The Best Sliding Window AC Units: 2019 Buyers Guide

A slider, or casement, air conditioner is what you would look for if you need to fit an AC into a sliding window. Not every air conditioner is going to fit into a sliding window. The ones that fit in such windows have a vertical orientation and are longer than a traditional window air-conditioner.

Casement ACs start from 20 inches in height and above. They come with precut inserts and fasteners that can hold the AC unit in the window frame. While serving to help your unit stay in place, they also eliminate the hassle of buying and installing styrofoam or plexiglass to block any open space.

Sliding Window AC Comparison Chart

PRODUCT DETAILS
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Frigidaire FFRA0511R1 5,000 BTU 115V Window-Mounted Mini-Compact Air Conditioner

  • Comes With Two Cool Speeds and Two Fan Speeds
  • Our Best Overall Choice for Sliding Window AC Units
  • Quick and Easy to Install (Less Than Twenty Minutes)
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Frigidaire 5,000 BTU 115V Window-Mounted Mini-Compact Air Conditioner w/ Mechanical Controls

  • Mechanical Controls Make it Easy to Operate
  • Vents Can Be Adjusted to Cool in Any Direction
  • Durable and Can Stand Up to Even Constant Use
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Global Industrial Casement Window AC

  • Covers around 450 sq ft
  • Full installation kit
  • Four-way air direction control
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Frigidaire FFRS1022R1

  • Dehumidifies 3.4 Pints Per Hour
  • EER 10.4
  • Designed for both sliding and casement windows
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Kool King Slider AC

  • Four-way air directional control
  • Controlled via remote
  • Three fan and cooling speeds
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Arctic King AC

  • 10.9 EER
  • Controlled via remote
  • Comes with full installation kit
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LG Energy Star Window Air Conditioner

  • Fan has a Large Amount of Blowing Power
  • Energy Efficient, Will Work During Low Power Periods
  • Can Be Controlled Through Multiple Methods, Including Remote and WiFi
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Frigidaire FRA052XT7

  • Two-way air direction
  • Anti-bacterial filter
  • EER 9.7
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Keystone 5,000 BTU 115V Window-Mounted Air Conditioner

  • Will Not Bump Up Your Electricity Bill
  • Lighting on the Unit’s Face Can Be Turned Off
  • Able to Cool Even Oddly-Shaped Rooms
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hOmeLabs 5000 BTU Window Mounted Air Conditioner

  • Quickly Cools Rooms, Even When on Low
  • Our Best Sliding Window AC for the Money
  • Awesome at Removing Humidity From a Room
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Aspects to Consider When Buying a Vertical Sliding Window AC

There are a number of qualities to consider when seeking out a vertical sliding window AC. The first, of course, is cooling effectiveness. You can hit it out of the park on every other important aspect of a window AC, but if it does not cool the way you need it to, what is the point?

What you are going to need to keep in mind here is the size of the space you are trying to cool. Is it just the room the air conditioner itself is in, like a bedroom? Is it a room that connects to another room, like a combined living room/kitchen space? Is it a whole floor? The larger the space, the higher the BTUs (British Thermal Units) you will need.

Beyond a unit’s cooling capacity, you also need to think about the way it will fit into your window. It is important to consider how much space your sliding window can provide for your air conditioner and to make sure the unit you purchase will fit in the available window dimensions. However, it is not just about dimensions when it comes to sliding window ACs – you also need to consider how heavy the unit will be. A heavier AC can make for a more complicated installation process that you likely will not be able to get done all on your own, and may also require additional external support to hold your unit in place.

Advantages and Disadvantages to Vertical Window Air Conditioners

Vertical window air conditioners have a number of awesome qualities, but, as with any air conditioning unit, there are definitely also some drawbacks. Here are the most noticeable pros and cons:

Pros 

It can be pretty difficult to beat vertical window air conditioners when it comes to renting a home or apartment without a central AC system. Obviously, installing central AC in such a circumstance is not an option, and window units are one of the most affordable ways to prevent roasting inside your place of living every summer. 

They are also extremely customizable, so it will be simple for you to find a vertical window AC that fits your needs in terms of window size and location, and also provides you some handy features, such as remote control, WiFi, or temperature sensing ability. And, because these units are installed in windows, you will not have to worry about rigging up some complicated new electrical and hose system the way you would need to do with a standing indoor AC unit – the water for these systems can just drain right out the window itself!

Frigidaire FFRS1022R1

Cons​

Vertical window air conditioners are not exactly the most attractive element of a home décor system. It is pretty hard to sugarcoat how bulky and just straight up ugly these units can be. Of course, that is a pretty small price to pay when it comes to being cool and comfortable, and you can always remove the AC unit when it is not the peak of summer.

