What Is Geothermal Heat Pumps?

If you’re planning to build a new house, office building, or school, or replace your heating and cooling system, you may want to consider a geothermal heat pump

(GHP) system. GHP systems are also known as GeoExchangeSM, ground-source, or water-source heat pumps (as opposed to air-source heat pumps). Regardless of

what you call them, energy-efficient geothermal heat pumps are available today for both residential and commercial building applications.

AGHP system can be installed in virtually any area of the country and will save energy and money. According to the Environmental Protection Agency (EPA), GeoExchange systems are the most energy efficient, environmentally clean, and costeffective space conditioning systems available (source: "Space Conditioning: The Next Frontier," EPA430-R-93-004, April 1993).

While residential GHP systems are usually more expensive initially to install than other heating and cooling systems, their greater efficiency means the investment can be recouped in two to ten years. After that, energy and maintenance costs are much less than conventional heating and air-conditioning systems.

When GHP systems are installed in commercial buildings, the state-of-the-art designs are extremely competitive on upfront costs when compared with cooling towers and boilers, and they have lower energy and maintenance costs.

In addition to their cost effectiveness, GHP systems offer aesthetic advantages, quiet operation, free or reduced-cost hot water, improved comfort, and a host of other benefits.

What Is a Geothermal Heat Pump?

Geothermal heat pumps are viable nationwide. They use the Earth as a heat sink in the summer and a heat source in the winter, and therefore rely on the relative warmth of the earth for their heating and cooling production.

Through a system of underground (or underwater) pipes, they transfer heat from the warmer earth or water source to the building in the winter, and take the heat from the building in the summer and discharge it into the cooler ground. Therefore, GHPs don’t create heat; they move it from one area to another.

How Do They Work?

Simply put, a GHP works much like the refrigerator in your kitchen, with the addition of a few extra valves that allow heatexchange fluid to follow two different paths: one for heating and one for cooling. The GHP takes heat from a warm area and exchanges the heat to a cooler area, and vice versa. The beauty of such a system is that it can be used for both heating and cooling—doing away with the need for separate furnace and air-conditioning systems— and for free hot water heating during the summer months.

Low Energy Use

The biggest benefit of GHPs is that they use 25-50% less electricity than conventional heating or cooling systems. This translates into a GHP using one unit of electricity to move three units of heat from the earth.

According to a report by Oak Ridge National Laboratory, statistically valid findings show that the 4,003- unit GHP retrofit project at Fort Polk, Louisiana, will save 25.8 million kilowatthours (kWh) in a typical meteorological year, or 32.5% of the pre-retrofit wholecommunity electrical consumption.

This translates to an average annual savings of 6,445 kWh per housing unit. In addition, 100% of the whole-community natural gas previously used for space conditioning and water heating (260,000 therms) will be saved. In housing units that were all-electric in the pre-retrofit period, the GHPs were found to save about 42% of the preretrofit electrical consumption for heating, cooling, and water heating.