AAON, Inc. engages in the engineering, manufacturing, marketing and sale of air conditioning and heating equipment. It operates through the following segments: Units, Parts-External, Parts-Internal, and Other. Its products include air handling units, self contained units, packaged rooftop units, geothermal heat units, controls, and coils. The company was founded by Norman H. Asbjornson on August 18, 1987 and is headquartered in Tulsa, OK.

Lennox International, Inc. engages in the design, manufacture, and marketing of products for heating, ventilation, air conditioning, and refrigeration. It operates through the following segments: Home Comfort Solutions, Building Climate Solutions, and Corporate and Other. The Home Comfort Solutions segment is involved in furnaces, air conditioners, heat pumps, packaged heating and cooling systems, indoor air quality equipment, comfort control products, replacement parts, and supplies. The Building Climate Solutions segment consists of unitary heating and air conditioning equipment, applied systems, controls, installation and service of commercial heating and cooling equipment, variable refrigerant flow commercial products, curb, curb adapters, drop box diffusers, HVAC recycling and salvage service, condensing units, unit coolers, fluid coolers, air cooled condensers, air handlers, process chillers, controls, and compressor racks. The Corporate and Other segment refers to the unitary heating and air conditioning equipment, chillers, air handlers, fan coils, fluid coolers, and compressor racks. The company was founded by Dave Lennox in 1895 and is headquartered in Richardson, TX.

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 North Billerica, MA.