An evaporative cooler (also called a “swamp cooler”) is a completely different type of air conditioner that works well in hot, dry climates.
These units cool outdoor air by evaporation and blow it inside the building, causing a cooling effect much like the process when evaporating perspiration cools your body on a hot (but not overly humid) day. When operating an evaporative cooler, windows are opened part way to allow warm indoor air to escape as it is replaced by cooled air.
Evaporative coolers cost about one-half as much to install as central air condi- tioners and use about one-quarter as much energy. However, they require more frequent maintenance than refrigerated air conditioners and they’re suitable only for areas with low humidity.
Evaporative coolers cost about half as much as central air conditioners and use about 25% less energy.