Non-inverter air conditioning units are the most common type of unit available. These air conditioning units operate on the "all or none" principle when it comes to controlling the compressor. An air conditioner's compressor is the part of the unit that compresses the refrigerant into liquid form and then allows it to expand by shutting off. The refrigerant begins to cool as it expands, creating the desired cooling effect. In a non-inverter unit, this process happens when the compressor starts and then subsequently stops. Non-inverter units deliver a fixed amount of power to the compressor, which then runs at a fixed speed.
Inverter air conditioners run on variable speeds, rather than at a fixed speed. The process is slightly more complicated than that though. The reason for the variable speed control is to allow the compressor motor to control the compressor on an "as needed" basis, rather than having the compressor run at full power all of the time that it is on. Instead, the system converts alternating current to direct current, which is then stepped down to the desired level of current to control the compressor motor.
The primary purpose of an inverter system is to run the air conditioner in a way that reduces the inefficiency of the constant starting and stopping associated with non-inverter units. Non-inverter units must use considerable power and energy to start the compressor motor and to then keep it running afterwards. The inverter unit does not start and stop periodically. Instead, it keeps the compressor motor running at speeds needed to provide compression as needed, with reduced power and speed.
The advantages of an inverter system stem primarily from the increased energy efficiency of the unit. In many cases, this increased energy efficiency results in a 30 to 50 percent savings over less efficient conventional non-inverter units. However, Whirlpool does note that a high efficiency non-inverter unit can result in significant energy savings also. Inverter units tend to run more quietly and often require less time to reach the desired cooling temperature. The lack of peak voltage fluctuations tend to make inverter units less harsh on the compressor and compressor motor as well, increasing the life of the unit.