During the summertime in many regions, you will hear the constant buzz of air conditioners as they cool homes and businesses. There are several types of air conditioners. One type is mounted in a window and typically only cools one room of a home. Another type has a unit outside, along with an indoor thermostat and return system. It can cool a whole house. Large businesses have even larger air conditioner units that are often mounted on the roof of a tall building.