302000

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

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			PRUETT STEVEN D
		CENTRAL INDEX KEY:			0001606682

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-12079
		FILM NUMBER:		15666435

	MAIL ADDRESS:	
		STREET 1:		717 TEXAS AVENUE 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>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2015-02-26</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001606682</rptOwnerCik>
            <rptOwnerName>PRUETT STEVEN D</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>CALPINE CORPORAITON</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, Commercial Ops</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, par value $0.001 per share</value>
            </securityTitle>
            <transactionDate>
                <value>2015-02-26</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>2883</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>21.46</value>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>62848</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, par value $0.001 per share</value>
            </securityTitle>
            <transactionDate>
                <value>2015-02-28</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>4305</value>
                    <footnoteId id="F3"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>21.20</value>
                    <footnoteId id="F4"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>58543</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Represents shares withheld by Calpine Corporation (the &quot;Company&quot;), at the reporting person's request, as permitted under the Calpine Corporation 2008 Equity Incentive Plan (the &quot;Equity Plan&quot;), to satisfy the reporting person's tax withholding obligation in connection with the vesting on Thursday, February 26, 2015 of certain shares of restricted stock previously awarded to the reporting person. There was no open market sale of shares by the reporting person.</footnote>
        <footnote id="F2">Closing market price per share of the Company common stock on the transaction date.</footnote>
        <footnote id="F3">Represents shares withheld by the Company, at the reporting person's request, as permitted under the Equity Plan, to satisfy the reporting person's tax withholding obligation in connection with the vesting on Saturday, February 28, 2015 of certain shares of restricted stock previously awarded to the reporting person. There was no open market sale of shares by the reporting person.</footnote>
        <footnote id="F4">Closing market price of the Company common stock on Friday, February 27, 2015, representing the closing price per share on the next immediately preceding day on which the New York Stock Exchange was open for trading preceding the Saturday, February 28, 2015 vesting date, as provided under the Equity Plan.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ W. Thaddeus Miller by Power of Attorney</signatureName>
        <signatureDate>2015-03-02</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
