Evaporative coolers consume 1/3-1/4 of the electricity of central air conditioners and cost about a 1/3 or less. They are an efficient option, though their use is in decline.
They perform badly in high-humidity conditions and have significant cleaning and maintenance requirements, besides consuming a lot of water.
Evaporative coolers cool quickly and are healthier than air conditioners, but besides being useless in humid weather conditions they require monthly routine maintenance and adequate venting, often done through open windows or dedicated outlets. An evaporative/swamp cooler is a box-like frame with a water pump and a motor that drives a big fan. The fan captures and forces outdoor air through water-soaked pads, filtering and cooling the air before driving it into the home (causing warmer inside air to be pushed out through windows or vents…).
They only work well when the Dew point temperature is below 55ºF.
Be aware. Evaporative coolers, whatever their type, do not make sense in energy-efficient homes in cold and moderate climates, or in hot-wet climates.
Low-energy buildings rely on very high levels of insulation and sealing, and in small heating and cooling HAVC systems.
There are now portable evaporative coolers, for moderate climates, able to cool a room. Customer reviews and ratings of these low-capacity coolers are very mixed.
There are also window evaporative coolers, easy to mount and with a wide set of designs and goals. They can cool small homes, or just rooms…
Mobile evaporative coolers are a category apart. They are designed to cool large opened spaces (garages, warehouses) or out-of-door spaces, taking advantage of the low running costs of evaporative cooling. They are very powerful units with high prices. They do not make sense from an efficient standpoint.
An evaporative cooler (or swamp cooler) cools by moving air and, most of all, by using water to cool indoor air.
The other type of evaporative coolers – central evaporative coolers – can be mounted outside home, on a wall or on the ground, or in a central part of the house, typically on the roof. They are the most typical and traditional type of evaporative coolers, and can be ducted or un-ducted.
Our video on Evaporative Coolers
A too big unit – or insufficient ventilation - will cause too much humidity in the house. A too small unit will not provide enough cooling – a very common problem to small portables. In other words: sizing and venting a evaporative cooler is critical.
Evaporative coolers are also great as ventilation fans (make sure that they have a vent-only option). A central unit with a vent-only option can perform as a whole-house fan, by bringing outside breezes and fresh air into the house. Similarly, a window evaporative cooler can function as a window fan, also bringing in outside breezes. That’s an important feature for energy-performance.
If buying, consider also a unit with a thermostat, filters and with at least two fan speeds. That's also critical for efficiency.
Electricity and water consumption
Evaporative coolers are electrically powered, and consume about one fourth to one tenth of the electricity of conventional air conditioners. Evaporative coolers also consume water: very little in the case of portables, and between 4 and 10 gallons (15-40 liters) per hour of operation, for central units. Evaporative coolers are useless during humid weather, which prompts us to question their role in moderate and hot climates with periods of both dry and humid weather.
Are they worthwhile in that case? Can they be used in conjunction with air conditioners and fans, and shade strategies?
See on these issues: Evaporative coolers, AC and Fans
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