Comfort Systems USA, Inc. is an American company that provides mechanical and electrical contracting services, primarily HVAC, plumbing, piping and controls, off-site construction, monitoring and fire protection, and installation and servicing of electrical systems. The company is registered in Delaware and headquartered in Houston, Texas. It has 47 operating units with 178 locations in 136 cities in the United States. It is ranked 520th on the Fortune 500. In 2024, the company was ranked 6th by Engineering News-Record on its list of the top 600 specialty contractors. In 2024, 56.7% of revenue was from installation services in newly constructed facilities and 43.3% was from renovation, expansion, maintenance, repair and replacement services in existing buildings.