Heat pump

A heat pump is an electrically driven device that moves heat from a colder place to a warmer one, and many models can also run in reverse to cool a building. Because it moves heat instead of making it by burning fuel, a heat pump can deliver up to three times more heat energy to a home than the electrical energy it uses, according to ENERGY STAR.

History of heat pumps

The heat pump uses the same refrigeration cycle as a refrigerator or an air conditioner, so its history is tied to the history of mechanical cooling. A 1978 review by J. Fearon in the British trade journal Refrigeration and Air Conditioning traced heat pump development in Europe and the United Kingdom from 1834 onward.

The review covered systems that took heat from water, from air and from the ground. It also covered their use for heating, cooling and heat recovery in commercial, public and residential buildings. It concluded that installations worked best when their designs included some diversification or thermal storage, and it reported a renewed interest in heat pumps at that time.

How a heat pump works

A heat pump extracts heat from a low-temperature place, called the source, and delivers it to a higher-temperature place, called the sink. Heat naturally flows from warm to cold, as thermodynamics describes, so the machine uses electrical energy to push it the other way.

Inside the machine, a refrigerant circulates between an outdoor coil and an indoor coil. In heating mode the refrigerant picks up heat outdoors, a compressor raises its pressure and temperature, and the indoor coil releases the heat into the home. A reversing valve switches the flow so the same equipment removes heat from the house in summer, which is the principle behind air conditioners and refrigerators.

Cold air still holds usable heat. Natural Resources Canada notes that air at minus 18 degrees Celsius contains about 85 percent of the heat found in air at 21 degrees Celsius, which is why an air-source unit can keep heating in cold weather.

Performance is described with ratios. The coefficient of performance (COP) divides the heat delivered by the electrical power used, so a unit that uses 1 kilowatt of electricity to move 3 kilowatts of heat has a COP of 3. Seasonal measures such as the heating seasonal performance factor (HSPF) average the results across a whole heating season instead of one operating condition.

Types of heat pumps

Heat pumps are grouped mainly by the source they draw from. Air-source units take heat from outdoor air and are the most common type on the Canadian market. They can be ducted, connecting to the forced-air ductwork found in most American homes, or ductless.

ENERGY STAR explains that mini split heat pumps mount on an interior wall or ceiling and connect to an outdoor unit without any ducts, which suits homes that lack ductwork.

Ground-source heat pumps use the earth or groundwater as the heat source in winter and as a place to dump heat in summer. They need a ground heat exchanger, which can be an open loop that uses groundwater or a closed loop of buried piping. The entry on the geothermal heat pump covers this type in more detail.

A dual-fuel system pairs an electric heat pump with a natural gas or oil furnace. ENERGY STAR notes that this lets owners heat with whichever system costs less or performs better at a given time.

Applications of heat pumps

Most residential use is space heating and cooling. Some systems also heat domestic hot water, and ENERGY STAR describes water-to-water geothermal units that supply space conditioning, water heating or both. Natural Resources Canada says heat pumps suit both new homes and retrofits, and that replacing a cooling-only air conditioner with a heat pump often adds only a small incremental cost.

Cold climates need extra care. ENERGY STAR says many newer certified air-source units heat well in very cold weather because of advanced compressors and refrigerants. It still advises owners where winter temperatures regularly fall below freezing to ask a contractor which unit suits the home.

Size matters as well. A unit that is too large or too small will struggle to keep a house comfortable, so installers use a calculation called Manual J to estimate how much heating and cooling a home needs.

Advantages and disadvantages of heat pumps

The main advantage is efficiency. The figure of up to three times more heat energy than the electricity consumed is a ceiling, not a guarantee, and real performance varies with outdoor temperature and system design. ENERGY STAR reports that certified geothermal heat pumps use 61 percent less energy than a standard model.

Heat pumps also burn nothing on site. ENERGY STAR points out that this means no direct emissions of nitrogen oxides, carbon dioxide or carbon monoxide inside the home, and no fuel to store or run out of. Replacing a furnace that burns fossil fuel shifts the energy demand to electricity, so the overall effect on emissions depends on how that electricity is generated.

The drawbacks are real. Ground-source systems can cost more to buy and install, although ENERGY STAR states that lower energy bills repay the difference over time. Frost is another limit: near or below freezing, moisture condenses and freezes on the outdoor coil, which reduces its ability to transfer heat.

To clear the frost, the unit switches into a defrost mode. Natural Resources Canada describes the usual method, in which the reversing valve briefly runs the machine in cooling mode to send hot gas to the outdoor coil, so a supplementary heat source may be needed during that time.

Lifespan is a further consideration. Natural Resources Canada gives a service life of 15 to 20 years for air-source heat pumps and calls the compressor the critical component.

Heat pump vs. furnace

A furnace creates heat by burning fuel or running electric resistance elements, so it cannot deliver more heat than the energy it consumes. A heat pump moves existing heat, which is why its output can exceed its electrical input. A furnace does not need to defrost an outdoor coil, and a dual-fuel setup lets a home use both.

ENERGY STAR adds that switching from electric resistance, propane or oil to a heat pump can lower energy bills.

Editorially reviewed by Specialty Digest Editorial TeamLast reviewed November 4, 2026Researched and drafted with AI assistanceReport an issue