Is a Swamp Cooler the Best
Outdoor Cooling Solution for
Your Area and Your Needs?
If your weather is hot and dry, a swamp cooler can be a great outdoor cooling solution for you.
"Swamp coolers" combine wind and water in an enclosed unit. They are a kind of evaporative cooler, also called "air coolers" or "desert coolers." They use a fan to either pull or push warm air through a water soaked pad. All evaporative coolers provide more cooling in hotter, drier weather.
They need electricity and water, so you might want to read about their water and energy use. Take a look at our other pages to learn about sizing, parts, features, costs and more.
Are these the best choice for YOU? That depends on your needs, your weather, your energy supply, budget, etc. The more you understand your needs and the more you know about your options, the better choices you'll make. We have a page where you can compare basic aspects of different outdoor cooling methods. Or read about them in detail on the pages devoted to each cooling method.
How, When and Where They Work Best
On a hot day, when warm air comes in contact with water, it makes the water evaporate. When the water evaporates, it cools the air immediately around it. (If you've ever felt cold when you step out of a shower or pool, it's because of the evaporative cooling effect.) Swamp coolers then blow out this cool air, cooling an area by anywhere from 3°F / 1.5°C to as much as 30°F / 16.5°C, depending on the humidity and the air temperature.
Swamp coolers actually work best in the hottest, driest part of the day.
Humidity is often called "relative humidity," or "RH" because how much water the air can hold is relative to how hot it is. Hotter air can hold more moisture than cooler air. A level of moisture in cool air may measure 40% RH, but as the sun rises and the air temperature increases, that same amount of moisture might be measured as 30% RH.
Since evaporative coolers work by evaporation, they tend to add more moisture to the air. Air that already has a lot of moisture in it can't hold much more of the cool moist air that comes from a swamp cooler; air that is naturally dry can absorb more of this cool humid air. Also, air that is naturally humid in the morning will be able to absorb more of this additional cool moisture as the sun rises in the sky and the air gets hotter.
Heat causes the evaporation that cools us. Swamp coolers use the heat from the outside air to trigger that evaporation. So high temperatures with low humidity are the best conditions for a swamp cooler.
To learn more about how weather affects the cooling capacity of evaporative coolers, go to our weather page. There you'll also find a link to a site that can give you the average temperature and relative humidity levels for your area.
Compare the numbers for your area with the numbers on the following chart. This chart shows how much cooling you can expect from evaporative coolers based on air temperature and relative humidity.
Not noted in this chart is the additional 4 - 8° F / 2 - 4.5° C of cooling from the breeze a swamp cooler creates. They move a lot of air, much like outdoor fans. So in addition to cooling from evaporation, you'll feel some extra cooling from the fan.
In fact, many swamp coolers have a feature that lets you turn off the evaporation function and use the fan only -- for ventilation or mild cooling in the most humid environments. In more humid weather you will feel less cooling from the evaporation, but you'll still feel the cooling breeze from the fan.
