Air-to-water heat pumpAir-to-water heat pump provides energy-efficient and environmentally friendly heating for your home. An air-to-water heat pump is suitable as the main heating system for a house. It collects heat from the outside air and transfers it to underfloor heating or radiators, and also heats domestic water. The outside air contains heat all the way down to absolute zero (-273.5'C). The operating range of the devices does not extend quite that far, but high-quality devices operate with good efficiency even in temperatures of -25 - -30.