Window Units - As the name implies, if you have a unit that is stuck through a window – it is a window air conditioner. These units are useful as a solution for one room but they can be noisy, inconvenient and of course – block your view out of the window. These units are completely self-contained with a refrigeration system (see How an Air Conditioner Works) and fans to move the air.

Through the Wall Units - If you have ever stayed in a hotel or motel, many of them use a through the wall unit, commonly called a “PTAC”. Similar to a window unit, these systems are convenient for a small area, but sometimes can be noisy. These units are also completely self-contained, just like the window air conditioner.