Evaporative cooling

Last updated: 2 December 2022

How do evaporative coolers work?

Evaporative coolers draw hot air from outside through a series of wet filter pads that are supplied with water from a tank at the base of the unit. Water from the filter pads evaporates, drawing heat out of the air and humidifying it. The cooled, moist air is then blown through the house.

Evaporative coolers work partly by cooling the air inside the house and partly by creating a cooling breeze. To work effectively some windows or doors need to be left open so the cooled moist air can be exhausted from the house.

Types of evaporative coolers

Ducted evaporative coolers are available in both standard and inverter models. Inverter models have a variable speed (or inverter-driven) motor, resulting in lower running costs.

Window/wall mounted and portable evaporative coolers are available to cool small rooms or to provide spot cooling.

Ideal conditions for evaporative coolers

As the cooling effect of evaporative systems relies on evaporating moisture from the wet filter pad, they work best in hot, dry conditions. They are not well suited to humid conditions.

If the outside air is humid, the cooling effect of the unit is limited because the water will not evaporate as easily from the pads. As a guide, Melbourne's average humidity on a summer afternoon is between 40 and 50%, while in Mildura it's between 20 and 30%. Both of these areas can use evaporative coolers, although they are more effective in Mildura's drier climate.

Running costs

Evaporative coolers use both electricity and water. Actual running costs will depend on the cooling capacity of the unit and the fan speed that you choose.

Water consumption

Evaporative coolers use both electricity and water. How much water is used depends on the humidity of the day and the fan speed that the unit is set to operate on.

Ducted evaporative coolers must refresh their water supply otherwise it can become too salty, and a range of water management systems are used by different brands/models. If you are purchasing a ducted evaporative cooler, ask about the water management system used and what the typical hourly water consumption is likely to be in your area.

Sizing evaporative coolers

Sizing guidelines for evaporative coolers are based on airflow and the volume of the area to be cooled. It is important to seek an accurate sizing quote from a local retailer or installer who will also consider your local humidity levels.

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