Matt Power
Converting to net-zero, all-electric living may take decades, unless we re-examine low-input energy sources such as ground source heat pumps.
This year, we learned firsthand that “all-electric” living won’t happen overnight in the United States. For example, our Scottsdale exhibition remodel took on the task of converting from gas to electric.
What we learned is that the electric grid, locally and regionally, may not be ready for such a huge new electrical load. Even with the addition of solar panels to generate electricity, a home using air-source heat pumps as its heating and cooling system, with a couple of electric cars in the garage, puts great strain on the nearest transformer.
But we all may have overlooked one ready-to-go solution: geothermal (ground source) heating and cooling loops. A geothermal system achieves much of its BTU output with the operation of small, energy-efficient pumps and a compressor. Modern air source heat pumps, with which almost every home builder is familiar, “extract” heat from ambient air to cool or heat an indoor living space. But compared to ground source heat pumps, they’re still energy-intensive.
Geothermal heat pumps require less of an electrical assist to achieve the same level of conditioning as air source heat pumps, gas, or oil-based furnaces. One key, according to international researchers, is that most other heating sources rely on high-temperature differences between inputs and outputs. Geothermal, on the other hand, takes a slow and steady approach, tapping into the natural, fairly consistent ground temperature of the Earth, or in some cases, a river or lake.
An eco-friendly house concept of ground- sourced geothermal for heating your home. (AdobeStock/181215388)
Heat From the Ground: The Big Picture
Over the last 20 years, the biggest changes in geothermal heating and cooling technology can be seen at larger scales.
“Surprisingly, even in cold northern climates, most of the HVAC system demand in commercial buildings is for cooling,” notes Paul Selking, vice president of commercial sales and marketing for WaterFurnace. He explains that because of all the appliances and other heat-producing equipment in these buildings, geothermal loops end up carrying away heat more often than introducing it. But inside that “waste” heat is energy treasure.
“It’s all about this heat recovery idea,” he explains, “With the advent of variable speed compression and variable speed pumping, this means I don’t need to pull more energy out of anywhere; I just need to share the heat where it’s needed in my space…even more so in bigger projects, commercial and multifamily.
“Ideally, you’re pulling off the cooling loop of your geothermal, and having that loop feed the domestic hot water heater, which has a sealed loop in it. The only wasted energy out of that whole thing is a little compressor heat, but that’s pretty minimal.”
Pond loop systems are also excellent souces for geothermal. Photo shows a twelve-ton pond loop heat exchanger system being sunk to the bottom of a pond for use in a heat pump installation. (Mark Johnson/Wikipedia.org)
Enhanced Geothermal Systems for the Home
On the residential side, cost of installation has been the tripping point for geothermal system. But those costs have shrunk somewhat, thanks to compact drills. Some new rigs are no bigger than a Bobcat attachment.
Along with the technology’s cost-effective operating cost, geothermal systems boast a long lifespan. This should be part of any return-on-investment (ROI) calculation.
“Even though the installation price of a geothermal system can be several times that of an air-source system of the same heating and cooling capacity, the additional costs may be returned in energy savings in five to 10 years, depending on the cost of energy and available incentives in your area,” notes Energy.gov. “System life is estimated at up to 24 years for the inside components and 50-plus years for the ground loop.”
By comparison, most estimates I found suggest that the best air source heat pumps last 15 years or less.
It’s shocking to note that only about 50,000 ground-source heat pumps have been installed to date. But I’m confident that as more people seek to achieve a net-zero lifestyle with solar, operating a ground-source heat pump will seem like a prudent and resilient choice. The pain of higher upfront installation costs will quickly dissipate as the house achieves a net-zero-plus energy footprint.
It’s not just that. With geothermal HVAC, a home can go fully off-grid with less battery storage. A couple of mini splits can quickly tap out a large solar array. With the same array and a geothermal system, the homeowners will have enough free, renewable electricity left over to power their smart, efficient, electric home.
Matt Power is Editor-in-Chief of Green Builder magazine and greenbuildermedia.com.
Reprinted with permission from Green Builder magazine’s April 21, 2022 blog at
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