Air source heat pumps are much more energy-efficient than traditional electric water heaters, as they extract heat from the surrounding air and elevate it to a higher temperature. Air-to-water heat pumps can significantly lower the energy consumption of your hot tub or spa thanks to their impressive COP (Coefficient of Performance). For instance, a unit with a COP of 12 can generate 12kW of heat energy for every 1kW of electricity it uses.