Geothermal Heat Pumps Tap Energy Just Below the Earth’s Surface

Geothermal heat pumps are crazy expensive to install, but they tap an unlimited supply of inexpensive heating and cooling just below the earth’s surface.

Geothermal heat pumps are uber-efficient and can shave 60% from your home heating and cooling costs. But the system, with its “loop field” of pipe extending down 200 feet, is ultra expensive to buy and install — typically $20,000 — which is twice the cost of conventional HVAC systems. If you live long enough, the investment will pay off. Here’s the drill.

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.