In the hot summer months, a window unit air conditioner can help cool rooms and make living more bearable. Keep in mind, though, that not all air conditioners are designed the same. Some are smaller and use less energy for smaller rooms, while larger ones are designed to cool large, open spaces. And units are designed to remove both heat and humidity from the air. Using a unit that is too large for the space will cool the room quickly, but will remove only some of the humidity. The result? A room that is damp and cold. The right size unit will create a perfect environment and save you energy in the long run.