Solar power vs. geothermal: Which works better?

As I learn about green options as we renovate Sheep Dog Hollow, I have definitely tripped and stumbled along the way.

Alexandra Marks

Alexandra writes about the 'green' and budget-friendly renovation of a 100-year-old farmhouse in south-central Connecticut.

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Recent posts

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• 04.23.10
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In my most recent post, I noted what could have been my biggest wrong-footed move to date: choosing an expensive geothermal heating system when I could have leased a solar system for the cost of my monthly electric bill – at least, that’s how it seems on the surface.

But like all things green and cutting edge, the situation is more complex than it first appears.

Let me set the stage, though. The man from our local solar leasing company came to give a quote for our current home and was clearly taken aback when I mentioned that we had chosen geothermal for the house we’re renovating.

“Wow, that could cost you,” he said. “Your monthly electric bills could be pretty high.”

Since the geothermal system had already cost about $20,000 more than a traditional heating system, I was not pleased to hear his analysis of why it would also cost more to operate monthly than solar.

His reasoning went this way: Geothermal systems use a compressor and a heat pump to circulate the piped warm water from beneath the ground into the house and raise its temperature to a toasty 72 degrees F. That’s similar to what’s used in a central air conditioning system (but backwards and in winter.)

Since we don’t have central air conditioning, I was stunned to hear that during the summer, people who do have it can see their electric bills spike to $400 or $500 month.

“Same thing is happening with geothermal," he said. "You’re running a pump and a compressor all of the time, and you get consistently high electric bills, but for 12 months, not just during summer. So you have to be prepared for that. Some people in this area with geothermal have had $500-a-month electric bills.”

That might be true, but they’re also not paying $600 dollars a month in winter to keep their heating oil tanks full.

Nonetheless, his sales pitch got me. With the solar lease program, we could have put in a solar system for zero down. I couldn’t help but slap the palm of my hand to my head and think, “What have I done?”

(That’s especially true because my fiancé, Martin, was adamantly opposed to geothermal and I had prevailed upon him. If this was true about solar, I’d never hear the end of it.)

After the solar man left, I called Ray Sima, who had put in our geothermal wells. He and his family have been using geothermal heat here in chilly New England for the past 20 years.

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