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<?xml version="1.0" encoding="windows-1252"?> |
<ownershipDocument> |
| <schemaVersion> X0306 </schemaVersion> |
| <documentType> 4 </documentType> |
| <periodOfReport> 2022-05-09 </periodOfReport> |
| <notSubjectToSection16> 0 </notSubjectToSection16> |
| <issuer> |
| | <issuerCik> 0001093691 </issuerCik> |
| | <issuerName> PLUG POWER INC </issuerName> |
| | <issuerTradingSymbol> PLUG </issuerTradingSymbol> |
| | </issuer> |
| <reportingOwner> |
| | <reportingOwnerId> |
| | | <rptOwnerCik> 0001775802 </rptOwnerCik> |
| | | <rptOwnerName> Shrestha Sanjay K </rptOwnerName> |
| | | </reportingOwnerId> |
| | <reportingOwnerAddress> |
| | | <rptOwnerStreet1> C/O PLUG POWER INC. </rptOwnerStreet1> |
| | | <rptOwnerStreet2> 968 ALBANY SHAKER ROAD </rptOwnerStreet2> |
| | | <rptOwnerCity> LATHAM </rptOwnerCity> |
| | | <rptOwnerState> NY </rptOwnerState> |
| | | <rptOwnerZipCode> 12110 </rptOwnerZipCode> |
| | | <rptOwnerStateDescription></rptOwnerStateDescription> |
| | | </reportingOwnerAddress> |
| | <reportingOwnerRelationship> |
| | | <isDirector> 0 </isDirector> |
| | | <isOfficer> 1 </isOfficer> |
| | | <isTenPercentOwner> 0 </isTenPercentOwner> |
| | | <isOther> 0 </isOther> |
| | | <officerTitle> CSO & GM, Energy Solutions </officerTitle> |
| | | <otherText></otherText> |
| | | </reportingOwnerRelationship> |
| | </reportingOwner> |
| <nonDerivativeTable> |
| | <nonDerivativeTransaction> |
| | | <securityTitle> |
| <value> Common Stock </value> |
| </securityTitle> |
| | | <transactionDate> |
| <value> 2022-05-09 </value> |
| </transactionDate> |
| | | <deemedExecutionDate></deemedExecutionDate> |
| | | <transactionCoding> |
| <transactionFormType> 4 </transactionFormType> |
| <transactionCode> F </transactionCode> |
| <equitySwapInvolved> 0 </equitySwapInvolved> |
| <footnoteId id="F1"/> |
| <footnoteId id="F2"/> |
| </transactionCoding> |
| | | <transactionTimeliness></transactionTimeliness> |
| | | <transactionAmounts> |
| <transactionShares> |
| <value> 20000 </value> |
| </transactionShares> |
| <transactionPricePerShare> |
| <value> 19.41 </value> |
| <footnoteId id="F3"/> |
| </transactionPricePerShare> |
| <transactionAcquiredDisposedCode> |
| <value> D </value> |
| </transactionAcquiredDisposedCode> |
| </transactionAmounts> |
| | | <postTransactionAmounts> |
| <sharesOwnedFollowingTransaction> |
| <value> 243146 </value> |
| <footnoteId id="F4"/> |
| </sharesOwnedFollowingTransaction> |
| </postTransactionAmounts> |
| | | <ownershipNature> |
| <directOrIndirectOwnership> |
| <value> D </value> |
| </directOrIndirectOwnership> |
| </ownershipNature> |
| | | </nonDerivativeTransaction> |
| | <nonDerivativeTransaction> |
| | | <securityTitle> |
| <value> Common Stock </value> |
| </securityTitle> |
| | | <transactionDate> |
| <value> 2022-09-28 </value> |
| </transactionDate> |
| | | <deemedExecutionDate></deemedExecutionDate> |
| | | <transactionCoding> |
| <transactionFormType> 4 </transactionFormType> |
| <transactionCode> F </transactionCode> |
| <equitySwapInvolved> 0 </equitySwapInvolved> |
| <footnoteId id="F1"/> |
| </transactionCoding> |
| | | <transactionTimeliness></transactionTimeliness> |
| | | <transactionAmounts> |
| <transactionShares> |
| <value> 45113 </value> |
| </transactionShares> |
| <transactionPricePerShare> |
| <value> 21.85 </value> |
| <footnoteId id="F5"/> |
| </transactionPricePerShare> |
| <transactionAcquiredDisposedCode> |
| <value> D </value> |
| </transactionAcquiredDisposedCode> |
| </transactionAmounts> |
| | | <postTransactionAmounts> |
| <sharesOwnedFollowingTransaction> |
| <value> 198033 </value> |
| </sharesOwnedFollowingTransaction> |
| </postTransactionAmounts> |
| | | <ownershipNature> |
| <directOrIndirectOwnership> |
| <value> D </value> |
| </directOrIndirectOwnership> |
| </ownershipNature> |
| | | </nonDerivativeTransaction> |
| | <nonDerivativeHolding> |
| | | <securityTitle> |
| <value> Common Stock </value> |
| </securityTitle> |
| | | <postTransactionAmounts> |
| <sharesOwnedFollowingTransaction> |
| <value> 6485 </value> |
| </sharesOwnedFollowingTransaction> |
| </postTransactionAmounts> |
| | | <ownershipNature> |
| <directOrIndirectOwnership> |
| <value> I </value> |
| </directOrIndirectOwnership> |
| <natureOfOwnership> |
| <value> 401(k) Plan </value> |
| <footnoteId id="F6"/> |
| </natureOfOwnership> |
| </ownershipNature> |
| | | </nonDerivativeHolding> |
| | </nonDerivativeTable> |
| <footnotes> |
| | <footnote id="F1"> Tendered to Issuer to satisfy tax withholding obligations of the Reporting Person incurred in connection with the vesting of the Reporting Person's restricted stock award. </footnote> |
| | <footnote id="F2"> The initial grant of the restricted stock award was reported on a Form 4 filed on August 21, 2019, but was inadvertently disclosed as a restricted stock unit award instead of a restricted stock award. </footnote> |
| | <footnote id="F3"> Pursuant to the Plug Power Inc. Third Amended and Restated 2011 Stock Option and Incentive Plan, each share was tendered to Issuer at the price per share on the closing date of May 6, 2022, which is the date prior to the date withholding was effected. </footnote> |
| | <footnote id="F4"> The total Amount of Securities Beneficially Owned in Table I, Column 5 reflects the addition of 50,000 shares of the restricted stock award that was previously inadvertently reported on Table II as part of a grant of 150,000 restricted stock units on the Form 4 filed on May 13, 2019. </footnote> |
| | <footnote id="F5"> Pursuant to the Plug Power Inc. Third Amended and Restated 2011 Stock Option and Incentive Plan, each share was tendered to Issuer at the price per share on the closing date of September 27, 2022, which is the date prior to the date withholding was effected. </footnote> |
| | <footnote id="F6"> The Reporting Person holds 6,485 shares of common stock in Plug Power Inc.'s 401(k) plan. The information in this report is based on a plan statement as of November 14, 2022. </footnote> |
| | </footnotes> |
| <ownerSignature> |
| | <signatureName> /s/ Gerard L. Conway, Jr., Attorney-in-Fact </signatureName> |
| | <signatureDate> 2022-12-02 </signatureDate> |
| | </ownerSignature> |
| </ownershipDocument> |