<SEC-DOCUMENT>0001537435-17-000083.txt : 20170601
<SEC-HEADER>0001537435-17-000083.hdr.sgml : 20170601
<ACCEPTANCE-DATETIME>20170601164653
ACCESSION NUMBER:		0001537435-17-000083
CONFORMED SUBMISSION TYPE:	3
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20170523
FILED AS OF DATE:		20170601
DATE AS OF CHANGE:		20170601

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			TECOGEN INC.
		CENTRAL INDEX KEY:			0001537435
		STANDARD INDUSTRIAL CLASSIFICATION:	AIR COND & WARM AIR HEATING EQUIP & COMM & INDL REFRIG EQUIP [3585]
		IRS NUMBER:				043536131
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		45 FIRST AVENUE
		CITY:			WALTHAM
		STATE:			MA
		ZIP:			02451
		BUSINESS PHONE:		781-466-6400

	MAIL ADDRESS:	
		STREET 1:		45 FIRST AVENUE
		CITY:			WALTHAM
		STATE:			MA
		ZIP:			02451

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	TECOGEN INC
		DATE OF NAME CHANGE:	20111215

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			BROWN BONNIE JEAN
		CENTRAL INDEX KEY:			0001585816

	FILING VALUES:
		FORM TYPE:		3
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-36103
		FILM NUMBER:		17885323

	MAIL ADDRESS:	
		STREET 1:		97 FIFTY ACRE WAY
		CITY:			CARLISLE
		STATE:			MA
		ZIP:			01741
</SEC-HEADER>
<DOCUMENT>
<TYPE>3
<SEQUENCE>1
<FILENAME>wf-form3_149634999664481.xml
<DESCRIPTION>FORM 3
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0206</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2017-05-23</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0001537435</issuerCik>
        <issuerName>TECOGEN INC.</issuerName>
        <issuerTradingSymbol>TGEN</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001585816</rptOwnerCik>
            <rptOwnerName>BROWN BONNIE JEAN</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O TECOGEN INC.</rptOwnerStreet1>
            <rptOwnerStreet2>45 FIRST AVENUE</rptOwnerStreet2>
            <rptOwnerCity>WALTHAM</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02451</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Chief Accounting Officer</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1762</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Option (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>3.15</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2025-09-02</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>9200.0</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Following the completion of the Merger and pursuant to the Merger Agreement between American DG Energy and the Company dated November 1, 2016 and as amended March 23, 2017, American DG Energy's securities were converted to securities of the Company.</footnote>
    </footnotes>

    <remarks>This transaction is exempt from liability under Section 16(b) of the Securities Exchange Act of 1934.</remarks>

    <ownerSignature>
        <signatureName>/s/ Bonnie Brown</signatureName>
        <signatureDate>2017-06-01</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
