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Getting an Evaporative Cooler to Work in Humidity

Evaporative coolers don't work in humid conditions, or so people tell you. But you can get them to work and blast cold air even when humidity is high indoors!

All you need to do is understand how these low cost air coolers work and use that knowledge to get more cooling ability from them even when the level of humidity rises to high levels in the room you are trying to stay cool in.

This article will explain how to do that by using the simplest of tricks that you'll probably kick yourself for not realizing after you read it!

Why is the Humidity So High?

First off, it's pretty important to understand why the humidity in your room is rising so high as to stop the evaporative cooler from expelling cold air any more. how to get an evaporative cooler to work in humidityThe explanation is in the way the device works to create cold air.

It uses evaporation of moisture to create the cooling effect, just like your skin does when it perspires in the heat and a breeze feels nice and cool. The appliances have a big water tank that soaks a porous membrane through which air is passed by the fan. The air picks up the moisture and evaporation reduces the temperature rapidly.

That moist air is blasted into the room by the unit's fan so you can enjoy a colder atmosphere. At the same time, all that cool, moist air is saturating the atmosphere in the room, artificially raising its humidity level. Eventually it will reach saturation point (100% humidity) and the evaporation process will no longer work, because the air cannot absorb any more moisture!

Cycle the Air

The way to prevent this happening is simplicity itself. All you have to do is open a window to let in dry air from outside and allow the moist air from inside to cycle out of the room.

You can open a door too. This will create a cross-draft in the room and allow moisture to escape, keeping the room's atmosphere dry enough to allow the swamp cooler to keep creating cold air.

When told about this simple solution, many people are surprised that they should allow hot air from outside to get into the room. Won't that make it hot in the room?

Actually, the room will stay cool because the cooler is still working and blasting out cold air, maintaining a cooler temperature than there would otherwise be in the room. This works very well and if you own a swamp cooler and were concerned it wasn't working properly, please try this before discarding it!

Running Costs are Still Low

This is a big difference from running a portable air conditioner which needs all windows and doors to be closed to keep the coolness in and the heat out. AC still works with a window open, but because it costs so much to run and uses so much power, it would be extremely wasteful (and cost you a lot more in dollar terms) to run AC with a window open.

However, ventless evaporative air coolers cost around 1/20th of a comparable AC to run in terms of power consumption. So there is very little wastage by having a window open and in fact this is actually a necessity to ensure the unit keeps the room cool.

So now you know (if you didn't already). You can run a swamp cooler in a humid room just by allowing air to cycle from outside to keep the moisture level low enough inside and you'll still enjoy all the low cost benefits of this type of cooling process day after day!

In response to a reader's comment, I've included the following note:

Note: This article is intended to explain how to get an evaporative cooler to produce better results indoors when the interior atmosphere's humidity is artificially increased by running the cooler. It is not intended to describe how to make such a cooler work when the exterior atmosphere is also already very humid.

If you live in a really humid place (averaging above 60%), you cannot realistically expect a swamp cooler to work like an AC.

At best you'll get cooler air blown out at you, but it will not cool a room or a whole house as effectively as AC. When the outdoor humidity gets over 70-80%, you'll reach the limitation of a swamp cooler. Then AC becomes the only realistic choice to keep cool.

Update 2020: What About Using a Dehumidifier?

It has been mentioned in the comments that a workaround might be to use a dehumidifier in combination with a swamp cooler to get better cooling in a humid room. Well, to a point, a dehumidifier can improve things by reducing the air humidity in the room and allowing the swamp cooler to cool better.

I must point out that this combo will still not come close to matching the cooling power of an air conditioner.

However, if you already own a swamp cooler and you want to improve its cooling power at least a little, then go ahead and run a dehumidifier in the same room. If the outdoor humidity is high, then run this combo with windows and door closed to allow the dehumidifier to do its work more efficiently.

