Ground-source heat pumps (AKA geothermal heat pumps or geothermal/ground heat exchangers) take air from underground, which maintains a nearly constant temperature between 50° and 60°F year-round, and deliver it above ground where it can reduce energy use by heating units and air conditioners. GSHP systems are well suited for large to mid-sized buildings because they can easily dissipate the heat, but they can also be used in residential applications.
Since 2009, the City College of San Francisco’s Balboa Reservoir has been successfully operating a ground-source heat pump. This system has 400 ground loops at 400 feet deep, providing 650 tons of cooling. Read more about this installation.