Most Phoenix residents who have the option of choosing between the two systems, tend to use the evaporative air conditioner during the hot dry months of May, June, September and October and switch to refrigerated air during July and August, the two hot humid months. Another serious limitation is the large amount of water used by evaporative coolers. Recent estimates of the average water consumption in the Phoenix area ranges from 100-240 gallons per day. In regions where water supplies are limited, evaporative cooling may be an unreasonable luxury. Evaporative coolers have many advantages over refrigerated air conditioning systems.
Energy usage is roughly one third that of refrigerated systems.
Evaporative coolers are cheaper to install and maintain. Most of the time the home owner can perform routine maintenance and if maintained properly the unit brings fresh moist air into the home, providing a healthy environment for plants and animals. The refrigeration cooling at the Desert House is a heat pump air conditioning system. Unlike the evaporative system described above, the heat pump provides cool dry air during the cooling season and warm dry air during the heating season. Heat naturally flows from warm areas to cool areas until a temperature equilibrium is reached.