As long as it can remove more moisture from the air than the swamp cooler adds to the air, you will benefit from a net reduction in humidity and an increase in cooling from the evaporative cooler.

Another important point if you intend using this combo is that a dehumidifier uses electricity too, so your saving on power consumption over an air conditioner will not be as good.

Most medium power, 30 pint dehumidifiers will use around 300 watts of electricity while larger 70 pint units can use around 700 watts. This plus the 100-200 watts of an evaporative cooler still works out to be a lot less than the 1500-2000 watts of 10,000 BTU air conditioner.

You may want to take a look at some dehumidifier suggestions and prices from Amazon by clicking/tapping the link below:

As an Amazon associate I earn from qualifying purchases.


Posted on Sun, May 15 2016 in Air Conditioning | 44 Comments

Last Updated on Sun, Oct 25 2020

Previous Post: Best Value Portable Swamp Coolers to Buy Online

44 thoughts on "Getting an Evaporative Cooler to Work in Humidity"

Todd says:
June 17,2018

Beth, I can sympathize with you for sure! Look it,...if you just want to cool off a single room or small den,...just get an AC unit of nothing less than 13,000 BTUs. A window unit of 14,000 BTU's are equally good but will of course take up more window space.

Yes,...you may end up spending around 4 – 500 bucks, but look at it this way. Once you have your central air back, you can simply store your AC unit and it can be insurance if something else ever occurs with your whole house system.

If you have a ranch home, a good AC unit (window or portable) that puts out at least 15K BTU's can cool more of the house than you think and least make it bearable to survive those humid nights!!


Cook says:
June 4,2018

Hey Beth, an evap cooler + dehumidifier could work, but I think you'll be disappointed at how much cooling you'll get even from a big cooler. If fixing or replacing your central AC is too expensive, a cheaper alternative would be a portable or window AC unit to give you a better level of cooling.

When you add up the cost of a big swamp cooler + a dehumidifier (even a cheap one), you're probably looking at a similar price for a portable AC. Thinking it through, with a portable AC, you'll only need to have a single unit working to give you more coolness and comfort (AC dehumidifies too).

Hope that helps you!

Beth says:
June 3,2018

I live in Florida where humidity is high. Central ac is broken and can't repair right now. Am considering a cooling alternative. Would an evaporative cooler work if I run a dehumidifier same time? Found some reasonably priced dehumidifiers online. All are cheaper than fixing or replacing the central ac right now.

Cook says:
June 3,2018

Hey Allison, anything above about 60% humidity will really impair an evaporative/swamp cooler. At 68%, you'll get a good breeze out of it but it won't feel much cooler than a regular fan.

It is possible to get better performance from a swamp style cooler if the AC is drying the air inside your rooms. That can happen even when it's not cooling much. But you'll need to know what the humidity level indoors is before spending money on buying one. If it's low enough, the AC would take the place of an open window by circulating the air and you might just get enough "cool" out of the cooler to justify the purchase.

A better and maybe even cheaper option would be to find out why the central AC is not performing well. Often it can be something pretty simple, like blocked vents or ducts that doesn't cost much to get fixed. If you're renting, maybe get together with other tenants and present a united front to the owner to get something done about fixing the AC!

Allison says:
June 2, 2018

Live in nj humidity is about 68% have useless central ac rent, no window units allowed would swamp style help bedrooms?

Eddie Smith says:
May 1, 2018

Also, guys, if you have about $100 to spare (and experiment), there are a couple of smaller evaporative coolers on Amazon that are less than $99. They might be worth a test. And I'm not referring to the li'l table-top, as seen on TV models. These are portable, roll around on casters types.

No, they won't cool a large room, but they might be a somewhat better than a basic box fan.

Eddie Smith says:
May 1, 2018

Uhh... guys, you can have windows open with a screen. Frankly, I couldn't imagine not having a screen for my "open" windows.

