|Geothermal heat pumps, also referred to as ground source heat pumps or geo-exchange, refer to systems that use the ground, groundwater, or surface water as a heat source or sink. Specific to their configuration, these systems are referred to as ground-coupled heat pumps, groundwater heat pumps, and surface water heat pumps, respectively. The first successful commercial project was installed in the Commonwealth Building in Portland, Oregon in 1946. As of 2004, the United States had 12 gigawatts of installed thermal capacity from geothermal heat pumps, with an additional 80,000 units installed each year.
Geothermal heat pumps use 25% to 50% less electricity than conventional heating or cooling systems. Relative to air-source heat pumps, they are quieter, last longer, need little maintenance, and do not depend on the temperature of the outside air. Considerations including utility rates for electricity, natural gas, or other fuels can impact decisions to implement this technology.
While most sites throughout the United States can utilize geothermal heat pump technologies, certain site characteristics will influence the type of system most suitable for a site. Available ground area, thermal conductivity of the surrounding soil, local ground water availability and temperatures, or access to open water sources can further direct their use in a project.
This overview is intended to provide specific details for Federal agencies considering geothermal heat pump technologies as part of a new construction project or major renovation. Further general information is available from the U.S. Department of Energy (DOE) Office of Energy Efficiency and Renewable Energy (EERE) Geothermal Heat Pump Basics.