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Ask G: Evaporative air conditioners

Evaporative air conditioners save you electricity, but what about the water use?

We want to cool our house without guzzling huge amounts of electricity. I've heard that evaporative air conditioners use less energy than refrigerated air conditioning. But that means adding to our water use to reduce our energy use. How much of a trade-off is it? How much water do evaporative coolers use?

Felicity, SA

Water splash

Cool down: is the water use with evaporative air conditioners worth it?

Credit: Everystockphoto

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It's a cruel irony, but evaporative coolers work best in hot dry climates where people are probably looking for ways to save water rather than more ways to use it.

However, the energy savings are substantial, with evaporative coolers using around a fifth of the electricity used by the equivalent refrigerative air conditioner.

Water consumption starts from about 4 litres per hour for small portable units and up to 15 to 30 litres per hour for ducted whole-house systems.