Also, I got a mini-dehumidifier. It doesn't do as much as a "real" humidifier, but it does get some of the extra humidity out of the air. In fact, before summer, I might get a second one.

Cook says:
April 18, 2018

Terrance, everybody's situation is a little different and it can be tough to give an accurate answer. With Miami's humidity, an evaporative cooler would not be very effective, but if there is AC running to dry the air indoors and expel the extra moisture produced by the cooler, you might get some extra cooling effect. I'd better stress the word "might"…

To be sure in your situation, if you could maybe borrow a cooler from someone and try it to see, that would answer your question and A) provide you with a solution or B) save you buying one for nothing!

If that's not possible, the only way to find out would be (if you can afford it) to go buy one and see. Better still would be to visit your local hardware store and ask there. Someone with local knowledge could give you better advice and may even have experience with something similar to your problem.

I wish I could give you a better answer. Maybe someone else living in FL might chime in.

Terrance says:
April 18, 2018

Living in the Miami area, can I use a Evaporative Cooler in conjunction with my AC unit also running? I have one room in the house that doesn't get cool enough but does get some AC pumped in.

Karen says:
April 13, 2018

Thanks Johnathan! This is just the kind of honest answer I needed! It seems a few people here in Geneva like trying to 'go for the sale' on these evaporation units!

We will continue to look into other options.



Cook says:
June 30,2016

Hi Karen,
At that level of humidity, evaporative coolers would struggle to produce the kind of cooling effect I believe your boss needs. To have any effect, they would also require windows to be open, so the bugs would still get in!

One solution would be to have a dedicated vent installed through the exterior wall of each room to accommodate portable AC vent hoses.

A better solution would be to install mini-split (ductless/zone) AC units in each room. They are more expensive to buy and install, but once they're in, they will cope with high summer heat while helping to reduce humidity inside. They also double as heaters for winter.

Hope that helps,

Karen says:
April 11, 2018

ps I should note that the house is normally very dry inside. 🙂

Karen says:
April 11, 2018

Hi, I am looking for a solution to cool 4 x bedrooms in a large concrete building in Geneva, Switzerland. It gets very hot here from June-August with the humidity being around 64-67%. Normal AC units are a hassle here as the windows are not 'sash' style but open like a book – which makes the hose fitting very annoying and the open window lets the bugs in. My boss (who I'm asking for) HATES bugs!!!

I am wanting your opinion as to whether you think that an evaporative cooler for each bedroom (10-15m sq each) would be of benefit?

Deb Pearl says:
March 12, 2018

My husband and I live in a really humid area, and we were wondering what we can do to have our evaporative cooler work well. Thank you for the tip about opening a window and getting fresh air to cycle into the house. I'm sure that would help with our humidity levels.

Cook says:
March 8, 2018

Atee, if you're quoting the outdoor humidity (75% – 90%) then an evaporative cooler probably won't produce any noticeable cooling even with the room well ventilated. When the air is near to saturation point, it's just not possible to push any more moisture into the air (to create the cooling effect).

To run a dehumidifier will need full voltage so even that, in your situation, may not be a workable solution.

Just an aside, fans only ever blow air at the temperature it is – they never cool it. If you stand in front of a fan then your body produces the cooling effect by your perspiration evaporating in the breeze being produced. However, when the humidity is close to 100% saturation, even your body cannot cool you — in the same way an evaporative cooler cannot produce cool air!

That's why it's so uncomfortable when it's hot and the humidity is very high — regardless of having fans blowing.

Note for everyone reading this: The solution provided in this article was mainly aimed at situations where the indoor humidity has become high but outdoors is lower. If the outdoor humidity is very high, it creates a different set of rules and the process simply cannot be effective.

