Tecogen, Inc. engages in the production of commercial and industrial, natural-gas-fueled engine-driven, and combined heat and power (CHP) products. It operates through the Products, Services, and Energy Production segments. The Products segment designs, manufactures, and retails industrial and commercial cogeneration systems. The Services segment installs and maintains the cogeneration systems. The Energy Production segment sells energy in the form of electricity, heat, hot water, and cooling to customers under long-term sales agreements. The company was founded by George N. Hatsopoulos and John N. Hatsopoulos in 1987 and is headquartered in Waltham, MA.