Tecogen Inc., together with its subsidiaries, designs, manufactures, markets, and maintains ultra-clean cogeneration products for multi-family residential, commercial, recreational and industrial use in the United States and internationally. It operates through three segments: Products, Services, and Energy Production. The Products segment designs, manufactures, and sells industrial and commercial cogeneration systems. Its Services segment provides operations and maintenance services for products under long term service contracts. The Energy Production segment sells energy in the form of electricity, heat, hot water, and cooling to customers. The company also offers natural gas-powered cogeneration systems, chillers, and heat pumps products for water and space heating, and 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 chillers, and hybrid-drive air-cooled and gas engine-driven chillers to produce chilled water and hot water; Tecofrost, a gas engine-driven refrigeration compressors to circulate refrigerant and provide hot water as a byproduct; and Ultera, an emissions control technology. In addition, the company provides long-term maintenance contracts, parts sales, and turnkey installation for products through a network of field service centers. The company sells its products to healthcare, housing and hospitality, education and government, industrial, agriculture, and breweries markets through in-house marketing, as well as independent sales agents and representatives. Tecogen Inc. was incorporated in 2000 and is headquartered in Waltham, Massachusetts.