In recent times, central air conditioners have improved greatly, not only have the SEER ratings gone up but many other additions have been made so enhance efficiency and comfort. They are variable-speed air handlers which regulates the blower output speed across a range of speeds, the two-stage compressor automatically senses the cooling requirement of your home and lowers the output which in turn saves electricity consumption and the thermal expansion valve which reacts to the room's changing cooling load and meters the flow of refrigerant through the evaporator and the condenser coils thus preventing flooding of the compressor with the liquid refrigerant.