Our church installed a geothermal heat pump. The contractor told me they are the most efficient, comfortable way to air-condition and heat homes. Would one be a good choice for my 2,000-square-foot home and do I need a large yard?—Kyle N.
Although the contractor is correct about the efficiency of geothermal heat pumps, one can never be sure if a heating or cooling system provides the best payback without having a detailed analysis done for your home. For example, if your house is very energy efficient and already has low utility bills, then even cutting those small bills in half will not result in a huge savings in dollars, even though the percentage reduction is large.
But you can also consider other factors. By using less electricity with a geothermal system, there are fewer emissions from generating plants and our resources will last longer. It also reduces the peak summer electric load for your electric co-op, which reduces the need for long-term rate increases.
The U.S. Environmental Protection Agency has analyzed six cities of very different climates and found that geothermal heat pumps produce the lowest year-round utility bills of any central heating/ cooling system. Other advantages are high durability and low maintenance. Since outdoor air is not needed with a geothermal heat pump, the noisy outdoor condenser unit is not needed.
To give you an idea of how efficient geothermal heat pumps are, an older central air conditioner may have an efficiency rating of 8. The most efficient geothermal heat pumps have efficiencies as high as 27. If it now costs you $300 a month to cool your house, your monthly cooling electric bills would be cut to less than $100.
Almost every geothermal heat pump offers an optional built-in desuperheater. During the summer, any heat pump or central air conditioner draws heat from the air inside your house and transfers it outdoors. Instead, a desuperheater diverts this heat drawn from inside your house to your water heater for basically free hot water. With a large family, this can save another $100 per month for water heating.
Geothermal heat pumps produce their super-high efficiency because they use the huge thermal mass of the earth instead of the outdoor air. During the winter, the ground temperature stays warmer than the outdoor air, so it is easier for the geothermal heat pump to draw heat into your home. During the summer, the ground stays cooler than the outdoor air, so the geothermal heat pump can dump the heat more efficiently.
The cost of installing a typical 3-ton (36,000 Btu) geothermal heat pump will cost several thousand dollars more than installing a gas furnace and a central air conditioner. The geothermal heat pump will often pay back the higher initial cost in about eight years or less, depending on local utility rates. Geothermal heat pumps typically have a life of 20 years or more.
You don’t need a large yard for a geothermal heat pump. There are two designs of geothermal heat pumps. One type uses a polyethylene pipe ground loop either in a horizontal trench or vertical holes (requires less space) in your yard. A water/antifreeze solution runs through the pipes, which are connected to the unit inside your home.
The other design (called DX) uses small copper tubes buried in the ground and the refrigerant flows directly through them. The heat exchanger is not needed. With this direct heat exchanging with the ground, less tubing is needed. This is often ideal for smaller yards.
Write for Utility Bills Update No. 924, a buyer’s guide of 14 geothermal heat pump manufacturers. Include $3.00, a business-size SASE, and Update number. Mail requests and questions to James Dulley, Kentucky Living, 6906 Royalgreen Drive, Cincinnati, OH 45244. Go to www.dulley.com to instantly download.