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What is a Swamp Cooler?

By S. Mithra
Updated May 16, 2024
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An alternative to an air conditioner, a swamp cooler uses evaporation, rather than chemical coolants, to lower the temperature of air. People who live in dry, hot climates have long heralded swamp coolers as being effective at cooling and humidifying homes. In ideal conditions, a swamp cooler can reduce the air temperature by about 30 degrees Fahrenheit (17 degrees Celsius).

How it Works

A swamp cooler uses the basic principle of evaporation along with simple technology and electrical power to create cold airflow. First, one motor pumps water into pads of a fibrous, absorbent substance similar to hay, called cellulose. Then another motor powers a fan that pushes air through the pad, which is always full with fresh water.

When the entering air is very hot and very dry, some of the water evaporates into it. Evaporation needs molecular energy, otherwise known as heat, which ends up reducing the temperature of the air and adding humidity. Finally, the cooler air is pushed through a duct into a central location in the building that is being cooled, such as a hallway or main room.


Not only does a swamp cooler lower the temperature of the air, it also makes the atmosphere more pleasant. The chilled air is slightly damper and always freshly recirculated. This gives the swamp cooler many advantages over an air conditioner.

Air conditioners recirculate old air and actually reduce the humidity, which can prove uncomfortable and unhealthy in a dry climate, such as the kind found in a desert region. A moderate degree of humidity in the air keeps a person's mucous membranes moist, thereby increasing those membranes' effectiveness at improving the body's immunity. Also, swamp coolers use significantly less energy, so they conserve electricity when compared with the energy used by air conditioners. Swamp coolers do use more water, though.

Less Useful in Some Climates

A swamp cooler works best when the temperature is more than 80 degrees Fahrenheit (27 degrees Celsius) and the humidity is less than 30 percent. This makes swamp coolers ill-suited for hot and wet climates. The air is already so heavy with humidity in those climates that very little water will evaporate, and the exterior air will be almost the same temperature as the air that already passed through the swamp cooler.

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Discussion Comments
By Edna — On Jul 15, 2012

Could a swamp cooler be damaged if it is run without water?

By anon258978 — On Apr 04, 2012

I had to drink Rick Schlauch Beer and Chips to cool off this summer in Maryland. Oh well.

By anon99505 — On Jul 26, 2010

Trying to find out if a swamp cooler is a good idea in a garage shop containing table saws, band saws, etc.

By anon99383 — On Jul 26, 2010

Yes, swamp coolers are only for hot and dry regions like Las Vegas, the Mojave Desert, Palm Springs, or the entire San Joaquin Valley from Tracy to Bakersfield.

I've been to a lot of homes using these swamp coolers with outside temperature reaching 110 degrees. You'd think they're running air conditioners inside their homes. What's more, it's a lot cheaper on energy costs.

Forget using this in the East Coast. The key here is dry.

By anon97129 — On Jul 18, 2010

Would a swamp cooler be detrimental for a garage with tools i.e. table saws, band saws, etc.?

By anon85925 — On May 22, 2010

Anon- get a small, energy efficient AC for a few rooms. Boston is very humid in almost three seasons.

But if you are as poor as you say you are, get a fan and deal with it.

By anon49738 — On Oct 22, 2009

I don't think Boston would be the best environment for a swamp cooler. Aren't the summers sticky (i.e., humid?) 30 percent humidity is pretty low.

By jabuka — On Jun 14, 2008

anon 14250, went setting on the swamp cooler can be used when you just want to rotate the air, when the temperature is tolerable. In this case the cooler acts as a fan. On very hot days you probably want to use the cool setting, so that the air actually cools off.

By anon14250 — On Jun 12, 2008

what is the difference between high cool setting and high vent setting on my swamp cooler?

By mtcone — On May 15, 2008

Maybe someone can help me here; I do not know much about the topic. I am a college student (Comp Sci, not HVAC) and I would like to try and save some money on my electricity bill this summer. After doing some research I came across this explanation. My problem is, I do not know if a swamp cooler would be the most efficient way to cool a 3 bedroom apartment in Boston. I do not know much about what the humidity is here. You say that swamp coolers don’t work well in some areas because of the humidity. So my question is, do you think that a swamp cooler in a large three bedroom apartment would be a better investment than maybe a portable air conditioner, if I am living in Boston, Ma. If anyone could point me in the right direction, I would appreciate it. I am just a poor student, and every buck I can save helps.

By jabuka — On May 06, 2008

In the hot, dry, semi-dessert of California, I have seen swamp coolers used exclusively, without any additional air conditioning. The swamp cooler actually did a very good job keeping the temperature in the home at a comfortable level.

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