Geothermal heat pumps, used to heat and cool buildings and provide domestic hot water, have been around since the 1930s. Why are they only now becoming popular? According to Carl Orio of Water and Energy Systems in Atkinson, N.H., who has sold and designed geothermal heat pumps for 25 years, cost and the fact that the technology crosses trades (it involves both well-drillers and electricians) gave the pumps a "nonconventional" label for many years. Rising fuel costs, increased promotion, and an upsurge of interest in environmental building have contributed to a marked increase in sales.
Geothermal heat pumps move heat from the earth to the building (or from building to earth, when used for air conditioning). In the most popular system, ground water is pumped from a well to a series of compressors. These compressors, which contain sealed coils filled with refrigerant, extract the heat from the water; this solution is then used to heat the building.
Morton Eagle has had four heat pumps in his house for more than six years. ("It's a big house," he explains - the average house requires only one.) He particularly likes the safe, clean, and comfortable heat they provide. Would he recommend one? Mr. Eagle answers with an emphatic "yes." "We've recouped our money many times."
According to Mr. Orio, the equipment for a geothermal heat pump costs about the same as a high-efficiency oil or gas heat and air-conditioning system; it's the installation that can raise the price - anywhere from a few hundred to several thousand dollars (it's cheapest where there's an existing well).
The savings comes in lower operating costs - perhaps only half as much as conventional systems. According to the United States Environmental Protection Agency, geothermal heat pumps are the most efficient space-conditioning technology available; they also have the lowest carbon-dioxide emissions.
The heat pumps are not completely "green" since they run on electricity and some pollution results from the generation of power. Some people are also concerned about hazards from the refrigerant used.
Across the country, public agencies, utilities, and private organizations are strongly promoting the technology. Many utility companies offer incentive programs to reduce the cost of the pumps to consumers, and the International Ground Source Heat Pump Association, in Stillwater, Okla., provides professional training and public information. In 1994, the Department of Energy and the Environmental Protection Agency joined with power utilities to form the Geothermal Heat Pump Consortium in Washington, D.C. There are an estimated 250,000 geothermal heat pumps in residential and commercial use in the US.