<SUBMISSION>
<ACCESSION-NUMBER>0001181431-03-021866
<TYPE>4
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20030904
<FILING-DATE>20030904
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>COOPER JOHN R
<CIK>0001168815
<STATE-OF-INCORPORATION>DE
<FISCAL-YEAR-END>1130
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>4
<ACT>34
<FILE-NUMBER>000-15472
<FILM-NUMBER>03881581
</FILING-VALUES>
<BUSINESS-ADDRESS>
<STREET1>C/O ENVIRONMENTAL POWER CORP
<STREET2>ONE CATE ST
<CITY>PORTSMOUTH
<STATE>NH
<ZIP>03801
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>C/O ENVIRONMENTAL POWER CORP
<STREET2>ONE CATE ST
<CITY>PORTSMOUTH
<STATE>NH
<ZIP>03801
</MAIL-ADDRESS>
</REPORTING-OWNER>
<ISSUER>
<COMPANY-DATA>
<CONFORMED-NAME>ENVIRONMENTAL POWER CORP
<CIK>0000805012
<ASSIGNED-SIC>4991
<IRS-NUMBER>042782065
<STATE-OF-INCORPORATION>DE
<FISCAL-YEAR-END>1231
</COMPANY-DATA>
<BUSINESS-ADDRESS>
<STREET1>500 MARKET ST
<STREET2>STE 1E
<CITY>PORTSMOUTH
<STATE>NH
<ZIP>03801
<PHONE>6034311780
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>500 MARKET ST
<STREET2>STE 1E
<CITY>PORTSMOUTH
<STATE>NH
<ZIP>03801
</MAIL-ADDRESS>
</ISSUER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>rrd17806.xml
<TEXT>
<XML>
<?xml version="1.0"?><ownershipDocument>
    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType><periodOfReport>2003-09-04</periodOfReport><notSubjectToSection16>0</notSubjectToSection16>
    <issuer>
        <issuerCik>0000805012</issuerCik>
        <issuerName>ENVIRONMENTAL POWER CORP</issuerName>
        <issuerTradingSymbol>( powr )</issuerTradingSymbol></issuer><reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001168815</rptOwnerCik>
            <rptOwnerName>COOPER JOHN R</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O ENVIRONMENTAL POWER CORP.</rptOwnerStreet1>
            <rptOwnerStreet2>ONE CATE STREET 4TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>PORTSMOUTH</rptOwnerCity>
            <rptOwnerState>NH</rptOwnerState>
            <rptOwnerZipCode>03801</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>1</isDirector><isOfficer>0</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther></reportingOwnerRelationship></reportingOwner><derivativeTable><derivativeTransaction><securityTitle><value>2002 Director Options (right to buy)</value></securityTitle><conversionOrExercisePrice><value>.66</value></conversionOrExercisePrice><transactionDate><value>2003-08-06</value></transactionDate><deemedExecutionDate><value>2003-08-06</value></deemedExecutionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>M</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>100000</value></transactionShares><transactionPricePerShare><value>.66</value></transactionPricePerShare><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><exerciseDate><value>2003-08-06</value></exerciseDate><expirationDate><value>2013-08-06</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common</value></underlyingSecurityTitle><underlyingSecurityShares><value>100000</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>100000</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership></ownershipNature></derivativeTransaction></derivativeTable><ownerSignature><signatureName>/s/ John R. Cooper</signatureName><signatureDate>2003-09-04</signatureDate></ownerSignature></ownershipDocument>



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