How Does a Heat Pump Work? A Homeowner’s Plain-English Guide

A heat pump does not make heat. It moves heat that already exists, which is exactly why it can deliver three or four units of warmth for every unit of electricity it drinks.

Almost every explanation of a heat pump starts with a diagram of a refrigeration cycle and loses the reader by the second paragraph. Here is the version that actually matters when you are standing in your driveway with a contractor.

It moves heat, it does not create it

A gas furnace burns fuel to create heat. A resistance heater pushes electricity through a coil until the coil glows. Both are limited by physics: you can never get more energy out than you put in.

A heat pump plays a different game. It uses electricity to run a compressor and a pair of fans, and that machinery moves heat from one place to another. Even air at 20°F contains an enormous amount of thermal energy — absolute zero is another 480 degrees below that. The heat pump extracts a portion of it and releases it inside your house.

Because it is transporting heat rather than generating it, a heat pump routinely delivers 300–400% efficiency. Put in 1 kWh of electricity, get 3–4 kWh of heat. That ratio is called the coefficient of performance, or COP.

The four components you will hear named

1. Compressor — the heart of the system, in the outdoor unit. It squeezes refrigerant gas, which raises its temperature dramatically.
2. Condenser coil — where the hot refrigerant gives up its heat. In winter this is the indoor coil.
3. Expansion valve — drops the pressure of the refrigerant, which makes it very cold.
4. Evaporator coil — where the cold refrigerant absorbs heat from the surrounding air. In winter this is the outdoor coil.

Why it also cools

A single extra part — the reversing valve — flips the direction the refrigerant travels. Swap the roles of the two coils and the same machine now moves heat from inside your house to the outdoors. That is why a heat pump replaces both your furnace and your air conditioner with one box.

What this means for your electricity bill

If you currently heat with electric resistance — baseboards, a furnace with strip heat, an old air handler — a heat pump will typically cut your heating electricity by 55–70%. If you heat with cheap natural gas, the savings are far less certain and depend entirely on your local gas and electricity rates. Run the numbers before assuming a heat pump saves you money on operating cost; the case is often about comfort, air quality and getting cooling included rather than pure savings.

The one thing installers wish you knew

A heat pump is only as good as its installation. An oversized unit short cycles and never dehumidifies. Undersized ductwork chokes airflow and kills efficiency. A sloppy refrigerant charge can cost you 20% of rated performance on day one. The equipment brand matters far less than the person who installs it — which is why our contractor checklist is the most useful page on this site.

Last checked August 2026. Prices are US ranges and vary by region — always confirm against written quotes.