Evaporative cooler is a completely different type of air conditioner that works well in hot, dry climates. It is also known as swamp cooler. Hot outside air enters the swamp cooler. The air passes over water-saturated pads, and the water evaporates into the air. The 15 to 40 degree cooler air is then directed into the home, and pushes warmer air out through windows. When operating an evaporative cooler, windows are opened part way to allow warm indoor air to escape as it is replaced by cooled air. Evaporative coolers use less than one-third the energy of air-conditioners, and cost about half as much to install. It provides a steady stream of fresh air into the house. However, they require more frequent maintenance than refrigerated air-conditioners and they are suitable only for areas with low humidity. An evaporative cooler should have at least two speeds and a vent-only option. During vent-only operation, the water pump does not operate and the outdoor air is not humidified.