Reducing the energy required for heating and cooling is essential to meeting the net zero goal. Air-source heat pumps are the most efficient heating and cooling system currently available. Air-source heat pumps take heat out of the air, even when temperatures fall below zero, and move it as hot refrigerant through a small pipe to one or more indoor units that deliver heat into the house. In the summer, air-source heat pumps remove heat from the homer, even when temperatures are above 100˚, and deliver cold refrigerant to the indoor units.