Tecogen Inc. designs, manufactures, markets, and maintains ultra-clean cogeneration products. The Company includes natural gas engine-driven combined heat and power (CHP) systems, chillers, and heat pumps for multi-family residential, commercial, recreational, and industrial use. The Company operates through three segments: Products, Services, and Energy Production. The Products segment designs, manufactures and sells industrial and commercial cogeneration systems. The Services segment provides operations and maintenance services and turn-key installation for its products under long-term service contracts. The Energy Production segment, which installs, operates, and maintains distributed generation electricity systems that it owns and sells 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's products are sold with its patented Ultera emissions technology.