Recent advancements in mini-split technology have led to improvements in efficiency, with inverter compressors replacing traditional rotary compressors in many systems. The main difference between the two is that rotary compressors can only be either on or off, while inverter compressors can adjust their speed according to the heating or cooling needs of the space, resulting in improved efficiency. Energy Star has reported that Energy Star certified units with variable-speed compressors and fans can result in lower heating and cooling costs.