7 Best Sliding Window Air Conditioners (2023 Reviews)

1. Frigidaire FFRS1022R1

Got a bigger room and want to cool it without browsing through dozens of different ACs. If you’re in this situation, Frigidaire FFRS1022R1 will keep you cool without a hassle.

The FFRS1022R1 (try saying that 10 times fast) has plenty of cooling power. With 10,000 BTU, it’s rated for rooms up to 450 square feet but I found that it will keep even much larger spaces at a comfortable temperature.

Like most other ACs on my list, it comes with multiple programmable user modes, including Auto Cool,  Sleep, and Energy Saver mode. There’s also a handy timer function. 

Usability is pretty simple with push buttons on the unit and a remote control. The display and indicator lights are pretty faint and hard to see, though, especially in daylight.

What I do like is the antibacterial filter. I don’t have lab results to prove just how effective it is, but as an asthma sufferer, anything that actively removes outdoor pollutants from the air is welcome in my books.

The filter is washable, so you will save money on replacements. The unit also turns on a (dim) indicator light when the filter needs a rinse.

The FFRS1022R1 is a loud unit. Standing next to it is like standing next to a vacuum. If you’re a light sleeper, I say pick something else for your bedroom.

Also, direct sunlight seems to throw the thermostat off and make the AC run even if the indoor temperature is where it should be. You can compensate by setting the target temperature a bit higher, but it’s good to be aware of the issue.

Despite a couple of design flaws, Frigidaire FFRS1022R1 is a straightforward and powerful AC for horizontally sliding windows.

2. Frigidaire FFRS0822SE 

Maybe you want to cool a smaller room with horizontal sliding windows and the first Frigidaire is complete overkill for you. Frigidaire still has you covered with the FFRS0822SE.

With 8,000 BTU of power, this air conditioner is rated for rooms up to 350 square feet. Like with its bigger brother, I wouldn’t be surprised if it worked decently well for even bigger rooms. It certainly feels like it has what it takes.

Feature-wise, the Frigidaires are practically identical. You get the Energy Saver and Sleep mode, antibacterial and washable filters, timer function, and remote control. Same stuff, just in a smaller package.

The FFRS0822SE does beat its sibling in energy efficiency and noise. It consumes marginally less power and is a little bit quieter. It’s not silent by any means, but if you can sleep with a hotel room air conditioner on, this thing won’t bother you either.

The front panel is pretty much the same as on the bigger unit, so the lights are quite dim. The condensation drain is also positioned weirdly high on the unit, which causes it to collect some water.

Yet, the biggest issue seems to be with the packaging. A lot of people have received a unit that’s damaged right out of the box. Fortunately, Frigidaire sends prompt replacements, but it’s still a hassle.

The unit itself is good and reliable, making it one of the best small horizontally sliding window AC units.

3. Koldfront CAC8000W

Some AC units are notoriously loud. For those who want quiet cooling, the Koldfront CAC8000W is the best window AC unit for side-sliding windows.

The Koldfront is rated for an average noise level of 55 dB — a bit quieter than a regular conversation. In person, though, this is one of the smoothest-operating air conditioners for sliding windows you can find. Case in point, it seems to run only half as loud as the Frigidaires.

This casement air conditioner keeps you nice and chilly, too. Like the Frigidaire FFRS0822SE, it’s rated for 8,000 BTU but punches way above that. Technically intended for 350-square-foot rooms, this AC can keep even a 1,000-square-foot one comfortable.

The Koldfront doesn’t lag behind its competition in features, with an Energy Saver and Sleep mode and remote control. Sadly, there’s no timer, but I’ll forgive that for the unit’s high energy efficiency.

I really appreciate how reliable Koldfront has made this machine. With proper maintenance and installation, it will work for years without issue.

Talking about proper installation, though, that’s a two-person job. This is the single heaviest unit on my list, so you can skip the gym on the day you hoist this beast in place.

Like with the smaller Frigidaire, you might also get a banged-up unit from the start. Koldfront’s customer service is delightfully good, though, so you can get it replaced.

If you’re looking for a quiet AC unit for your bedroom’s horizontally sliding or casement windows, I can recommend the Koldfront. 

4. PerfectAire 3PASC10000

Tired of your sliding window air conditioner racking up your electricity bill? Cooling always comes with a cost, but PerfectAire 3PASC10000’s high energy efficiency can make that pill less bitter to swallow.

With a seasonal EER rating of 13, this is the most energy-efficient unit on my list. With 10,000 BTU of cooling power, comparable to the bigger Frigidaire, it does a great job of keeping large spaces cool without draining your wallet. The unit itself isn’t badly priced, either.

The PerfectAire ships with a complete installation kit, including accordion panels, a support bracket, top rail, and even a screwdriver. Having everything in one package makes the heavy unit easier to install. I just wish the instructions were better — be prepared to use your imagination at some points.

