A Swamp Cooler Could Be Your Hot Weather Saving Grace — Here’s How to Use It, According to Pros

When discussing oppressive summer weather, you’ve probably heard the phrase “it’s not the heat, it’s the humidity.” That’s because humidity that’s too high can prevent sweat — your body’s natural cooling mechanism — from evaporating, making you feel even hotter. That’s why so many air-conditioning units focus not just on cooling the air but also on reducing the humidity. But moisture in the air isn’t always a bad thing in summertime. In fact, in hot and dry climates, moisture in the air can be your friend — and that’s the philosophy behind swamp coolers, also known as evaporative coolers.

The name “swamp cooler” makes it sound like an appliance used by creatures of the deep, but these coolers actually harness the power of evaporating water to help people stay cool in hot, dry climates. (In fact, the technique that makes swamp coolers work dates back to ancient Egypt when wet reeds helped folks beat the heat. Times have changed, but the principles have stayed the same. Here’s what you need to know about swamp coolers and whether buying one is a smart choice for your home.

While most whole-home and window-unit air conditioners use a refrigerant for cooling air, swamp coolers use the natural water cycle. “Swamp coolers are an energy-efficient cooling system that uses the natural process of water evaporation to cool air,” says Steve Robbins, the owner of Robbins Heating & Air Conditioning in New Mexico. 

Swamp coolers, or evaporative coolers, use a system in which water changes states from liquid to gas in rapidly moving air to help cool spaces. “Swamp coolers operate on the principle of evaporative cooling,” Robbins adds. If you’ve ever felt water evaporate off your skin, say after a shower or swim, there is a slight cooling effect, and swamp coolers use this to their advantage.

Swamp coolers work more or less the same in smaller portable sizes as they do in large, whole-home sizes.

According to Robbins, a swamp cooler draws in hot air from outside and passes it through pads saturated with water. “As the air moves through these wet pads, the water evaporates, absorbing heat from the air and cooling it down,” he says. Next, a fan circulates the cooled, hydrated air. The process of evaporation combined with moving air can reduce indoor temperatures by 15 to 40 degrees, depending on outdoor conditions.

Joshua Owens, a commercial HVAC/R technician with The Chatty Tech, dives deeper into the cooling process. He says that for whole-home swamp coolers, a mesh blanket surrounds the fan, and water is pumped to the top of the mesh. The water then succumbs to gravity while saturating and soaking into the blanket. “At the same time, the fan is pulling air through it, causing some of the water to evaporate and lower the temperature,” he adds.

Although you may be considering purchasing a swamp cooler — after all, the premise of using water over a refrigerant is appealing — it may not be the best idea if you live in an already humid place.

“I would not recommend swamp coolers for humid climates or tightly sealed homes without proper ventilation,” Robbins advises.

Because air in humid environments is holding moisture, you won’t feel the cooling effect of evaporation because the air is already saturated.

Suppose you live in a hot, dry climate, such as in the Southwestern United States, as Robbins does. In that case, he says that swamp coolers are ideal for workshops, garages, single-family homes, and industrial spaces, such as warehouses. You can also place them in an outdoor area like a patio or deck to get relief from the extreme heat. 

Humidity is a significant factor with swamp coolers, so Owens says people don’t use them in tropical climates like Florida. “As humidity goes up, the amount of degrees they can drop is affected dramatically,” he says. For example, in 100-degree weather, if the humidity is 0%, a swamp cooler can lower the temperature to 70 degrees. In contrast, it can only cool to about 80 degrees if the humidity is 30% outside. 

Fortunately, swamp coolers are readily available at home improvement stores, manufacturer websites, HVAC supply stores, and online retailers like Amazon and Wayfair. “Just do your research before you buy so you get the right size for your house,” Robbins recommends.

He and Owens suggest contacting an HVAC professional if you need one for your entire house. “These are often permanent installs and generally installed on the roof as a downdraft,” adds Owens.

Owens has several favorites, although depending on the application, he’s loyal to two brands: Hessaire for portable units and Master Cool for whole home units.  Robbins recommends the Aerocool Trophy series for small spaces and the Pro series for larger areas. 

Here are a few specific swamp coolers our experts recommend.