How geothermal heat pumps work
A geothermal heat pump—a.k.a. geo-exchange heat pump—exploits stable temperatures that occur below ground level, typically 50°F to 65°F year-round. The “pump” moves the hot or cold air in a loop, from the earth to your house and back again.
This heat exchange happens in a “loop field,” plastic pipe buried underground either horizontally or vertically in a series of holes drilled at least 200 feet deep.
In winter, a pump circulates antifreeze fluid through the loop field where it picks up heat. Coils inside the pump extract the heat, and a fan blows this warmth through ductwork in your home. In summer, the cycle is reversed as the system extracts heat from inside a home and deposits it underground.
How a geothermal heat pump saves you money … eventually
Geothermal heat pumps are four times more efficient than 95% efficient natural gas furnaces. For every $1 you spend running a geothermal heat pump, you reap $3.80 worth of heat. “You would have to look a long time before you get a fossil-fuel rate that would be competitive with geothermal,” says Terry Munyon, a director of the Iowa Geothermal Association. “It kicks butt.”
That efficiency translates into savings—eventually. According to the U.S. Department of Energy, a geothermal heat system will save 50% to 70% of home energy usage for heating and cooling, which can amount to between $512 and $716 in your pocket every year.
However, a geothermal heat pump for a 2,000 sq. ft. house will cost about $20,000—more than twice a conventional heating and cooling system. You’ll recoup that expense in about 10 years; if you subtract what you would have spent on some other HVAC system, and consider the 30% discount you’ll get from the federal Residential Renewable Energy Tax Credit. Further deals may be available from energy utilities or your state government; check with the Database of State Incentives for Renewable Energy.
How geothermal heat makes life better … besides the money thing
- Geothermal heat pumps have few moving parts and no need for outdoor condensers.
- Geothermal heat pumps are small, so you don’t have to devote a lot of space to equipment rooms.
- Geothermal heat systems are easy to zone, so each part of your house can feel comfortable at the same time.