Ground-source heat pumps are one of the most energy efficient systems for heating and cooling a home. We don’t have one in our home, but our friend Martin installed one in his new home in suburban Maryland. So we made a trip to visit Martin’s home and interview him on his experience with the system.
Ground-source heat pumps are one of the most energy efficient systems for heating and cooling a home.
Heat pumps are a modern miracle—the most energy-efficient way to heat and cool your home. And they run on electricity, so they eliminate the need to burn natural gas or heating oil to generate heat from a furnace. Instead of burning a fossil fuel—generating harmful emissions in the process—heat pumps operating on only electricity transfer heat pulled from outside to warm the interior of a building. In warm weather, the process is reversed to air-condition a building by transferring heat to the outside.
Heat pumps are a modern miracle. Running on only electricity, they transfer heat pulled from outside to warm the interior of a building, achieving 300-400 percent energy efficiency.
The “magic”—achieved through the use of refrigerants and compressors—is that heat pumps provide more heat than the energy they use. That’s because they are not generating heat through combustion—they are transferring it between the outside and the inside of a building. When you burn natural gas in a furnace, the maximum level of efficiency is one unit of heat for each unit of energy used—and in practice, less than that. Heat pumps, on the other hand, can deliver three or four kilowatts of heat for each kilowatt of electricity they use to run the compressor and fans. That translates to 300 to 400 percent energy efficiency.
And energy efficiency means dollar savings on utility bills.
Energy efficiency means dollar savings on utility bills.
Replacing a furnace that burns natural gas or heating oil with a heat pump is also one of the most impactful ways to reduce carbon emissions, while also eliminating other harmful air pollutants that have the potential to enter your home. (That’s why you should have a carbon-monoxide detector if you have a furnace or water heater that burns fossil fuels.)
Replacing a furnace that burns natural gas or heating oil with a heat pump is one of the most impactful ways to reduce carbon emissions. Residential energy use is about one-fifth of total US consumption, and more than 40 percent of that is for heating.
Eliminating a furnace burning fossil fuels is one of the top two ways to de-carbonize your life—along with switching to an electric vehicle. Residential energy use is about one-fifth of total US consumption, and more than 40 percent of that is for heating. Much of residential heating is currently done with natural gas, with a smaller amount using heating oil, especially in the Northeast.
The solution to the climate crisis is to electrify our machines and make them more energy efficient, while powering the electricity from clean renewable energy from the sun and other non-carbon sources. Heat pumps—by electrifying space heating and maximizing energy efficiency—are one of the key elements of that electrified energy system of the future.
And while helping to solve the climate crisis, the efficiency of heat pumps can also save money on utility bills.
The solution to the climate crisis is to electrify our machines and make them more energy efficient, while powering the electricity from clean renewable energy from the sun and other non-carbon sources. Heat pumps are one of the key elements of that electrified energy system of the future.
Most heat pumps transfer heat between the air in a building and the air outside. They work well in most temperatures, but they start to lose efficiency in very cold or hot temperatures. My first home had a heat pump, installed in the early 1980s. I still remember watching a Superbowl game back then when the outside temperature was near zero and the heat pump became almost useless, even with its back-up electric heating element. I needed a portable electric heater and a blanket to stay warm.
Modern heat pumps with variable speed compressors and advanced refrigerants are much better than earlier generations, enabling them to operate at temperatures well below zero. There was a news article recently about people in Maine who have switched from furnaces burning expensive heating oil to heat pumps. In addition to saving money and reducing emissions, they have been pleased with the performance of their heat pumps in Maine’s cold northern climate.
Modern heat pumps with variable speed compressors and advanced refrigerants are much better than earlier generations, enabling them to operate at temperatures well below zero.
Nevertheless, air-source heat pumps do lose efficiency as they have to work harder in frigid temperatures, and they start to lose effectiveness in temperatures below minus-10 degrees.
Enter ground-source heat pumps.
Ground-source heat pumps are sometimes called geothermal heat pumps, though that term can be confused with geothermal power plants that generate utility-scale electricity by drilling wells deep into the Earth to capture steam to drive a turbine.
As the name implies, ground-source heat pumps transfer heat to and from the ground, rather than the outside air. The ground deep below the surface stays a relatively constant temperature of about 50 degrees. The benefit of this approach is that ground-source heat pumps have to do less work in cold temperatures to draw heat from the ground, rather than the air. That makes them more efficient and able to operate effectively in very cold—or hot—temperatures.
