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What are heat pumps and why would you want one?

SANTA FE, N.M. — I was visiting our friends Joe and Alice Hardy in their home in coastal southern Maine a year or so ago. They have solar panels and wood stoves but, as Joe explained, they also have a heat pump.

“What are heat pumps?” I asked. Joe tried to explain how heat pumps work. “They work a lot like refrigerators, you know,” he said, assuming I knew all about how refrigerators work. I honestly didn’t understand what he was saying at the time or its implications.

So, what are they and how do they work? As I have since learned, heat pumps are an efficient home heating and cooling system that can save you money. They work because, believe it or not, heat can be extracted from cold air.

Joe was right. Our refrigerators are a lot like heat pumps. But a heat pump has a condenser unit that is outside your house. It yields both hot and cold air, and it also has an indoor unit that passes the hot or cold air into your home. Heat pumps use electricity and refrigerant to move heat from one location to another. A heat pump extracts heat from the air, transferring it to the coolant. When the coolant is compressed, heat is produced. Then the coolant is transferred to the indoor unit, where it releases heat.

What heat pumps do is provide heat, air-conditioning and humidity control. In the cold time of year, they move heat from outdoors to your home. In the hot time of year, they move heat from your house to the outside. And, as Consumer Reports states in its buying guide, they are often more cost-efficient than conventional furnaces, which generate heat by burning fossil fuels. The most common are air-source systems. They have both an indoor and an outdoor unit. The refrigerant circulates between the two units absorbing and releasing heat. But Consumer Report says that, if your winter temperatures are below 10 to 25 degrees, you will need an auxiliary heating system.

When this concept is applied to residential heating and cooling applications, it works because, in a heat pump, less energy is used to produce the hot or cold air than the heat or cold generated. And heat pumps work well for both applications. They also improve indoor air quality since fresh air is introduced into your home.

It seems counterintuitive, but even extreme cold has heat energy, and the heat pump extracts it and transfers into your home. However, they are not as efficient in cold temperatures, since more heating than cooling is required. So, in colder climates, heat pumps often require a back-up heating source. And make sure your home is well-insulated before you consider a heat pump. If you have a super insulated home, they could work very well.

There are three basic types: air source described above, water source should you have a nearby body of water, and ground source or geo-thermal. They all gather heat from different sources. The cheapest and easiest is air-source, but they need to be customized for maximum efficiency. Both ductless and ducted systems are available and they can be multi-zoned. All systems sold have an EnergyGuide label that explains their heating and cooling efficiency.

You can get a lot of information about heat pumps at, or you can just ask your plumber, like I did.

My plumber referred me to Bob Deeds of Santa Fe Home Services. Bob moved here from Phoenix. He told me, “Almost everyone in Phoenix is using heat pumps for both heating and cooling. They are up to three times more efficient than conventional systems.”

He installs heat pump systems regularly. But he cautioned, “here, you may need auxiliary heat and heat pumps are electric, so heating bills may be higher. Most people who put them in here do so for cooling because conventional cooling systems require so much maintenance.”

Bob believes that, as we transition more from fossil fuels, heat pumps will play a much bigger role and that, eventually, heat pump systems will be automatically placed in new homes.

Joe Hardy runs his heat pump with solar. According to Joe, Efficiency Maine, a statewide program, hopes to help install 100,000 residential heat pumps in the next five years.

If it is time to replace your old furnace, you might consider a heat pump. Heat pumps can play a large role in reducing global emissions as we move from a carbon-intense economy. The bottom line is that, if they work in Maine, they can work even better here in a much warmer climate.

Judith Polich/For the Journal


Judith Polich, a longtime New Mexico resident, is a retired attorney with a background in environmental studies and is a student of climate change. She can be reached at”>href=”http://judith.pol”>