Heat pumps move warmth from outside air or ground into your home, rather than generating heat by burning fuel or using resistance coils

A heat pump is a machine that captures heat that already exists — in the air outside, in the ground, or in water — and moves it indoors. It does not create heat the way a furnace does. Instead, it uses electricity to run a cycle that pulls warmth from a colder place and pushes it into a warmer one, much like a refrigerator works in reverse. In winter, it extracts heat from outside air (even when it feels cold) and moves it inside. In summer, it reverses and pulls heat out of your home to cool it down.

The reason this matters is efficiency. Moving heat uses far less electricity than generating it. A heat pump can deliver three to four units of heat for every unit of electricity it consumes, whereas an electric resistance heater delivers only one unit of heat per unit of electricity. That difference shows up directly on your heating bill.

Key Takeaways

  • Heat pumps move existing heat from outside into your home using a refrigerant cycle, rather than creating heat through combustion or resistance.
  • The cycle relies on a compressor, condenser, expansion valve, and evaporator working together to change the refrigerant between liquid and gas states.
  • Air-source heat pumps pull heat from outdoor air and work in most climates; ground-source heat pumps pull from soil and cost more upfront but run more efficiently.
  • Heat pumps can both heat and cool your home by reversing the direction of the refrigerant flow.
  • Efficiency drops in very cold weather, so many heat pumps include a backup electric heater for temperatures below freezing.

The refrigerant cycle: how the four main parts work together

A heat pump contains a sealed loop of liquid called refrigerant that circulates through four main components. The refrigerant changes state — from liquid to gas and back again — as it moves through the loop, and those state changes are what allow the pump to move heat.

The evaporator sits outside (in an air-source pump) or underground (in a ground-source pump). Cold refrigerant flows through it and absorbs heat from the surrounding air or soil. The refrigerant boils and turns into a gas, carrying that heat with it. The compressor then sucks in that warm gas and squeezes it under high pressure, which makes it even hotter — hotter than the air inside your home. That hot, pressurized gas flows to the condenser, which is inside your house. As indoor air blows across the condenser, the hot refrigerant gives up its heat to that air, and the refrigerant cools down and turns back into a liquid. Finally, the expansion valve reduces the pressure on that liquid refrigerant, which makes it very cold again, and it flows back to the evaporator to repeat the cycle.

The compressor is the only part that requires electricity. Everything else happens because of the pressure and temperature changes the compressor creates. In summer, the cycle reverses: the evaporator moves inside and the condenser moves outside, so heat is pulled from your home and dumped outside instead.

Air-source heat pumps: the most common type

An air-source heat pump has its evaporator coil in an outdoor unit and its condenser coil indoors (or vice versa in cooling mode). It pulls heat from the outside air, even when the air is cold. This works because air always contains some heat energy — even at 20°F, there is still heat to extract, though the pump has to work harder to get it.

Air-source pumps are cheaper to install than ground-source pumps because they do not require digging. They work in most climates, though their efficiency drops as outdoor temperature falls. Below about 25°F to 35°F (depending on the model), the amount of heat available in the air becomes small enough that the pump's compressor has to run almost constantly, and the system becomes less efficient than a backup electric heater. Many air-source systems include a supplemental electric heater that kicks in automatically during very cold weather.

An air-source pump can be a split system, where the outdoor unit connects to an indoor air handler, or a ductless mini-split, where one or more small indoor units hang on walls or sit on floors and connect directly to the outdoor unit. Split systems work with existing ductwork; mini-splits do not require ducts at all.

Ground-source heat pumps: higher upfront cost, steadier performance

A ground-source heat pump (also called a geothermal pump) pulls heat from the soil or groundwater instead of air. Soil temperature stays relatively constant year-round — usually between 45°F and 60°F depending on your location — so a ground-source pump can extract heat even in the coldest weather without losing much efficiency.

The trade-off is installation cost. The system requires either a vertical borehole drilled 100 to 400 feet deep, or horizontal loops buried 4 to 6 feet down across a large area of your property. Drilling and trenching are expensive, so ground-source systems typically cost two to three times more upfront than air-source systems. However, they run more efficiently over their lifetime, so the higher initial cost can be recovered through lower heating and cooling bills over 15 to 25 years.

Ground-source systems are most practical if you have space for the loops, stable soil conditions, and plan to stay in your home long enough to recoup the installation cost. They also require less maintenance than air-source pumps because the outdoor heat exchanger is not exposed to weather.

