Geothermal heat pump systems: The future of home heating?

Depending on where you live, it may soon be time to get reacquainted with an old friend: your home's heating system. While your unit might be in a little better shape than the old coal furnace featured in "A Christmas Story," there's still a good chance it could be getting a bit dated.

If your heating bills seem to be increasing every year, why not upgrade to a system so efficient it may be able to cut your annual utility costs by up to 70 percent? How does it do it? A geothermal heat pump system uses the earth's temperature to help condition your home.

What you should know about geothermal heat pumps

Imagine a heating system designed to keep your home toasty on the coldest winter nights that can operate at a 300 to 600 percent efficiency rating. While it might sound like something that could be possible in the distant future, the technology has actually been in existence since the 1940s.

The air-source heat pumps found on many modern homes use the outside temperature to assist in conditioning the air being circulated throughout the structure's interior. A geothermal heat pump takes the process one step further by using the earth's core temperature. The advantage: the temperature of the earth several feet below the surface remains much more constant than what may be going on in the atmosphere at ground level.

On hot days, the soil is usually much cooler a few feet under the finish grade and the reverse is true during the winter. Anyone who has ever had to dig a hole in frozen soil knows that the shoveling gets a little easier when they get down past the frost line. A geothermal system uses this temperature difference to condition a home by utilizing a ground heat exchanger. There are a number of different types of geothermal heat pump systems, but here are three that might be best suited for residential use:

• Horizontal - This is a closed loop system that involves having two pipes buried in your yard. The pipes are normally installed at least four feet below the finished grade and may be installed side-by-side or one over the top of the other with soil separation in the same trench.
• Pond - If you have a pond on your property that meets minimum depth, volume, and quality requirements, this may be the most budget-friendly type of geothermal heat pump installation. A pipe is run from the outdoor unit to the pond where it is coiled at least eight feet below the surface and then returned to the home.
• Open loop system - This installation uses two separate pipes: one that supplies ground water to the heat pump and another that returns the used water to the soil. There must be a sufficient supply of clean water for this system to work. Local codes regarding groundwater discharge may also determine whether this system can be installed in your area.

So what's the downside? Well, a geothermal heat pump system installation can cost several times more than that of a conventional air-source unit. However, the Department of Energy estimates that the total price difference should be returned to homeowners in the form of utility cost savings within 5 to 10 years of the installation. And if you need another reason to install a geothermal unit, you could be eligible for a federal energy tax credit of up to 30 percent of the system's cost if the unit is put in by December 31, 2016.

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