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Installing a Residential Geothermal Heat Pump

Mark Snyder
Do it Green! Magazine

My journey toward geothermal climate control at my home in Minneapolis began some eight years ago, after my father installed a heat pump at his house in Andover, MN.

At the time, I’ll admit I was a bit skeptical of the idea of actually being able to heat your home without burning some sort of fuel on-site such as natural gas, propane or even wood in a wood stove. This seemed especially unlikely in a climate like Minnesota’s. I later visited my dad’s house in the winter after his system was installed and found that it was actually quite comfortable. Plus, my dad got to rub my nose in the fact that I was still shelling out hundreds of dollars a month to fuel my natural gas furnace. Even better, I learned that the geothermal heat pump can also provide cooling during the summer months, so you only need one system instead of both a furnace and central air conditioning unit like many homes have. I then resolved to learn just how geothermal heating systems worked and whether it would be feasible to install such a system in my home.

Geothermal heat pumps are designed to take advantage of the fact that below the frost line, about six to eight feet deep, the Earth’s surface maintains a nearly constant temperature between 50°F and 60°F. There’s no “fuel” required beyond the electricity to run the heat pump’s compressor and blower. However, a heat pump does require an “earth loop,” which is a loop of plastic pipe that is buried in your yard that circulates a coolant solution, similar to the antifreeze in your car, to exchange heat with the ground. People with larger yards can install a horizontal loop, where the piping is laid out in trenches that are some eight to ten feet deep and a couple hundred feet long. People with smaller urban lots will need to install vertical loops, or wells. The number of wells or trenches required will depend on the design of your house. In my case, the system required four wells, each 185 feet deep, which were spaced about eight or ten feet apart. For a “virtual” demonstration online visit “How Geothermal Systems Work” (Resource Box).

When I tell people about my system, the first question they always ask is “How much did it cost?” and there’s no getting around the fact that these systems are expensive to install. My heat pump cost $10,000 plus $8,400 to install the vertical well loop. Fortunately, my dad and I were able to install the electric circuits my heat pump requires; otherwise, my installation cost might have exceeded $20,000 total. Compared to the cost of replacing my furnace and installing a central air unit, I am estimating that my payback period will be about ten years. This depends partly on how quickly natural gas prices continue to rise relative to the increased electricity my system uses; however, if recent trends continue, it’s possible I could break even in eight years or fewer.

So how do you decide if a geothermal system is right for you? Ask yourself:

  • Is my yard large enough to install an earth loop and am I willing to tear up a portion of it?
  • Am I willing and able to finance this installation? (You won’t find grants to help pay for your system and the rebates or tax incentives available will not go very far.)

If you answer “Yes” to both questions, your next step is to find the right system and installer for your home. There are a variety of geothermal heat pump manufacturers; some make smaller systems with a natural gas furnace as a back-up, while other manufacture full geothermal systems. A good starting point could be a visit to the Living Green Expo (Resource box). The Expo has featured a number of geothermal heat pump installers as well as other heating and cooling system installers. Talk to as many of them as you can, pick a few to provide estimates, and then decide what option makes the most sense for you. Good luck!

Read Up

Geothermal Heat Pumps: A Guide for Planning and Installing, by Karl Ochsner and Robin Curtis, Earthscan Publications Ltd., 2007.

 

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