Reducing the energy required for heating and cooling is essential to meeting the net zero goal. An air-source heat pump is the most energy efficient heating and cooling system currently available. It  takes heat out of the air, even when temperatures fall below zero, and moves it as hot refrigerant through a small pipe to one or more indoor units that deliver heat into the house. In the summer, an air-source heat pump removes heat from the home, even when temperatures are above 100˚F, and delivers cold air to the indoors.