Definition
A heat pump is an electrically driven machine that moves heat from a cooler source (air, ground or water) to a warmer place, such as a building's heating system, using a refrigerant cycle. Because it transfers existing heat rather than generating it by combustion, it typically delivers 3–5 kWh of heat per kWh of electricity. Heat pumps are classified by source and sink, for example air-to-water or brine-to-water.