A ductless air conditioner typically consists of a wall-mounted indoor unit combined with an outside compressor. It’s most often used in a situation where a window AC unit or baseboard heating would be considered, such as a new addition to a house. But unlike window units, ductless units require only a very small hole to be drilled into the wall, making them less vulnerable to air leakage and security problems. Plus, they’re less visible and audible.
They’re also exceedingly energy-efficient. In the average house, you’re losing 25 percent or more of your energy to ductwork. Simply by removing the ducts, you end up with a more efficient system. Ductless models also have inverter-driven compressors, which speed up and slow down based on the needs of the system instead of shutting off entirely as traditional HVAC compressors do. You consume a lot of energy during compressor start-up.