Atee says:
March 7, 2018

Thanks for your article. I live in Lagos, Nigeria and so the humidity goes way up there from 75 % to 90 % most nights. The voltage being delivered is also crap so the AC's can't work with such low voltage. Now that its quite hot, the fans seem like they are just blowing hot air. I read about mist fans/ evaporative coolers and thought they'd be a nice idea to try and they use less energy than air conditioners. however I'm concerned that with the humidity levels , it will be a total waste of money. Should i stick with a fan or do you thing the cooler could still work f the room is well ventilated? plus is there anyway to both de-humidify the room and use the cooler ?

Eddie Smith says:
September 12, 2017

I live in an apartment, here in L.A. that has no AC. Being that my windows open sideways, like doors, a portable AC unit won't work. I finally broke down an picked up a SPT swamp cooler and I cannot figure out why I didn't think about this years ago. After all, as a kid, we had a old faux woodgrain version of one.

Although a cooler won't lower temps like an actual AC, it can make a substantial difference. When I tell most folks about swamp coolers, they'd never heard of them. If you're in SoCal and heat's a problem, I'd recommend trying out a cheap version of a cooler than doing without one at all.

Ali McFall says:
July 9, 2017

When running a swamp cooler do you need to close the air conditioning vents?

Cook says:
July 10, 2017

Hi Lisa, 60% is around the upper limit for evaporative coolers to be effective so you will still get some cooling from one with a window open. Adding a dehumidifier will help some, but they also consume electricity. In your situation, it would be worth working out the total consumption of each specific model of evap cooler + dehumidifier running together vs that of a portable AC to see which is a better choice on running costs.

Lisa Hayes says:
July 9, 2017

I live in south Orange County, California, about 4 miles from ocean. Today even though the temperature is 83 degrees the humidity is 60% and the dew pt is 63%.

My home was built without A/C in 1970. But it is absolutely miserable here. I was looking into buying a New Air Portable evaporative cooler from Home Depot but now after reading some of your reviews it looks like that might not be smart. With the humidity level as high as it is right now would an evaporative cooler be ineffective? If so would a dehumidifier be a better choice? I know air conditioning would be the best solution but my windows won't hold an air conditioner and the cost of electricity would be too high for me. :/ Any suggestions?

Cook says:
July 10, 2017

Hi Maggie, sorry I didn't respond sooner. I was hoping someone with better specific buildings knowledge might chime in, but I guess not.

From what I know of evaporative coolers, I'd be reluctant to try one on a small enclosed space like you're describing with a total lack of ventilation. An evap + dehumidifier will work but the extra energy costs of specific units together can come close to that of a small 8,000 btu portable AC running on the lowest setting.

The next part would need to be answered by a builder or ventilation engineer, but if it's feasible to ventilate the space maybe with an extractor fan unit installed linking to the outside your options would be better.

Maggie McAuliffe says:
July 4, 2017

I am trying to cool down a "crawl space" inside my daughter's room so that we can turn it in to a little "clubhouse" type nook for her. There is a door to get in to it. There are no windows or vents in the space and it gets really hot in there during the summer. I live in Georgia so obviously it's humid. Would a swamp cooler work if I also purchased a dehumidifier for the space? My only other alternative is to have a dormer window put in but frankly the price for something like that is crazy...

Akosua says:
June 23, 2017

I live in DC where the temp gets up to 100 degrees in July and August. I can't fit a window a/c unit in my basement because of the window bars and no vent because the windows won't hold it. Will the swamp cooler help keep the temperature down?

Skylur says:
June 23, 2017

We live in phoenix. Very hot and dry, even during the rainy season the humidity is rarely above 40 for very long. We are leaving for a trip and having a discussion on leaving the cooler going 24/7 while we are gone or turning on the ac to 86 or so during the day. The whole issue is the dog who will be on guard while we are gone.

The last trip we turned the water off on the cooler and just had the unit come on at night for 5 hours in order to get the cooler air in the house.

Zaak OConan says:
July 23, 2017

There's a good chance it would help. If your AC is dehumidifying the air enough.
Measure the humidity. If 50% or below you will get results from evaporative coolers.

