An electric heat pump transfers heat from one location to another using electricity, refrigerant, and a compressor, rather than generating heat by burning fuel.
If you’re used to furnaces that blast hot air by burning gas or oil, a heat pump can sound like magic. The principle is the same one your refrigerator uses: the system doesn’t create heat; it moves it. In winter, it pulls heat from outside air or ground and brings it indoors. In summer, it reverses direction and pulls heat out of your home. This is a transfer machine, not a generation machine.
The Refrigeration Cycle at the Heart of Every Heat Pump
The process that makes a heat pump work is the vapor-compression cycle. It uses four main components — evaporator, compressor, condenser, and expansion valve — plus a sealed refrigerant loop never consumed. The whole thing runs on electricity. Here’s the sequence step by step:
- Evaporation: Cold liquid refrigerant passes through the outdoor coil (evaporator in heating mode). Outdoor air warmth causes the refrigerant to evaporate into a low-pressure gas.
- Compression: The compressor squeezes that gas, raising its pressure and temperature dramatically.
- Condensation: Hot, high-pressure gas flows through the indoor coil (condenser), releasing heat into your home. As it cools, refrigerant condenses back into a liquid.
- Expansion: Liquid passes through the expansion valve, dropping pressure and temperature sharply, making it cold enough to absorb heat again. The cycle repeats.
A reversing valve switches flow direction, flipping which coil acts as evaporator and which as condenser — the same machine heats in winter and cools in summer.
How Efficient Is a Heat Pump Compared to Other Systems?
According to the UK government, a heat pump can produce roughly 3 units of heat for every 1 unit of electricity used. Electric resistance heating (baseboard heaters or furnace backup) rarely exceeds 1-to-1. Performance drops as outdoor temperatures fall, though modern cold-climate models can extract useful heat at sub-freezing temperatures. Ground-source (geothermal) heat pumps stay more consistent because ground temperature is stable year-round, while air-source units see seasonal variation. Most residential installations use air-source models because they are dramatically cheaper to install.
| Heat Source Type | Typical Efficiency Range | Best Climate Fit |
|---|---|---|
| Air-source | 2–4 units heat per 1 unit electricity | Mild to moderate cold climates |
| Ground-source (geothermal) | 3–5 units heat per 1 unit electricity | Any climate; consistent output |
| Water-source | 3–5 units heat per 1 unit electricity | Where a body of water is available |
Common Misconceptions About Electric Heat Pumps
The biggest confusion comes from the word “heat” in the name. A heat pump moves existing heat, which is why it can deliver more energy than it consumes. Remember: your refrigerator moves heat out of the icebox so effectively that the back gets hot — same cycle, reversed in purpose.
Another assumption is that heat pumps stop working in freezing weather. While older models struggled below about 30°F, modern cold-climate heat pumps from brands like Mitsubishi and Fujitsu can extract heat from air as cold as -13°F, though efficiency drops. The system can still heat your home; it just uses more electricity per unit of heat as the temperature difference grows.
The sealed refrigerant circuit and electric compressor require professional installation and maintenance. A well-installed heat pump can replace both a furnace and an air conditioner with a single all-electric appliance, which is why they are central to electrification and decarbonization plans worldwide.
If you are researching whether a heat pump makes sense for your home, start with your climate’s winter design temperature and compare it to the rated operating range of models you consider. For a thorough roundup of top-performing electric heat pumps on the market, see our tested guide to the best electric heat pump models — it covers efficiency ratings, installation costs, and climate-specific recommendations.
FAQs
Can a heat pump heat a house in extreme cold?
Yes, modern cold-climate heat pumps can heat a home effectively at outdoor temperatures as low as -13°F, though efficiency drops. At very low temperatures, the system runs longer and uses more electricity. A backup heat source, usually electric resistance strips, can supplement during the coldest days.
Does a heat pump use a lot of electricity?
A heat pump uses electricity to run its compressor and fans, but typically uses less total electricity than electric resistance heating because it moves heat rather than creating it. Actual cost depends on local electricity rates, the unit’s efficiency rating, and climate. In moderate climates, heat pump operating costs often beat gas furnace costs.
How long do heat pumps last?
Air-source heat pumps typically last 10 to 15 years with proper maintenance, while ground-source systems can last 25 years or more for the ground loop and 15 to 20 years for indoor components. Regular maintenance — cleaning coils, changing filters, and annual professional checks — extends lifespan significantly.
References & Sources
- National Grid. “How do heat pumps work?” Explains the vapor-compression cycle and efficiency fundamentals.
- Carrier. “What Is a Heat Pump and How Does It Work?” Covers reversing valve operation and heating/cooling mode switching.
- UK Government. “Heat pumps explained: experts answer your questions.” Provides the 3:1 efficiency ratio and answers common user questions.