Is Geothermal The Way To Go?

A Reader Asks The Green Guide:

We're beginning to work on a remodel for our house. We currently heat with wood (this is a very old house...no ducting, etc.) We have been told we have to install some kind of heating system for the addition and that electric systems (such as radiant floor) are not an option in this county. We don't want to go with gas if we can avoid it. Passive Solar is not an option (sigh).

What do you know about geothermal heat pump systems? We live in the country on acreage, near the coast of Central California. Average winter low's in the low 20's; summer high's in the 90's +. We've done fine with wood heat, but we're getting older and should consider an "easier" heat source. Thanks for any advice you can offer.

Janita Baker

The Green Guide Responds:

Geothermal heat pumps (GHPs) are an extremely efficient mode of not only heating your home in the winter but cooling it in the summer. The technology exploits the difference between above ground and below ground temperatures. Ground temperatures range from 45 degrees to 75 degrees Fahrenheit and remain relatively constant throughout the year. The open air temperature is cooler than the ground temperature during the winter and warmer during the summer. Using a system of underground or underwater pipes filled with a coolant—like antifreeze—the GHP exchanges the heat above ground with the heat below ground. Operating on the same principal as a refrigerator, the heat, carried by piped water and coolant, is elevated through a process of compression, evaporation, condensation and expansion. This process requires substantial electricity, though far less than an electric heating system requires. Within the heat pump, liquid refrigerant absorbs heat from the warmed water or other low temperature source as it flows from the ground, which causes the refrigerant to evaporate and become gaseous. The gas is then pressurized in an electric compressor. This raises the temperature to 180+ degrees Fahrenheit. The heat is pumped into the house, and as the refrigerant cools, the process begins all over again.

Advantages

• Compared with a home with electric heat, cooling, and water heating, the GHPs use between to 25% and 50% less electricity. According to the Department of Energy (DOE), a housing project in Louisiana with 4003 units will save 25.8 million kilowatt hours in a typical year after switching to GHP. EnergyStar-rated pumps are also available. www.eere.energy.gov/consumerinfo/factsheets/geo_heatpumps.html

• During the summer GHP (equipped with a device called a "desuperheater") using heat taken from the home will warm your water for free. During the winter, you can expect a 50% reduction in the cost of heating water.

• GHPs are smaller and quieter than gas and oil furnaces.

• New homes may come equipped with GHP, but older homes can be retrofit as well. Obviously efficiency is an issue in either case, and for the full benefit to be realized, ducting and insulation must be properly installed. And the house must be thoroughly weather proofed.

• GHP systems have few moving parts and require very little maintenance.

• Switching to a GHP system is cost effective. Installing a system will cost approximately $7,500, where a comparable conventional system (heat and cooling) costs around $4,000, but, according to the Department of Energy, the savings from lower untility bills, will pay for the difference in two to ten years.

Disadvantages

• The initial cost is quite high.

• Leaks in underground pipes are hard to repair.

• Water is a better heat source than earth, but water-coupled systems require a body of water, more complex engineering and the built-in cost of a water pump.

For more information about GHP systems and a list of certified service providers in California visit the Geothermal Heat Pump Consortium website (www.geoexchange.org). Many states offer incentive programs, but surprisingly not California. EnergyStar labeled models are usually eligible for low interest loans. The EPA has more information about financing, and they encourage home owners to call their free hotline: 1-888-STAR-YES

Given that you're currently using wood heat, another option would be to trade in your old stove for a super-efficient advanced combustion wood burning stove. (See "Is Burning Wood Greener Than Burning Gas?")