GROUND-SOURCE HEAT PUMPS

ISABELLA O’MALLEY’S ARTICLE describes “Little-known but efficient, a different way to heat and cool your house,” AP News, July 13, 2023. It’s about ground-source heat pumps, their function related to, but differing from, conventional air-sourced devices.

Here are tidbits gleaned from O’Malley’s article together with my usual Internet sleuthing and, this time, my own first hand experience. 

Iceland’s Geothermal Heating. The term “ground-source” reminds me of Iceland, the country exploiting geothermal energy for a significant portion of its almost totally renewable energy consumption. This North Atlantic country is located at the junction of the Eurasian and North American tectonic plates, favorably for extracting heat from underground thermal ponds. Reykjavik’s streets and sidewalks are kept ice-free through recycling of its hot-water home heating. The country derives significant electricity from geothermal means as well.

Air-source. O’Malley describes, “The units you see that look like box fans outside homes and businesses are the more common air-source heat pumps. They wring energy out of outdoor air for heat and soak up excess heat indoors and move it out when they’re cooling. Geothermal heat pumps use underground temperatures, instead of outdoor air.”

Ground-source. “To install ground-source systems,” O’Malley says, “contractors bring in heavy equipment and drill to bury a loop of flexible piping several hundred feet deep in your yard. Water flowing through the loop takes advantage of the underground temperature, a pretty stable 55 F.” 

O’Malley continues, “Indoors, often in the basement, a unit contains refrigerant—a fluid that can easily absorb a lot of heat. In summer, the water in the loop dumps heat into the ground. In winter, it pulls heat from the earth with amazing efficiency and moves it indoors.”

O’Malley observes, “People who live in places with cold winters and hot summers reap the biggest savings. Still, leaders at three companies interviewed cited initial cost as a barrier.”

A Downside. Installation is a non-trivial endeavor: One builder told O’Malley that “systems can be put in yards as small as 15 by 15 feet…. But the drilling rigs can’t get in where homes are really close together.” 

Sticker Shock, But Tax Credits. O’Malley cites, “The sticker prices for ground-source are higher than traditional systems. But in a stamp of approval for their efficiency, last year’s Inflation Reduction Act highly incentivizes them, with a 30% tax credit. So a customer purchasing a $30,000 system would end up paying $21,000. If someone doesn’t owe enough taxes in one year to benefit from that, they can carry it over to the next year. Nor is there any dollar limit on the credit, unlike for air-source units, which are capped at a $2,000.”

She also notes that some states, South Carolina, for example, offer sizable credits for ground-source installation.

Operational Savings. O’Malley quotes one specialist noting that “Ground-source heat pumps average about 30 percent less electricity use than air-source heat pumps over the course of the heating season.” An Ontario, New York, homeowner told her that cooling the house (“typically 69 or 70 F”) cost perhaps $10/month and, even in the coldest winter month, the highest heating bill was around $70.

Ground-source from the Get-go. Ground-source specialists are working on partnerships with home builders, the idea to install geothermal instead of natural gas at 100 or 200 homes at a time. A specialist told O’Malley, “We really feel like we’re on the right side of a megatrend.” ds

© Dennis Simanaitis, SimanaitisSays.com, 2023