Ground-source heat pumps transfer heat to and from the ground, rather than the outside air. The ground deep below the surface stays a relatively constant temperature of about 50 degrees. The benefit of this approach is that ground-source heat pumps have to do less work in cold temperatures to draw heat from the ground, rather than the air.
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To learn more about ground-source heat pumps, RunningOnSouler interviewed our friend Martin at his new home in Maryland.
RunningOnSouler. Martin, thanks for taking the time to show us your ground-source heat pump system.
Martin. Happy to do it! I’m always happy to show off the system, which we love. And I’m also a big fan of RunningOnSouler. I follow all your posts on Instagram, and I read all the articles on the website.
RunningOnSouler. Good to hear! So let’s get started. How long have you had the system?
Martin. We had it installed when we built the house in June 2021. There were a few advantages of installing it during the construction of the house. There’s obviously some excavation to install the system—wells drilled 350-400 feet into the ground, and a trench from the wells into the basement. It’s best to do that during new construction or during a major addition. We also had all the necessary electrical circuits installed as part of the original plan for the house.
On the financial side, we got a credit from the builder for the regular HVAC system they otherwise would have installed, and we were able to roll the cost into our mortgage.
There were advantages of installing a ground-source heat pump during construction of a new house—including drilling the deep wells needed for the system.
RunningOnSouler. Other than the wells in the ground, there are no other parts of the system outside the house, right?
Martin. That’s right. It’s all under ground. So there’s no equipment outside the house as you see with a traditional air conditioner or air-source heat pump. That’s one of the things I really like about the system. There’s no noise from an outside unit. And with the rest of the system inside the house, there are no parts exposed to the weather, which, over time, should avoid problems caused by damaging cold, heat, moisture, and sun. So I expect the system to have a longer service life than an air-source heat pump.
There’s no equipment outside the house as you see with a traditional air conditioner or air-source heat pump, so there’s no noise and no exposure of external equipment to adverse weather.
RunningOnSouler. I imagine your neighbors really appreciate the absence of noise. Some of the air conditioners in our neighborhood make a real racket.
Martin. Well, in our case, I’m less concerned about the neighbors because the houses are pretty far apart. But I appreciate the lack of noise when we’re out on our deck.
RunningOnSouler. You mentioned some financial advantages from installing the system as part of the construction of the house. I’ve heard these ground-source heat pumps are pretty expensive.
Martin. Yes, you definitely pay more upfront. But as I said, we rolled the cost into the mortgage, which helps. And I expect the system will pay for itself over time with energy savings from its efficiency.
Ground-source heat pumps cost more upfront, but should pay for itself over time with energy savings from its efficiency.
RunningOnSouler. How much did your system cost?
Martin. We have a pretty big house, so we have a two-level system—one for the basement and first floor, and one for the second and third floors. That meant our system has three wells, rather than the usual two, as well as two units inside. The cost was about $45,000. But we got 26 percent of that back from the Federal tax credit, making a net cost of a little more than $30,000. I’m guessing a smaller system might cost several thousand dollars less than ours.
RunningOnSouler. Yes, I got a bid on the ground-source heat pump for our house a few years ago, and that was about $30,000, before the tax credit. I didn’t do it at the time because they would have had to dig up part of the driveway to drill the wells. Of course, we ended up having to replace the driveway a few years later anyway. So I’ve always regretted not installing one then—especially now that I’m hearing some pretty high numbers for regular heat pumps these days.
Martin. We certainly have no regrets. We’re very happy with the performance of the system. It keeps the house nice and warm in the winter and cool in the summer. One other comfort advantage is there is no need for a humidifier. Rather than the occasional blasts of hot air that you get with a furnace that burns fossil fuels, a heat pump system puts out a relatively steady stream of warm air. That results in a comfortable level of humidity with no need for a humidifier.
We’re very happy with the performance of the system. It keeps the house nice and warm in the winter and cool in the summer, and there is no need for a humidifier.
RunningOnSouler. How about the cleanliness of the air?
Martin. Yes, it’s hard to quantify, but my impression is that we have less soot coming out of the air ducts—simply because there’s no combustion in a furnace.
RunningOnSouler. The big selling point of these systems—the key to paying for the higher upfront cost—is energy efficiency and lower utility bills. What’s your experience with that so far?