Above 50% your milage will vary.
Higher the humidity goes the less effective evaporative cooling will work.

Kathy says:
May 30, 2017

I live in Southwest MO where the humidity sometimes in summer reaches very high levels. I have AC, but we built on a large 28×24 ft bedroom and only put in 2- 8 in. Vents next to a wall for AC and heat. (my husband was being very cheap) Consequently, it's just not enough to heat or cool the air in that room to a real comfortable level. Since its getting some A.C., would a swamp cooler work here to finish cooling the room to a more comfortable level? Or should we just put in a window unit? Thanks

Todd says:
June 17, 2018

ANthony, I too live in Hot and Humid Memphis and I have an office on the 3rd floor (section of attic that we finished) and basically keep my portable AC on from May until October. It's just a 9,000 BTU unit but does a tremendous job of making it bearable. I keep it running around 10 hours total each day starting at 10am until around 8pm and it really helps. I also have an exercise room in our garage and I have an old 10,000 BTU window unit in there that runs from noon until about 8pm.

Both solutions work flawlessly and my electric bill only gets high in July and August. Worth every penny.

Garage will be around 74 degrees on a 90+ degree day. Office will be about 71 degrees.

From 11pm until at least 10am the office portable AC is essentially off.

Cook says:
April 5, 2017

Anthony, if your AC isn't cooling your bedroom enough, could be it needs to be serviced. You might be better spending that $65 on a service engineer to check over your system, clean out the ducts and get it working the way it should.

Anthony says:
April 5, 2017

I'm in Memphis very humid I have A/C but my bed room does not get as cool as other rooms very hot in peak summer days will a evaporative cooler help my bed room if so what size I priced some from $65 up help THANKS.

Mart says:
January 15, 2017

Hey Louise, I live just outside of Harford CT and I have a free standing swamp cooler in the bedroom. It isn't as powerful as the AC but it does drop the temp about 15 deg in summer when I turn off the AC. Its a little noisy but I like the hum it helps me sleep!

Hey Kalim, that sounds too tech for me, but my own personal experience is a 15 deg drop in temp. It never gets as hot as 120 here in summer!

Louise A Carasone says:
January 14, 2017

I live in Connecticut. Would this type of cooling system work here. I don't have a window in my bedroom, just a sliding glass door. I don't want to be uncomfortable this summer.

Stephanie says:
January 18, 2017

Around 30 degrees or to 90F could be possible with an evaporative cooler. The lower the humidity the better an evaporative cooler will work.

Kalim says:
December 17, 2016

Hi, I have a question if someone can help. If the ambient temperature (DBT) is 120F and relative humidity is 50 %, how much an evaporative cooling will drop the temperature, ie WBT=?

Joe says:
August 30, 2016

A portable AC will do absolutely nothing about the insane heat load inside a closed garage. Even with the unit's vents pointed directly at your bare buttocks.

Cook says:
July 1, 2016

Hey Elsie, If you can close up the garage but have someplace to fit an AC exhaust hose, I'd suggest getting a portable AC and hooking it up. That will cool you down as humidity doesn't affect AC but high humidity will stop a swamp cooler working. AC costs more to run, but what price comfort, right?

Elsie says:
July 1, 2016

Okay, I live in Southern Louisiana, where it is very humid. I'm looking for something to cool my garage. Not necessarily as cool as the inside of my house, but at least something where I can breathe when I sit in my garage. I'm a smoker and do not smoke in my house and sometimes the weather isn't cooperative for me to sit on my back patio (stormy, too hot, etc). I thought something like this would be a solution, but after reading some of the info provided here, I guess this is not the way to go. Any suggestions as to how I can cool it down enough to be bearable??

Tirthanath Goswami says:
June 9, 2017

There r varius types of aircooler in India. Can u suggest the type of cooler best suitable for high humid area, assan,india

Cook says:
June 5, 2018

Brian, thanks for pointing out how you interpreted my article. I'm quite happy to respond.

