Many minisplit air conditioners and heat pumps use inverters for efficiency. Conventional split system air conditioner and heat pumps can now be purchased with inverters for ultra efficient heating and cooling.
Inverter air conditioners came to the USA in the form of ductless mini-split air conditioners and were later expanded to ductless mini-split heat pumps. Inverter air conditioners and inverter heat pumps are considered the most efficient air conditioners and heat pumps available on the market for conventional systems and for air source air conditioners and air source heat pumps the inverter air conditioners and inverter heat pumps come close to matching the efficiency of geothermal heat pump systems. In fact some inverter air conditioners and inverter heat pumps beat some geothermal heat pump systems when matched up for efficiency. If it is impractical to drill a well or do trenching for a geothermal system and you want very high efficiency the next best thing is an inverter air conditioner or an inverter heat pump. Of course with any air source heat pump geographical considerations must take precedence as air source heat pumps are not practical in the northern climates for technical reasons unless they are specially engineered heat pumps for operation in the Northern climate region.