Why efficiency matters: comparing heat pumps to other heating methods

A heat pump's coefficient of performance (COP) is the ratio of heat delivered to electricity used. An air-source heat pump typically has a COP of 2.5 to 3.5 in moderate weather, meaning it delivers 2.5 to 3.5 units of heat per unit of electricity. A ground-source pump can reach 3.5 to 5.0 because the soil temperature is more stable.

By comparison, an electric resistance heater has a COP of 1.0 — it converts electricity directly to heat with no multiplier. A gas furnace is about 90% efficient, meaning 90% of the fuel's energy becomes heat, but it still burns fuel rather than moving existing heat. Over a heating season, a heat pump can cut heating costs by 30% to 50% compared to electric resistance heating, and by 20% to 40% compared to gas heating in many climates.

The savings depend on your local electricity rates, gas rates, and how cold your winters are. In regions with very cheap natural gas and mild winters, the payback period may be longer. In regions with expensive electricity and very cold winters, an air-source pump's efficiency drops enough that a gas furnace or hybrid system (heat pump plus gas backup) may be more cost-effective.

Backup heating and performance in cold weather

Most air-source heat pumps include a backup electric resistance heater that turns on automatically when outdoor temperature drops below a set point — usually between 25°F and 35°F. This heater is less efficient than the heat pump itself, but it ensures your home stays warm even when the pump cannot extract enough heat from the cold air.

Some newer heat pumps can operate efficiently down to 0°F or below, which reduces the need for backup heating. These cold-climate heat pumps use larger compressors and improved refrigerants to maintain performance in extreme cold. If you live in a region with frequent sub-zero temperatures, a cold-climate model can lower your heating costs compared to a standard air-source pump.

A hybrid system pairs a heat pump with a gas furnace. The heat pump runs when it is efficient enough, and the furnace takes over during very cold weather. This approach can reduce energy costs in climates where heating is needed for many months and winter temperatures often drop well below freezing.

Maintenance and how long heat pumps last

Heat pumps require less maintenance than furnaces because they have no combustion, no fuel line, and no chimney. The main tasks are keeping the outdoor coil clean (especially for air-source pumps), replacing the air filter regularly, and having a technician check the refrigerant charge and electrical connections every one to two years.

A well-maintained heat pump typically lasts 15 to 20 years. The compressor is the most expensive part to replace, and compressor failure usually means replacing the entire outdoor unit rather than repairing it. Ground-source systems often last longer — 20 to 25 years — because the underground loops are protected from weather and the compressor runs at more stable temperatures.

Regular maintenance extends the lifespan and keeps efficiency high. Neglecting filter changes or allowing ice to build up on the outdoor coil can force the compressor to work harder and shorten its life.

Frequently Asked Questions

Can a heat pump work when it is freezing outside?

Yes, but with reduced efficiency. Heat exists in air even at 0°F, so the pump can extract it — the compressor just has to work harder. Most air-source pumps include a backup electric heater that turns on below 25°F to 35°F. Cold-climate heat pumps can operate efficiently down to 0°F or lower, though they cost more upfront.

Do heat pumps make noise?

The outdoor unit makes noise similar to an air conditioner — typically 50 to 60 decibels, about as loud as normal conversation. Ductless mini-splits are quieter indoors because the compressor is outside. Ground-source systems are quieter overall because the outdoor unit is smaller and the compressor runs at lower speeds.

Can I use a heat pump with my existing ductwork?

Yes, if you have a split-system air-source heat pump. The outdoor unit connects to an indoor air handler that fits into your existing duct system. If your home has no ducts, a ductless mini-split system can be installed without adding them.

How much does a heat pump cost to install?

Air-source heat pumps typically cost between $4,000 and $8,000 installed, depending on the size and whether you need new ductwork. Ground-source systems cost $15,000 to $30,000 or more because of drilling or trenching. Many states and utilities offer rebates that can reduce the upfront cost.

Will a heat pump lower my electric bill if I switch from gas heating?

Not always. A heat pump uses electricity instead of gas, so your electric bill rises and your gas bill drops. Whether your total bill goes down depends on the price difference between electricity and gas in your area, how cold your winters are, and how efficient your current furnace is. In regions with cheap gas and expensive electricity, the total bill may stay similar or increase.