New York Still Runs the World's Largest Steam Heating System
About 1,500 Manhattan customers buy steam by the pipe, and some use it to run air conditioning.
Practical Engineering · What's Under Your Feet in New York City?New York City still runs the world's largest steam heating system, by far. About 1,500 customers buy steam as a public utility, delivered through underground pipes concentrated in Manhattan.
Most use it the obvious way, for heating buildings and hot water. But the same pipes also sterilize equipment in hospitals, clean dishes in restaurants, and run the presses in dry cleaning shops.
Most counterintuitively, the steam can even cool buildings in summer, by powering steam-driven compressors for air conditioning. A winter utility becomes a summer one.
Questions people ask
Where does all that steam come from?
Mostly from Con Edison power plants in and around Manhattan, including cogeneration plants that make electricity and capture the leftover heat as steam. The steam is then sent out through insulated underground mains at high pressure. Customers are metered much like they are for electricity or water.
How can steam possibly run air conditioning?
Heat can drive cooling through machines called absorption chillers, which use thermal energy instead of an electric motor to run a refrigeration cycle. Other buildings use steam turbines to spin conventional compressors. Either way, the same summer steam that heats hot water can make cold air.
Why only Manhattan?
District steam makes economic sense only where many large buildings sit close together, so one set of pipes can serve many paying customers. Manhattan has that density, plus a system built out over more than a century. In lower density boroughs, individual boilers and furnaces are cheaper to install and maintain.