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Drawbacks of geothermal heating systems

Geothermal, or geo-exchange, heating systems have many environmental advantages, but a few drawbacks, too.

By / November 5, 2009

Hoses are installed that will eventually be attached to the geothermal heating system for the renovation of Sheep Dog Hollow, a 1902 farmhouse in Connecticut.

Joanne Ciccarello/Staff/The Christian Science Monitor

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I’m sold on geothermal heating. Just check out my previous blog post. But being trained as a journalist, I can’t help but strive for at least some kind of balance. And so, I’ve felt it necessary to outline some of the various problems associated with geothermal residential heating.

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First, let’s start with the very basics – the word geothermal itself. Several helpful readers have noted that there’s a bit of confusion about just what it means. So let’s get that cleared up.

Geothermal, as the word is traditionally used, refers to harnessing “energy from ‘hot spots’ in the earth's crust, and can only be employed in locations where these exist,” according to the website Lighthouse.

On the other had, geoexchange, as Lighthouse notes, “uses the relatively constant temperature of the ground to simply moderate a building's temperature.

For example, in the winter, the ground temperature is usually warmer than the air temperature, so heat is pumped from the ground to help heat the building. In the summer, the opposite is the case, and the building can be cooled.”

So, technically, we’ve been talking about a geoexchange system. (I’m still sold on it, even if it does have a different name.) But, like much in the English language in America, meanings evolve and specificity sometimes gets lost.

As it turns out, the “geothermal” is now commonly used as a catchall for both traditional geothermal systems and geoexchange systems, at least according to the International School of Well Drilling.

There are two types of geothermal energy, it explains in one of its training documents [pdf]:

1. High Grade – High-grade geothermal energy is the heat of the earth’s pressure which turns water into steam. Old Faithful at Yellowstone National Park is an excellent example.
2. Low Grade – Low-grade geothermal is the heat within the earth’s crust. This heat is actually stored solar energy.
We will use the terms "low-grade geothermal" or "geothermal" throughout this presentation because it’s the most commonly used.

So, forgive me for being common, but I’m going to continue to refer to the heating system that we’ve chosen as “geothermal,” even though the technically minded are welcome to quibble with me.

Now on to some of the more pedestrian problems with a geothermal heating system:
1. First and foremost, at least from my perspective, are the high upfront costs. The internal works – the heat pump, ducts, electrical, etc., cost about the same as a top of the line, highly efficient traditional oil or gas heating system. But on top of that, you have to add the cost of drilling the wells. In our case, we’re talking an additional $20,000. But, fortunately, there are tax breaks and longterm savings to offset those drilling costs.

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