An evaporative air cooler uses evaporation – the conversion of water into water vapor – to fan out a cool breeze and lower air temperatures. Its cooling power is more robust than a standard fan, yet it still consumes minimal energy. Evaporative air coolers are also known as swamp coolers, desert coolers or wet air coolers, and are most effective in hot, dry climates. The sensation is like a lakeside breeze—a cool wind with a hint of moistness.