Tecogen Inc. Advisory Agreement Extension

Tecogen Inc. has extended the term of its Advisory Agreement with Mr. John N. Hatsopoulos. The agreement, originally dated January 18, 2018, and previously amended, will now run through March 31, 2028. This extension was approved by the Company’s Board of Directors on April 7, 2026. A letter agreement detailing the extension, dated April 8, 2026, has been filed as an exhibit.