A heat pump extracts heat from the outside air, the ground or groundwater and raises it to a usable temperature for heating and hot water. Because it mainly moves heat rather than generating it, 1 kWh of electricity delivers several kWh of heat — expressed as the COP.
Efficiency depends on the envelope
Heat pumps work most efficiently at a low flow temperature. Good insulation, airtightness and delivery via underfloor heating or low-temperature radiators are therefore crucial — especially when renovating existing homes.
Types
Air-to-water is most common and relatively cheap; ground-source is more efficient but costlier to install. A hybrid setup with a gas boiler as backup is a common intermediate step.