8-K

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

__________________________

FORM 8-K

CURRENT REPORT

PURSUANT TO SECTION 13 OR 15(d) OF THE

SECURITIES EXCHANGE ACT OF 1934

Date of report (Date of earliest event reported): April 8, 2026

TECOGEN INC.

(Exact Name of Registrant as Specified in Charter)

Delaware

(State or Other Jurisdiction of Incorporation)

001-36103	04-3536131
(Commission File Number)	(IRS Employer Identification No.)

76 Treble Cove Road, Building 1

North Billerica, Massachusetts 01862

(Address of Principal Executive Offices and Zip Code)

(781) 466-6400

(Registrant's telephone number, including area code)

Securities registered or to be registered pursuant to Section 12(b) of the Act.

Title of each class	Trading Symbol	Name of exchange on which registered
Common Stock, $0.001 par value per share	TGEN	NYSE American, LLC

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. o

Item 8.01. Other Events.

On April 8, 2026, Tecogen Inc., a Delaware corporation (the “Company”) agreed to extend the term of the Advisory Agreement dated January 18, 2018, as amended on July 22, 2019 and July 19, 2023, between the Company and Mr. John N. Hatsopoulos (the “Advisory Agreement”) through March 31, 2028. The extension of the term of the Advisory Agreement was approved by Unanimous Written Consent of the Company’s Board of Directors on April 7, 2026. A copy of the letter agreement extending the Advisory Agreement is attached hereto as Exhibit 99.1.

Item 9.01. Financial Statements and Exhibits.

(d) Exhibits

Exhibit	Description
99.1	Letter Agreement dated April 8, 2026 extending the term of the Advisory Agreement between Tecogen Inc. and John N. Hatsopoulos.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the Company has duly caused this report to be signed on its behalf by the undersigned, hereunto duly authorized.

	TECOGEN INC.
		By: /s/ Abinand Rangesh
April 8, 2026		Abinand Rangesh, Chief Executive Officer

EX-99.1

XML

Cover	May 09, 2024
Cover [Abstract]
Document Type	8-K
Document Period End Date	Apr. 08, 2026
Entity Registrant Name	TECOGEN INC.
Entity Incorporation, State or Country Code	DE
Entity File Number	001-36103
Entity Tax Identification Number	04-3536131
Entity Address, Address Line One	76 Treble Cove Road, Building 1
Entity Address, State or Province	MA
Entity Address, City or Town	North Billerica
Entity Address, Postal Zip Code	01862
City Area Code	781
Local Phone Number	466-6400
Written Communications	false
Soliciting Material	false
Pre-commencement Tender Offer	false
Pre-commencement Issuer Tender Offer	false
Entity Emerging Growth Company	false
Amendment Flag	false
Entity Central Index Key	0001537435