Comfort Systems USA has paid $2.8 million to acquire the $25 million mechanical contracting firm Granite State Plumbing & Heating from KeySpan Corp., a New York-based natural gas and electric utility. The price was based on the tangible value of Granite's net assets. KeySpan has become the latest utility company to exit the mechanical services business following the wave of buyouts in the late 1990s. Comfort Systems, itself created during the wave of industry consolidation, now operates 61 locations.