Martin. Unfortunately, our system doesn’t have an app to directly monitor electricity use. So the best indication I have of its energy efficiency is the overall electricity use for the home. During almost two years of operation, we’ve averaged about 1600 kilowatt-hours of electricity use per month. Based on average residential electricity consumption numbers I’ve seen, that’s pretty good for an all-electric house of 3,900 square feet.
Over almost two years of operation, we’ve averaged about 1600 kilowatt-hours of electricity use per month, which is quite good for an all-electric house of 3,900 square feet.
RunningOnSouler. I’d say that’s really good. By comparison, our house is about 3,000 square feet. It’s well insulated and energy efficient. We use about 1,800 kilowatts of electricity per month, and we still use gas for heating and cooking. Of course, that number includes charging an electric car, which you don’t have yet, and that accounts for about 300 kilowatt-hours per month. So adjusting for EV charging, we use about the same amount of electricity, but you’re all electric and have a slightly larger house.
Martin. Right. So bottom line, we use an equivalent amount of electricity, but our house is bigger and all-electric, and you’re still using gas for heating, which is the biggest single source of energy use.
RunningOnSouler. So it sounds like the system is living up to expectations on energy efficiency. Any issues or problems with the system?
Martin. No maintenance or repairs needed so far in the first two years of operation. We have a Climate Master system installed by Metcalf & Sons. Climate Master is one of the leading makers of ground-source heat pumps. There are other good manufacturers with EnergyStar certification like WaterFurnace, GeoStar, and York. But the best advice we got was to go with a good local installer and the system they are familiar with.
Our Climate Master system installed by Metcalf & Sons has had no maintenance or repairs needed in the first two years of operation.
RunningOnSouler. I’ve also read about a new company called Dandelion Energy. They’re working to lower the upfront cost of geothermal heat pump systems, primarily by developing a less costly and invasive way of drilling the wells. They also deal with the upfront cost problem by offering loans that are paid with the customer’s energy savings over time. Supposedly, their systems can pay for themselves in seven years. The company was originally started as part of Google X but became an independent company a few years ago. Unfortunately, they’re only operating in the Northeast so far.
Martin. Well, that wasn’t an option for us.
RunningOnSouler. Nor for us, at least right now. So, Martin, with an all-electric house, the obvious question everyone wants to ask is, what happens if the power goes out?
Martin. That has actually happened to us out here a couple of times. We have a high-efficiency wood-burning stove as a supplement, which keeps the family room nice and toasty, even with the thermostat for the heat pump set at 68 degrees. It also serves as a backup source of heat if there is a loss of electricity. And there’s plenty of wood out here to keep us going indefinitely.
RunningOnSouler. What about the argument I hear all the time that your system isn’t really cutting emissions—it’s just transferring them to the electric utility.
Martin. When we built the house, we also installed a large solar system, with 48 panels providing a 19-kilowatt array. The panels face east and west on the garage roof—not ideal for solar production—but they should generate an average of about 2,000 kilowatt-hours per month, more than enough to power the house, and maybe even an electric vehicle some day.
RunningOnSouler. So won’t your solar system keep the electricity going to power the heat pump and your other power needs? You did include a battery backup, right?
Martin. Well, as I’m sure you know, the solar array goes down if the power goes out, because the inverter needs electricity to convert the DC power generated by the solar panels into AC power used in the house. At the time we built the house, the battery backups were pretty expensive. So right now, we have a generator for backup power.
RunningOnSouler. Well, you’ve certainly done a lot to reduce your carbon footprint. Thanks very much for your time today. It sounds like your ground-source heat pump was a great investment. And I definitely have solar panel envy now. Any last parting thoughts?
Martin. Well, I should have said earlier that I really am quite concerned about the climate problem. That’s one of the reasons we went all-electric with our new house, including the large solar system. And I like the idea of being energy independent—not to mention having essentially no utility bills.
I’ve read enough of the other articles on your website to know that the answer to the climate problem is to electrify all our machines, make them as energy efficient as possible, and power them with electricity from the sun and other non-carbon sources. With our ground-source heat pump, a heat-pump water heater, and a solar array, our home is pretty far along on the road to electrification, energy efficiency, and zero emissions.
RunningOnSouler. Yes, indeed—that’s music to my ears! But what about that gas-hog pick-up truck you drive to work? Have you reserved your electric F-150 Lightning yet?
Martin. I’m still waiting for a 1-ton version of an electric pickup truck, which I need to haul some heavy loads. But the garage is wired for a 240-volt charger when the time comes.
RunningOnSouler. OK, one step at a time. Take the wins where you can. Thanks again!