In a hybrid energy centre, heat pumps are sized to provide the maximum share of energy (kWh) but are not sized to the peak building load (kW) as this is extremely expensive and results in over-sized, under utilised appliances. Hence, cost effective peak capacity should be provided by boilers.
Heat pumps use a vapour refrigeration cycle to generate hot water
by harvesting energy from a lower temperature source. This source is generally air or water, and could be from the ambient air, exhaust air, river water, bore hole, mine water and many others. The input energy is electricity to power compressors and fans if the source is air. Efficiency is the ratio of heat output divided by electricity input, known as COP (Coefficient of Performance).