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. A portable unit might use up to 4 litres per hour while a central system could use as much as 25 litres per hour.
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.
