Heat pump pool heaters operate by extracting heat from the air and transferring it to your pool water. They use a refrigeration cycle, where a fan draws in outside air and passes it over an evaporator coil filled with refrigerant. The refrigerant absorbs the heat, which is then compressed to increase its temperature further. This hot gas moves through a heat exchanger that transfers the heat to the pool water, warming it up. The now-cooled refrigerant is recycled back to start the process again. This method is highly efficient, as it relies on ambient air rather than generating heat directly.