Is evaporative cooling any good in Australia?

Evaporative cooling works by passing outside air over wet pads. Water evaporating absorbs heat, so the air comes out cooler and much more humid. That mechanism is the whole story: it depends on the incoming air being dry enough for water to evaporate readily.

Where it works

• Dry inland heat, where the humidity is low and the temperature drop achieved is largest.
• Houses where windows or vents can be left open, since the system needs a continuous path for air to leave.
• Situations where running cost matters more than absolute control, because it uses far less electricity than refrigerated cooling.

Where it does not

• Humid coastal and tropical conditions, where adding moisture to already humid air produces discomfort rather than relief.
• Homes that need to be closed up, for security, allergies, noise or bushfire smoke.
• Any situation needing dehumidification, which evaporative cooling does the opposite of.
• Heating, since it does not provide any.

Maintenance is not optional

Pads, the water tray and the water distribution all need annual attention, and a neglected system develops odour and biological growth in standing water. In hard water areas scale on the pads reduces performance markedly. Systems also need draining or protecting before winter in cold areas.