Evaporative coolers use a substantial amount of water to run. Systems with bleed valves and sump dump systems use the most water. This should be taken into consideration in areas where water is expensive or in short supply.
A study conducted by the University of Arizona’s Office of Arid Lands Studies at the request of the city of Phoenix tried to quantify exactly how much water is used by evaporative coolers. The study found that average daily water use was 66 gallons per day, or 14,000 gallons per year (212 days of cooling). Coolers without a bleed valve used an average of 3.5 gallons per hour, while the coolers with a bleed valve used 10.5 gallons per hour. The percentage of household water used by the coolers was 25.8% for households without air conditioning, and 15.8% for all houses. On average, coolers ran 2,100 hours during the summer (Karpiscak et. al. 1998). Similar results were found in a study conducted in El Paso, Texas (Tarquin 1999).
||Average water use (gal/hr)
||Average run time (hr/yr)
||Yearly water use (gal/yr)*
*Extrapolated from Karpiscak et. al. 1998 study.
Source: Karpiscak et. al. 1998
In general, the amount of water used by your evaporative cooler will depend upon its size, air movement, and the relative humidity of the air. All things being equal, a 4500 CFM cooler uses less water than a 6000 CFM cooler. However, the most important difference is water usage rates for evaporative coolers is the use of bleed water.
Thermostats and timers can be utilized to decrease the amount of water (and energy) used by evaporative coolers. A thermostat can be set to a certain temperature so that the evaporative cooler is only used when necessary. In addition, timers can be used so that the evaporative cooler can turn on just before residents get home.
“Evaporative cooler water use” by Martin Karpiscak of Arizona Cooperative Extension. Accessed April 11, 2003.
Karpiscak, M.M., et. al. 1998. Evaporative cooler water use in Phoenix. Journal AWWA, 90(4): 121-130.
“Save Water Money and Your Health with an Evaporative Cooler” Accessed May 13, 2003. Tarquin, A. J. 1999. Water Use for Evaporative Cooling. El Paso, TX: U.S. Bureau of Reclamation.