SCHEDULE 13G/A 0001674697 XXXXXXXX LIVE 1 Common Stock, $0.001 par value 06/30/2025 0001537435 Tecogen Inc. 87876P201 76 Treble Cove Road Building 1 North Billerica MA 01862 Rule 13d-1(c) Tryfon Natsis and Depoina Pantopoulou, as Joint Tenants with the Right of Survivorship J3 0 460300 0 460300 460300 N 1.8 IN Percent of class represented by amount in row (9) has been calculated based on 25,269,362 shares of Tecogen Inc. common stock outstanding as of May 20, 2025, as reported in Tecogen Inc.'s prospectus on Form 424B3 filed with the Securities and Exchange Commission on May 22, 2025. Tecogen Inc. 76 Treble Cove Road, Building 1, North Billerica, Massachusetts, 01862 This statement is being filed by Tryfon Natsis and Despoina Pantopoulou, as spouses and Joint Tenants with the Right of Survivorship, as Reporting Persons. The residential address for each Reporting Person is Block 7, The St. Regis Saadiyat Island Residences, Al Saadiyat Island, 54345 Abu Dhabi, United Arab Emirates. Each Reporting Person is a citizen of Greece. Y 460,300 shares of Tecogen Inc. common stock. 1.8% (based on 25,269,362 shares of Tecogen Inc. common stock outstanding as of May 20, 2025, as reported in Tecogen Inc.'s prospectus on Form 424B3 filed with the Securities and Exchange Commission on May 22, 2025). 0 460,300 0 460,300 N Y Y Y Y Y N By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11. Tryfon Natsis and Depoina Pantopoulou, as Joint Tenants with the Right of Survivorship /s/ Tryfon Natsis 08/14/2025 /s/ Despoina Pantopoulou 08/14/2025