In the 1920s residents living the dry, desert climates of the Southwestern US would regularly sleep on screened porches during the summer months. They learned that by soaking blankets in water, hanging the blankets over the screens and using fans, hot, dry air from outside could be pulled inside and cooled by as much as 30 degrees. This discovery of natural evaporative cooling inspired the development of machine evaporative cooling systems, or swamp coolers. In addition to being completely natural, the advantages of swamp coolers over conventional HVAC include:

Less Expensive to Install

The estimated cost of installation for a swamp cooler is generally about half that of conventional air conditioners.

Less Expensive to Operate

Since power consumption is limited only to the units fan and water pump – as opposed to compressors, pumps and air blowers on conventional A/C –  swamps coolers are 50% or less costly to operate.

Easier to Maintain

The only two mechanical parts in most basic evaporative coolers are the fan motor and the water pump, both of which can be repaired at low cost and often by a mechanically inclined homeowner.

Fresher Air

The constant and high volumetric flow rate of air through the building reduces the age-of-air in the building dramatically.Evaporative cooling increases humidity, which, in dry climates, may improve the breathability of the air.The pad itself acts as a rather effective air filter when properly maintained; it is capable of removing a variety of contaminants in air, including urban ozone caused by pollution, regardless of very dry weather. Refrigeration-based cooling systems lose this ability whenever there is not enough humidity in the air to keep the evaporator wet while providing a constant trickle of condensate that washes out dissolved impurities removed from the air.