Geothermal Heat Pumps Cut Bills and Emissions

About six million people in the U.S. get energy from geothermal applications—nearly half from geothermal plants in the West, and the other half from direct-use and geothermal heat pumps. Also known as ground-source heat pumps (GSHPs), geothermal heat pumps use a similar concept as geothermal power plants, only on a much smaller scale.

Because the upper 10 feet of the earth maintains an almost constant temperature between 50° and 60°F (10°-16°C), the pumps exchange air with the ground to heat and cool buildings.

During installation, 200-300-foot holes are drilled into the yard and pipes are inserted vertically, or pipe is laid out horizontally about six feet under the ground. Water is circulated through the pipes, and is exchanged in a heat pump about the size of a medium refrigerator inside the house.

Though the initial cost of installation is sometimes two to three times greater than that of an electric heat pump, the savings in electricity brings a payback of three to eight years (two to three years for commercial buildings). Thereafter, homeowners will enjoy a 25%-65% reduction in heating and cooling electricity costs for the life of the system—about 25 years for the unit and 50 years for the ground loop. There is a positive cash flow, since the energy savings usually exceed payment on the system, according to the International Ground Source Heat Pump Association (IGSHP).

Demand for Geothermal Heat Pumps Is Growing

Ground-source heat pumps only use electricity to move heat, not produce it, so a GSHP typically supplies four to five kilowatts of heat for every kilowatt of electricity used. Three to four of these kilowatts of heat come directly from the earth itself, and are clean, free and renewable. According to the IGSHP, these heat pumps also minimize ozone layer destruction by using factory-sealed refrigeration systems, which will seldom if ever have to be recharged. And because the system doesn't rely on outside air, it keeps a home's inside air cleaner and free from pollens, outdoor pollutants, mold spores and other allergens.

Demand for geothermal heat pumps is increasing at a rate of about 20% per year, according to the Geo-Heat Center at the Oregon Institute of Technology. That kind of growth is about all the industry can handle for now: A recent New York Times article brought to light the struggle the industry is having in keeping up with demand for the machinery, contractors, drillers and other trained workers.

For Houses Old and New

A geothermal heat pump makes sense for a new home, since the cost of the heat pump is figured into the mortgage. Homeowners who are planning to retrofit their homes with renewable energy often first think of solar, but a geothermal heat pump may be a better first choice, says Brian Henderson of Envinity, Inc., a green design and construction company in State College, Pennsylvania. Geothermal heat pumps can take care of about half of the hot water needs of a household, as well as dehumidifying the home, so once the GSHP is up and running (which it does very quietly), it's easier to get an idea of how much solar would be needed to take care of the rest of the electric load.

According to the U.S. Department of Energy, about 64% of a home's energy consumption is for heating, cooling and hot water. A GSHP might just be the answer to the vital need to conserve that energy and reduce emissions at the same time.