A standard air conditioner has a fixed speed compressor motor on 220 VAC. The compressor runs at full speed until the desired temperature is reached, then switches off. It starts again when the room temperature increases. Because the unit switches on and off frequently to restore temperatures to the desired level, it constantly runs at high power and as a result, is less energy-efficient than an inverter unit.
An inverter air-conditioner has a variable speed compressor motor that adjusts to control its cooling and heating capacity as required. This makes it more economical and energy-efficient than its non-inverter counterparts. While these units cost a little more to buy, their low operating costs save you money and electricity usage in the long run.