The AMS121HX 1 Ton Ductless mini wall split AC with 15500 BTU Heat Pump has two units: the compressor which sits outside of the home, and the air handler which is placed inside. A mini split air conditioner is very quiet and efficient, but it is more expensive than a window or portable air conditioner. Since they are ductless, the mini split AC/Heaters avoid the energy losses associated with the ductwork of central forced air systems.