I actually wrote in the first paragraph: "when humidity is high indoors" to make it plain I was actually describing the effect on the indoor atmosphere. I also wrote, "...open a window to let in dry air from outside" to emphasize the air being drier outside than in.

But I get it. The article headline is intended to grab attention, like all written pieces. Short and catchy but not necessarily misleading. "In Humidity" not: "In a Humid Climate."

The point of writing the article was to give swamp cooler owners a working solution to decreasing cooling with rising humidity levels inside the room being cooled, which I did. Not everyone knows about it, but if it helps some folks, then I'm glad I wrote it.

I pointed this out in an earlier comment reply, but so that others will get to see it, I've added a Note to the end of the article.

Brian says:
June 5, 2018

No you made it sound like you could get them to work even in humid climate.

Prashant Sharma says:
June 5, 2017

Lolss try story ????
And yes unfortunately u cant have it all. These devices are awesome because they cost about ¼ or even less of an AC and electricity consumption is also very low. I mean cost of running an AC increases the electricity consumption to atleast 2 folds if suppose entire house with all the appliance including an evaporation cooler consumes about 500 units of ekectricity a month then using an AC increases it to minimum 1000 or1200 units a month and that too when it is not beings used entire day but in short durations.
So ya no doubt that evaporative coolers are much greener but at the same time they aint as effective as AC
I am from India and have humid sub tropical climate here temperature rises up to extreme 113°F or 45°C and using cooler gives cooling but also increases the inside humidity and eventually the discomforts associated with it.
Coolers are good in month of may and june when there is less humidity outside. In month of July and August we recieve monsoon that is the rainy season that increases humidity to even 80-90 % and unfortunately coolers is of no use then and you cant do anything about it and last resort is to use an AC

Cook says:
December 11, 2016

You're welcome Nathan, glad you took some more time to leave your thoughts.

I'm sure you read through the article and realized it was aimed at why swamp coolers stop working in closed rooms with no way for the rising humidity in the air they create to escape and be replenished with dryer air from outside. Sure there are limits to what these devices can achieve and we can't control the outside climate. But we can to some extent control the indoor climate without AC where it's not insanely humid outside.

One more thing. I lived off grid when I was younger and generated a lot of electricity using a combo of micro-hydro and wind. Photovoltaics were expensive and inefficient back in the 70s (in my day). So we used what we had. Living in a windy place with a pretty fast running river at the far end of the land made it possible to generate a steady 2Kw for a lot of the time. Enough to run a small overhead split A/C unit in the living room where we slept when it got too hot outside.

Times change and technology moves forward. But for all the collected brain power the human race is capable of aiming at a solution to the problem of generating off grid electricity, we've come up woefully short. Or maybe Big Energy is holding out on us because they want us to use the grid power and not get it without paying their exorbitant bills! Maybe I should stop there before I get a visit from some guys in suits…

Nathan says:
December 10, 2016

Thanks for wasting everyone's time. I'm sure everyone that found this article did so because we live in humid areas like the southeast, looking for solutions for off-gridding and such, but have not yet found practical solutions to air conditioning.

Cook says:
June 30,2016

Hey Amy, thanks for the question.

Most of the areas in the southeastern states are very humid in summer and that's not great for evaporative coolers. You need to know the humidity levels in your location to be really sure, but if outside air humidity is 70% or higher I would not recommend using an evaporative cooler, even with windows open.

However, if you already have central AC running in your home and want to cool one room a bit more, they can work because AC dries the air a lot. You would need to keep windows closed in that case and let the AC act as a dehumidifier.

Amy says:
June 30,2016

Will this open window technique work if you live in the southeastern portion of the US, such as northern Mississippi? The outside air is also humid.

Also, what if you have a central air unit but need to keep just one room cooler than the rest of the house at night? Would this unit work, preferably without window open?

Thank you!!