Tecogen Inc. designs, manufactures, markets, and maintains industrial and commercial cogeneration systems that produce combinations of electricity, hot water, and air conditioning for residential, commercial, recreational, and industrial use in the United States and internationally. It operates in two segments, Products and Services, and Energy Production. The company offers InVerde e+, a cogeneration product that provides electricity and hot water; TECOGEN cogeneration systems for producing hot water; TECOCHILL air-conditioning and refrigeration chillers; and water heaters under the Ilios brand name, as well as emissions control technology under the Ultera brand name. It also provides long-term maintenance contracts, parts sales, and turnkey installation services through a network of 10 field service centers in California, the Midwest, the Northeast, and the Southeast. In addition, the company installs, owns, operates, and maintains distributed generation and other complementary systems. It serves hospitals and nursing homes, colleges 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, military installations, and indoor growing facilities. The company was incorporated in 2000 and is headquartered in Waltham, Massachusetts.