However, that leads to another potential con – these units can be heavy and complicated to install, so uninstalling and reinstalling may not be the most viable option for a lot of folks. Another thing to consider is that a window AC unit requires actual insertion into your window, which means your window needs to be opened to a certain extent. This can allow hot, humid outdoor air to pour in and cool air to escape. It also leaves your home more vulnerable. You can mitigate this with insulation and other sealing, but you can’t really get around the fact that on some level, this makes your home less secure.

Horizontal vs. Vertical Window AC

You may be wondering why on earth vertical window ACs are even a thing, when most sliding windows tend to slide up and down, not to the left or right. Wouldn’t a horizontal window unit make more sense in such a sliding window situation? The answer is simple: gravity will exert a different kind of pressure on a window unit that is placed in a horizontally-opening window than one that is placed in a vertically-opening window (for this reason, most newer homes are actually moving away from the horizontally sliding window model and incorporating more vertically sliding window systems).

Think about it: an air conditioning unit that is installed in a vertically sliding window has much more support on either side to hold it in place. An air conditioner installed in a horizontally sliding window does not have that support, and as a result, it tends to tip outward. In order to prevent this, you would either need a unit that substantially protrudes into the room, which is not exactly ideal, or you would need a block of wood or some other type of support system on the outside of the window, which may not be a viable option if you are installing your unit on the second story (where most bedrooms tend to be!).

You can see that a vertical window AC unit makes far more sense. Of course, if you happen to have windows that slide horizontally instead of vertically, you will not have a choice in the matter. But if you have the option of picking between a vertically sliding window and a horizontally sliding window, you should always go with the vertical one.

The Unique Challenge of Sliding Windows

Unlike a traditional window, a sliding window works from left to right. Side-by-side casement sliders slide conflict with each other - you usually can’t open both sides at the same time.

The sashes of these windows do not allow a traditional window AC to fit into it. Because of this, a normal AC would leave a lot of space at the top. This brings down the efficiency of the AC or makes you add other fitting work to cover the space. Also, most AC units will be too wide for the typical casement window.

Sliding windows come in standard sizes. Measure the size of your window before purchasing an AC unit. The size also influences the power outlet. Larger casement air conditioners require an independent 230-volt circuit and not the normal household 110-volt.

Like any window unit, a casement AC performs best when its rear side is in a shady place. So the best choice is to use it in a window where there is some shade - a tree, overhang or even plants or shrubs can help, as long as they aren’t too close.

A metal frame is usually installed first to support the AC unit. This helps protect the window frame and provide extra support to the AC unit itself, preventing it from putting a lot of weight on the sill and window jambs.

Basics of Cooling Potential

Each AC unit has the potential to cool a space based on its BTU rating. BTU, or British Thermal Units, indicates the amount of heat that can be removed from a room. A larger BTU rating on an air conditioner means it can cool larger rooms.

Casement air conditioners come with a maximum of 12,000 BTU. That size can comfortably cool a room that is slightly over 500 sq ft. If you have sliding windows and are looking for an AC for a larger space than that, we recommend that you consider a central air conditioning system.

However, a few other aspects apart from a the room size matter when you are measuring BTUs. The height of the ceiling, the use (like a kitchen that is heated up all the time), the floor plan of the house, and the direction of sunlight are some factors that may require you to reconsider the size of the AC unit you buy.

Review of the Best AC Units for Sliding Windows

Here are some brands that have really done their job well and have been positively received. We have reviewed them for you, touching upon different aspects like BTU rating, remote control features, fan speeds and more.

PROS

  • Quiet
  • Lightweight
  • Easy to Install
  • Rapidly Cools Areas
  • Smaller Size Makes for Easier Storage

CONS

  • Not Great for Cooling Larger Spaces

Our Review

The Frigidaire FFRA0511R1 5,000 BTU 115V Window-Mounted Mini-Compact Air Conditioner is an awesome window unit that will fit into a smaller space than many other AC units. Its size makes it convenient for a number of reasons – besides easier installation and manipulation, it is also much simpler to remove and easier to stow away in a storage area during the winter months, meaning your house will be better insulated.

While you may be balking at the thought of always installing and reinstalling your AC unit, users of the Frigidaire Mini-Compact report that the whole process will take you fewer than twenty minutes. It will not take up a lot of space wherever you end up storing it, again, because of its smaller size.

And another bonus – its compactness will ensure you do not need to use an outside supporting bracket to mount it to your window. But don’t think just because it is tinier means it does not function as well as other units – with two fan speeds, two cooling speeds, and two-way airflow, there is not much this unit will not be able to do.

Bottom Line

The Frigidaire FFRA0511R1 5,000 BTU 115V Window-Mounted Mini-Compact Air Conditioner is a great sliding window unit. Its smaller size sometimes makes it struggle to cool larger areas, though.   

