Evaporative coolers, or “swamp coolers,” are environmentally friendly, cost effective alternatives to conventional air conditioning systems. Evaporation is the most energy efficient means of cooling. Evaporative coolers operate on the same principle as perspiration, cooling the indoor environment using water and air circulation. A fan draws warm air into the cooler where the air passes over moist pads for “an evaporative cooling effect.”

Evaporative coolers may be:

  • Ducted (available in standard and inverter models) or
  • Inverter model types that have variable speed motors for operational cost savings.

Evaporative coolers are less expensive, more energy efficient, and more environmentally friendly than traditional air conditioning systems. They may be compact or larger, heavy-duty units. They may be portable units on casters that can be moved wherever cool air is needed, or a window mounted type that saves floor space and cools larger areas.


Evaporative coolers are most effective in hot, dry areas, or during the warmest times of the day and when humidity is below 50%. In fact, evaporative coolers are relatively ineffective in warm, humid environments. For example, Mildura’s summertime humidity averages between 20% and 30% which would make the evaporative cooler an effective choice in lieu of a standard air conditioning system.

Evaporative coolers use electricity and water. Actual hourly running costs depend on the unit’s cooling capacity and fan speed. On average:

  • portable units cost $0.02 – $0.03 / hour to run,
  • window-installed or wall-mounted units cost $0.06 – $0.07 / hour to run, and
  • medium-sized ducted units cost $0.12 – $0.28 / hour to run.

Evaporative cooler water consumption depends on the amount of humidity and the fan speed. On average, a portable unit might require 4 liters / hour and a central system might require 25 liters / hour. Water supplies for ducted evaporative coolers must be refreshed, otherwise it can get salty. Different brands and models have varying water management system requirements.

Evaporative Cooler Maintenance

Evaporative coolers generally require very little maintenance. However, regular, basic cleanings and correct appliance shut down and storage can ensure operational efficiency and longer life of the unit. It is generally recommended to clean and disinfect the cooler every six months. Coolers that are in constant operation in hot climates require regular maintenance due sediment, fungus, and mineral build up. Water softeners can assist with mitigating unwanted build up.

The filter pads should be regularly cleaned and replaced twice during the entire cooling season, or as often as once a month during periods of continued operation. Clean the basin inside the cooler so it is free from accumulated dust and pollens that create sludge that can block the pumps, water distribution system, and filter pads.

Window-Mounted Units

The primary maintenance for window-mounted units involves preparing for spring startup and end of season shutdown. In the spring, clean the pump, change the moisture pads, and check the motor oil and add if necessary. When the season is over, drain excess water from the cooler and water supply line, disconnect the water line, unplug the unit from its power supply, and securely cover it.

Portable Units

Portable evaporative cooler filter and water curtains should be cleaned every two weeks. Lukewarm water and a mild detergent are enough to remove dirt, dust, mold, or mildew buildup. Also clean the outer housing periodically with a damp cloth. When the season is over, drain excess water from the water tank, clean the filter and water curtain, and run the fan-only function (if available) for 30 – 60 minutes to completely dry before putting it in storage.