The Benefits of Evaporative Coolers

A low cost and viable alternative to air conditioning for people who live in areas where the summer heat is relatively dry are evaporative coolers.

These non-refrigerant cooling devices, often mistakenly called ventless portable air conditioners, have several benefits over AC that I will explain in this article.

The main reason many people choose these evaporating swamp coolers as their summer solution to the heat is the much lower running costs.

This is coupled with very low energy consumption which is very attractive to environmentally aware people who are concerned about conserving our natural resources, which includes the high cost in ecological terms of generating grid electricity.

Why Are Evaporative Coolers So Much Cheaper than AC?

evaporative coolerThe main reason for the low running costs and frugal electricity consumption lies in the way that these devices produce chilled air that is output from their front grills.

Instead of employing a refrigeration process as do AC units, which is very energy hungry as well as wasteful as it produces a lot of heated air as well as chilled, evaporative coolers use the much simpler process of evaporating moisture to create a chilling effect.

This works very much like the way in which your skin feels cool when you perspire and a breeze passes across it. The perspiration is evaporated by the breeze and that lowers the temperature of the air, which your skin feels as a cooling effect.

Water Reservior

In the cooling units, a reservoir of water is maintained at the base. That water is soaked into a porous membrane that is stretched over a vertical frame.

A powerful fan blows air through the membrane evaporating the water quickly, creating a chilled wind that blows out of the front of the unit.

The simplicity of the process and the lack of motorization and moving parts means the only part that uses any appreciable amount of electricity is the fan. This is generally in the 50-100 watts area.

When you compare that to the 1-2 kilowatt or greater consumption needs of a comparable portable air conditioner, you can easily see what a huge saving in energy costs this mode of cooling provides as a major benefit.

What Are the Disadvantages of Swamp Coolers?

There is one major and rather unfortunate drawback that mars the wonderful economy benefits of this type of cooling device. It has everything to do with the way it creates chilled air and there is little that can be done to overcome the problem.

That problem is humidity. A swamp cooler's effectiveness is reduced as the level of humidity rises. Anything past 50-60% humidity and the unit's effectiveness is so curtailed that it is little more use than a regular fan.

The reason for this is simple to understand. The air can hold a certain amount of moisture, which we can measure as its level of humidity. This ranges from zero, or completely dry air (this is only really repeatable in laboratory conditions) right up to 100% which is fully saturated air.


In very humid climates where there is a lot of rainfall or moist air during hot weather, it is more common than you might think to experience 100% humidity.

In this situation, it becomes highly uncomfortable because no matter how much you perspire, the breeze will not cool your skin. That's because the air cannot hold any more moisture so your perspiration does not evaporate!

This is what happens to a swamp cooler in the same damp conditions. It simply cannot get any more moisture into the saturated air and so there is no cooling effect.

It often happens that people buy a swamp cooler because they cannot afford to buy and run an AC unit, but they fail to understand this point about humidity. If they get lucky and just happen to live in a dry air climate, such as in the dessert or similar, all is fine and they can enjoy cheap cooling.

However, what happens more often is the purchaser lives in an area with high moisture levels during summer and they don't get any cooling effect from the unit. They complain that "these things don't work" and return them to the store.

A little research and education prior to making the purchase would save a lot of hassle and bad feeling.

Artificial Humidity

Another problem some users come across is despite living in a low moisture climate, they still have problems with the cooler not producing any cool air indoors. What happens is they run the cooler like they would an air conditioner - with all the doors and windows closed to keep the heat out and the coolness in.

The problem with that is by trapping the air inside, the cooler will keep blowing cool, moist air into the space, gradually raising the indoor humidity level until it reaches saturation point, where it will no longer produce any more cold air. In many situations, by the time that happens, it has probably already cooled down so much ion the room that the user would turn off the unit anyway.

Open Window

However, this problem can easily be overcome by simply cracking open a window or two to create a through draft that will cycle dry air from outside and lower the humidity inside.

You needn't be concerned that you'll be letting the heat in and wasting energy. That's because swamp coolers use so little electricity anyway, this is a very small wastage to have continuous cooling.

Of course, this is not a problem when the unit is used outdoors. Of course many summer poolside parties and family gatherings on the terrace can be made much more comfortable by running a swamp cooler to blow cool air at the occupants!


If you're looking for a cheap solution to suffering in the heat of summer in your location, make sure you are aware of the general or predominant humidity levels during the hot weather before you decide to buy a swamp (evaporative) cooler.

If your local weather station tells you that the humidity is high in summer, you'll need to rethink your options and maybe accept the higher cost of an air conditioner for the sake of getting some cool comfort when it gets too hot to do anything. See for more information and comparisons.

A slightly more economical portable cooling solution for high humidity areas is a fully self evaporating air conditioner that is fitted with dual hose venting. However, these are still air conditioners and use a lot of power to keep you cool.

If, on the other hand your local weather has predominantly low moisture air, you're in luck because you can save money on energy bills, as you're good to go with a swamp cooler or two!

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