Like the Frigidaire models, the PerfectAire has washable filters, which saves you more money on maintenance. The other features are there too — four fan speeds, filter indicator, Sleep and Energy Saver mode…

I think all these manufacturers might actually use the same control panel.

PerfectAire does have one unique feature I like — the Follow Me thermostat. The thermostat is embedded in the remote control and automatically sets the AC based on where the thermostat is. You can always stay cool, as long as you remember to keep the remote with you.

Although this is a sliding and casement window AC, it can also work with narrow double-hung windows. If you have an old home with narrow windows of any kind, this might just be the unit for you.

PerfectAire is loud, though, so I wouldn’t put it in the bedroom. But hey, maybe the energy savings will help you sleep better.

5. Keystone ‎KSTAW08A

There is no one-size-fits-all solution when it comes to air conditioners. Yet, Keystone KSTAW08A comes about as close as you can get to a unit that fits almost any window opening.

Now, it’s not designed for wide horizontal windows — for those you still need a standard window air conditioner. Otherwise, you should be all set.

On top of casement and vertical windows (that slide horizontally), the Keystone unit fits narrow vertical-sliding windows, like the PerfectAire. It also has a removable chassis, which makes it relatively easy to install even as a through-wall air conditioner.

With an 8,000 BTU rating, the Keystone matches the Koldfront and smaller Frigidaire air conditioners in power. It turns small- to medium-sized rooms basically into refrigerators. Although it’s not quite as quiet as the Koldfront, Keystone is not a loud window air conditioner. 

Unlike the Koldfront, though, Keystone has a full gamut of features, including a timer. You can control the three cooling speeds, dehumidifier, Energy Saver, and Sleep mode with the simple-to-use, responsive remote control.

As a nice touch, this vertical window AC unit is a bit lighter than most others on this list (though it's definitely heavier than the claimed 30.3 lbs). Installing it is still a two-person job, but every pound shed off the unit makes the process easier.

I’m not too impressed by the high-ish energy consumption, which is about on par with the small Frigidaire unit. An EER rating of 10.8 is just pretty sub-standard these days.

Yet, for those who need a window AC unit that can go in a horizontally sliding, a narrow double-hung, and a crank window, Keystone can bring you that versatility.

6. Homelabs

I’ve listed a lot of vertical air conditioners so far — but what if your home has perfectly regular double-hung windows? Well, then the Homelabs 6,000 BTU is the best air conditioner for you.

As its name says, this window air conditioner is rated for 6,000 BTU, making it the weakest unit on my list. Yet, the numbers don’t tell the whole truth. The box says it’s for rooms up to 250 sq-ft, but this AC can handle spaces even triple that.

The unit comes with a rather lousy remote controller. That’s fine, though, because it’s Wi-Fi connectible and can pair with your smartphone — or Alexa. Combine that with the Follow Me function (like the one on PerfectAire) and you have one of the easiest-to-control window air conditioners.

This machine is lightweight and compact, so installing it is easier than the vertical window air conditioners. You don’t get a support bracket in the box, though, so you’ll have to either buy a separate one or rig up a stick-in-the-ground solution.

I appreciate the low energy consumption, with an Energy Star brand to prove it. Together with the low price of the unit itself, Homelabs can provide affordable cooling for your home.

For all the good things I’ve said about this AC, there’s one huge design flaw — there are no drainage holes! Condensation will quickly build up in the casing, which could lead to mold or leaks. You can easily drill a small drainage hole yourself, but I can’t recommend doing that if you care about the warranty.

Homelabs also has higher BTU models, ranging from 6000-14500 BTU.

View more Homelabs AC Units.

7. TOSOT Aovia GPC05AP

Not everyone can or wants to install a stationary window air conditioner. If you’re in this crowd, the Tosot Aovia portable air conditioner can still supply you with cool air.

The Aovia works with both vertically and horizontally opening slider windows. The window panel for the duct can extend from 9” to 62”, which makes it fit practically any window. You can even attach it to a casement window if you have something to block the remaining openings.

In terms of power and features, this portable air conditioner doesn’t pale in comparison to any stationary units I’ve listed. It matches the Keystone and Koldfront units in BTU, although it can’t go over its 250-square-foot coverage rating, unlike those units.

It also has a timer and a dehumidifier, three fan speeds, and a Sleep mode. In other words, the Aovia is a full-fledged window air conditioner. I wish it had an Energy Saver mode since this unit has the lower energy efficiency rating on my list. Then again, portable air conditioners will never beat stationary ones in this department. 

My biggest issue with portable air conditioners is drainage, but the Aovia resolves that problem with an auto-evaporation function. Unless you live in an extremely humid area, the AC disperses all condensation to keep its running parts cool. Less maintenance, more cooling!

The thermostat isn’t the most accurate, so the device can cycle on and off seemingly whenever it feels like it. You can try to mitigate that by turning the temperature setting up or down.