Evaporative Cooler Tips

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  • Use a two-speed blower motor. A cooler operates in low speed (which is its more efficient mode) 60%-80% of the time.
  • Use a low-voltage thermostat. High-voltage thermostats permit greater temperature swings, although they are better than no thermostat at all. Manual control wastes energy and can allow the house to get uncomfortably cold at night. (Many people trade in their evaporative coolers for air conditioners when all they really need is a $50 thermostat.)
  • Provide a minimum of 3 feet of clearance on any side of the cooler that requires access for maintenance.
  • Provide an easily accessible water shutoff for rooftop installations. If your cooler suddenly starts to leak, you don't want to have to run around looking for a ladder.
  • Provide an electrical disconnect near the cooler to facilitate safe maintenance. This is particularly important for rooftop installations. When the disconnect isn't handy, it's a temptation to work on the live cooler. Better units now come with a disconnect.
  • Be sure the cooler inlet is 10 feet away from, or 3 feet below, plumbing vents; gas flues; clothes dryer vents; or bathroom, kitchen, or laundry exhaust fan vents.

Water Use

Evaporative coolers use a lot of water. This should be a consideration if you live in an area where water conservation is important.

To prevent the water reservoir from becoming saturated with minerals, evaporative coolers use more water to flush them out. A bleed-off system drains a small amount of water from the cooler whenever it is running. A "sump dump" system evacuates the water from the reservoir every half-hour or so. Sump dump systems are more effective than bleed-off systems because they discharge not only brackish water but also some of the enormous amount of filtered dirt that collects in the reservoir.

Map of the United States illustrating summer wet-bulb temperatures.

Summer wet-bulb temperatures in the United States can show where evaporative coolers are most effective. The lines mark areas where the wet-bulb temperature is below the indicated number 99% of the time. An evaporative cooler is most appropriate for areas with wet-bulb temperatures below 70°F, where they can meet all or most of a house's cooling needs. They are also effective for much of the summer in areas with wet bulbs between 70°F and 75°F.

Excerpted with permission from No-Regrets Remodeling by Home Energy (1997)