A heat pump is a machine that moves heat instead of creating heat directly. In cold weather, it can pull heat from outside air, ground, or water and move it indoors. In warm weather, it can work in the opposite direction and move heat out of the building, acting like an air conditioner.
The name can sound strange because people often think heating means burning fuel or making something hot. A heat pump works more like a refrigerator in reverse. A refrigerator moves heat from inside the cabinet to the room. A heat pump can move heat from outside to inside, even when the outside air feels cold.
Heat pumps use a refrigerant, a compressor, coils, and valves. The refrigerant absorbs and releases heat as it changes pressure and temperature. Because the system mainly moves heat, it can be more efficient than electric resistance heating, where electricity is converted directly into heat.
There are different types of heat pumps. Air-source heat pumps exchange heat with outdoor air. Ground-source, or geothermal, systems exchange heat with the ground. Some units heat and cool a single room, while others connect to ducts or water systems for a whole building.
The advantage of a heat pump is efficiency, especially in moderate climates and in well-designed systems. The exact performance depends on the model, weather, insulation, and installation quality. A good heat pump can reduce energy use while still keeping a space comfortable.