Abstract: An air conditioner has an evaporator, a main compressor, a condenser, and an energy recovery device. The condenser receives a compressed refrigerant from the compressor and condenses the refrigerant to either a liquid phase or a saturated liquid-vapor phase (reduced refrigerant charge content). The condensed refrigerant is passed through the energy recovery device to expand the refrigerant. The refrigerant passing through the energy recovery device is regulated to maintain the refrigerant in a high cavitation region within the motor, while maintaining within a predetermined refrigerant pressure range in the motor. The condensed and compressed refrigerant is expanded, in the motor, to a saturated liquid-vapor phase having a higher vapor content before the refrigerant exits the motor to optimize energy recovery.