Comfort Systems USA, Inc. provides mechanical and electrical contracting services. The Company operates through two segments: Mechanical and Electrical. The Mechanical segment principally includes heating, ventilation and air conditioning (HVAC), plumbing, piping and controls, as well as off-site construction, monitoring and fire protection. This segment also installs connecting and distribution elements, such as piping and ducting. The Electrical segment includes installation and servicing of electrical systems. The Company builds, installs, maintains, repairs and replaces mechanical, electrical and plumbing (MEP) systems throughout its approximately 44 operating units at 172 locations across the United States. It is also engaged in offering engineering, design-assist and turnkey, direct hire construction services of modular systems serving the advanced technology, power and industrial sectors. It also provides mechanical construction services to the commercial and industrial sectors.