An air conditioner (often referred to as AC or air con) is an appliance, system or machine designed to change the air temperature and humidity within an area (used for cooling as well as heating depending on the air properties at a given time), typically using a refrigeration cycle but sometimes using evaporation commonly for comfort cooling in buildings and motor vehicles.

This is the most prevalent and economical air conditioner system. It sits in a window with its rear releasing hot air into the environment and cool air into the room. The air in the room is cooled as a fan blows it on the cool evaporator unit. The condenser releases the hot air outside. The controls are on the side that faces inwards.

Split AC as the name indicates is designed in such a way that the two key functions of the AC are split into two compartments. One is the hot side, i.e. the compressor condenser unit, and the other is the cool side, i.e. the expansion valve and the evaporator unit.

The splitting of the two units allows one to install the cooling unit inside and the hot noisy unit outside. Since two units are separate individually, they can be larger and thus the AC can be easily designed to be more powerful than windows AC. Window ACs have size limitation and therefore they cannot exceed certain capacity.

Since the compressor condenser unit can be installed outside the building, the room where the AC is installed can still be quiet. Split ACs are an excellent option for office use and for large commercial buildings. Due to their compact size and affordable prices, split ACs have become popular for even household usage.

Split ACs do not work well in case of multi-storied buildings where connecting the room units with the exterior condenser becomes a difficult task.