Tecogen Inc., together with its subsidiaries, designs, manufactures, markets, and maintains cogeneration products for multi-family residential, commercial, recreational, and industrial use in the United States. It operates in three segments: Products, Services, and Energy Production. The Products segment designs, manufactures, and sells industrial and commercial cogeneration systems to hospitals and nursing homes, schools and universities, health clubs and spas, hotels and motels, office and retail buildings, food and beverage processors, multi-unit residential buildings, laundries, ice rinks, swimming pools, factories, municipal buildings, indoor agriculture, military installations, and indoor growing facilities. Its Services segment provides operations and maintenance services for its products under long term service contracts. The Energy Production segment installs, operates, and maintains distributed own generation electricity systems and sells the energy generated by such systems in the form of electricity, heat, hot water, and cooling to its customers under long-term energy sales agreements. The company also offers natural gas-powered cogeneration systems for water and space heating, and/or air conditioning. Its product portfolio includes InVerde e+ and TecoPower cogeneration units for the supply electricity and hot water; Tecochill, an air-conditioning and refrigeration chiller, and hybrid-drive air-cooled and gas engine-driven chiller to produce chilled water and hot water; Tecofrost, a gas engine-driven refrigeration compressor to circulate refrigerant and provide hot water as a byproduct; and Ultera, an emissions control technology. It sells its products through in-house marketing, as well as independent sales agents and representatives. Tecogen Inc. was incorporated in 2000 and is headquartered in North Billerica, Massachusetts.