Can You Run a Swamp Cooler Without Water?

In drier climates during the summer, an evaporative cooler, also known as a “swamp cooler,” can offer you not only relief from the heat, but also from a lack of humidity. Using water to cool the hot air that passes through, they can drop the temperature in a room by 15º to 40º. If you are new to swamp coolers, you may have some questions.

Can you run a swamp cooler without water? It’s not advisable to run a swamp cooler without water. For starters, it will not effectively cool the room; it will only circulate hot air. But also, running a swamp cooler without water may cause the motor to burn out. It’s more effective to just use a fan instead.

To better understand how to operate your swamp cooler for maximum comfort and efficiency, let’s look at how they work, why they need water, what climates are best for using them, and what types of evaporative coolers are available.

How Does a Swamp Cooler Work?

When you turn on your swamp cooler, the pump will draw water up through the coils and deposit it into the filtration pads. A fan then pulls hot air from outside the house through the damp pads, filtering and cooling it before pushing it into the room. As the room fills with humid, cool air, the dry, warm air is displaced and must escape through a vent or a slightly ajar window. 

In the case of a portable swamp cooler, the warm air of the room is drawn in the back, through the moistened evaporative pads, and then pushed out the front into the room. While this does not necessarily provide the room with fresh air, like a mounted evaporative cooler would, it does help by recirculating filtered air back into the room. 

An evaporative cooler that has been installed permanently into your home may be able to draw water from a line that taps directly into your home’s water system. However, portable swamp coolers and some other models require that you refill the reservoir with filtered water regularly

There will be a float gauge in most coolers that turns off the pump when the water level gets too low. This helps to prevent motor burn out, but it also saves energy.

Why a Swamp Cooler Needs Water

So, really, why is it important to have water in your swamp cooler? We’ve already talked about how a lack of water basically renders your cooler useless. Why won’t it work without water, though? 

We’ve covered some of the nuts-and-bolts of how swamp coolers operate, but let’s look at it from a more scientific perspective. 

You know how it feels when you exercise and sweat, and then a cool breeze hits the sweat, so you are instantly cold? The principle is very similar here. 

  • The hot air is brought into the pads of the swamp cooler to provide it with “sweat” (the water in the pads). 
  • Then, the fan creates the breeze to drop the temperature. 
  • The heat plus the breeze further work together to vaporize the water in the pads creating the effect of humidity in the air.

None of this would work without water, because the hot air would not have a catalyst to cool down

Instead, what would happen would be hot air being drawn in and blown out by a fan. That’s it. There would be no filtering or cooling stage. The air that would blow out might be a degree or two cooler because it’s being fanned out, but really, there wouldn’t be too much of a difference.

Need Proof?

The water is an integral part of what makes a swamp cooler different from a box fan. If you need to see this for yourself, you can perform this experiment using items you’re really familiar with. 

  • On a hot day, set up a box fan and place a damp hand towel on the back. 
  • As the fan sucks the hot air from the back through the damp towel, the air that comes through on the other side will be much cooler than if you remove the towel altogether. 

Please note that this is a suggestion for a short experiment to illustrate how a swamp cooler works, and it is not meant as a way to use your box fan repeatedly. Constant moisture applied to a box fan will damage the motor.

The Best Climate for a Swamp Cooler

It should go without saying that some climates are more humid than others. 

If you’ve ever spent a summer in the southern United States, you’re familiar with the sticky, muggy, fog that descends with the heat. It’s wildly uncomfortable, but it also makes for a bad environment for a swamp cooler. 

They already have enough swampiness already. But additionally, the excess moisture in the air makes it harder for the water in the pads to evaporate to cool the air. For that reason, it’s better to use a standard air conditioner and possibly a dehumidifier if you live in a humid climate.

However, desert states like Nevada, Utah, and Arizona are great candidates for swamp coolers because they are arid. The additional humidity provided by a swamp cooler is a relief. Also, the lack of moisture in the air allows the water-dampened pads more availability to vaporize and cool the air. 

Something to consider, though, is that in places like Arizona where temperatures can reach well over 100ºF, you may still need a refrigerant-based air conditioning system in addition to your evaporative cooler to drive the temperature low enough. 

It’s estimated that an appropriately sized swamp cooler can drop the temperature of a room in Phoenix by 15º. This is not going to feel like much, though, on the hottest of desert days.

Four Types of Swamp Coolers

So, if you’re living in a desert area and feel that you could benefit from a swamp cooler, and you’re not worried about the water you’ll need to run it, there are four types to choose from.


A portable swamp cooler (click to see on Amazon) won’t take up too much room but can be used for one specific room that needs help. This is great if you just want to cool off the garage, workshop, or small outbuilding during the warmer months of the year. Different models offer adequate cooling power for all sizes of rooms, though, so make sure to check the specifications before you buy one. 

Window Mounted

Window units look very similar to their air conditioning counterparts and function just about as well but on less energy. The benefit of a window-mounted swamp cooler is that it is easy to install on your own. You can remove it easily when you no longer need it. However, the downside is that, like any window shaker, it will only sufficiently cool one or two rooms, not the whole house.


Roof-mounted options will require an air conditioning service to install it for you. These are much more efficient for whole-home cooling. However, it’s important that your unit gets shade; otherwise it will not work as well. Also, there is a risk of water damage to your roof, and they are harder to maintain.


A grounded swamp cooler is great because it can efficiently cool your home. It’s easy to get to for maintenance. Again, it’ll be important to install this unit in a shady spot, though, for optimum efficiency.

Wrapping It Up

If you live in an arid climate, you should consider the efficiency of a swamp cooler to provide you with humidity as well as nicer temperatures. However, remember that you will need water to run your swamp cooler in order to get the best results from it.

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