Heat pumps use energy stored in the air and convert this to heat for space heating and hot water production. Low temperature energy from the air is collected through a CFC-free refrigerant cycle, which converts this energy to higher temperatures for use inside the home.

Heat withdrawn from the air is transferred to the refrigerant. The refrigerant absorbs the heat and changes from a liquid to a gas. The gaseous refrigerant is then passed through a compressor. As the gaseous refrigerant is compressed, its temperature increases further. The heat from the gaseous refrigerant is now directly transferred to the heating circuit.