PROS

  • Quiet
  • Easy to Use
  • Strong Cooling Capacity
  • Can Cool Spaces Quickly
  • Good for Smaller Rooms

CONS

  • Instructions Are Not Super Helpful

Our Review

The LG Energy Star Window Air Conditioner is a fantastic sliding air conditioner that will make your life a thousand times easier with its WiFi control option. Once you download the LG SmartThinQ app on your smartphone (compatible with both iPhones and Android models), you will be able to use WiFi to adjust your air conditioner’s fan speed, temperature, and mode, as well as have the option to schedule an automatic shut down or start-up at a future time. 

If you are more old-school and are interested in the unit’s manual features, there are a number of those as well. The indoor vent points upward and circulates the cool air throughout the room, instead of just blowing it straight out the way a front facing vent would do, and the outdoor vent can be closed in order to block any stinky outdoor smells if you happen to live on a city street. Best of all, the Energy Star economy mode will still work even on extremely hot days when electric companies will lower the amount of available power.

Bottom Line

The LG Energy Star Window Air Conditioner is a great unit with some incredibly convenient aspects. It may take a little longer to set up, however, because the instructions are not very specific.

PROS

  • Quiet
  • Easy to Install
  • Will Not Increase Your Electric Bill
  • Cools More Effectively Than You Would Think Based on its Size
  • Option to Upgrade to Energy Star, Which Comes With Additional Insulation

CONS

  • Drains Poorly
  • Vents Are Not Easily Adjusted

Our Review

​​The Keystone 5,000 BTU 115V Window-Mounted Air Conditioner is an excellent product that will effectively cool any room, even those that are not the standard square or rectangular shapes.

Hands down, the coolest thing about this unit is the remote control, which comes with a temperature sensing “follow me” option. This feature essentially allows the unit to read the temperature wherever the remote is and adjust the temperature accordingly, as opposed to most units, which can only read the temperature where the unit is actually placed. With this option, you can carry the remote around with you and the unit will adjust the temperature for wherever you actually are!

It also comes with a number of other convenient features, including the ability to shut off the lighting on the unit’s face so it will not glow obnoxiously at night.

Bottom Line

The Keystone 5,000 BTU 115V Window-Mounted Air Conditioner is an effective air conditioner that will cool where you are, not where it is. It does have a complicated drainage system, though.

PROS

  • Quiet
  • Good for Smaller Areas
  • Durable, Will Last a Long Time
  • Good at Dehumidifying a Room
  • Easy to Remove and Clean Filter

CONS

  • Doesn’t Have a Timer to Program an Automatic Shutoff

Our Review

The hOmeLabs 5000 BTU Window-Mounted Air Conditioner is a fantastic unit that will get the job done for the room that it is installed in. Disclaimer – this unit is too small to cool off a large apartment or a whole house, but it will certainly effectively cool spaces such as master bedrooms or children’s bedrooms. 

The interface does not light up, meaning you will not have to worry about obnoxious glowing lights at night. This unit comes with four different settings, two fan settings and two cooling settings. It will be able to cool a room even when on the lowest setting – we guarantee you will be impressed.

And you will be even more impressed when it comes to the (non)impact this unit will have on your electrical bill. Users report that even when they are running the unit continuously, their bill only increased by about $20. A small price to pay for comfort in the heat of the summer!

Finally, this unit is also incredibly easy to use. Installation, filter changing, and everything else about this air conditioner are simple and easy to figure out.

Bottom Line

The hOmeLabs 5000 BTU Window-Mounted Air Conditioner is a great product for cooling one room within your larger apartment or home. Due to its size, it will likely not be able to cool much beyond that.  

PROS

  • Durable
  • Quickly Cools Rooms
  • Energy Efficient, Will Keep Electric Bill Low
  • Mechanical Controls Are Simple to Operate
  • Easy to Install (Users Report it Takes Less Than Ten Minutes!)

CONS

  • Heavy
  • Does Not Have a Thermostat

Our Review

The Frigidaire 5,000 BTU 115V Window-Mounted Mini-Compact Air Conditioner w/ Mechanical Controls is an excellent air conditioner unit that keeps it old school with its use of mechanical controls. If you do not want to pay extra money for a remote control or a WiFi system that you will likely never actually use, this air conditioner is the one for you. 

Its mechanical control system has two cooling speeds and two fan speeds. It also comes with vents which can be adjusted to send cool air in any direction, so you do not have to worry about this unit only being able to cool what is directly in front of it. It is a hardy little air conditioner that will last you quite a long time.

Another bonus of mechanical controls – not only is this bad boy simple to operate, but it is also quite easy to set up. Users report it will take you less than ten minutes to have it up and running! There is not much to dislike about the Frigidaire 5,000 BTU 115V Window-Mounted Mini-Compact Air Conditioner w/ Mechanical Controls.  

Bottom Line

The Frigidaire 5,000 BTU 115V Window-Mounted Mini-Compact Air Conditioner w/ Mechanical Controls is a great air conditioner that is straightforward and easy to operate. Keep in mind that it does not have a thermostat for reading the actual temperature of a room, though.        

PROS

  • Quiet
  • Easy to Install
  • Made of High-Quality Material
  • Able to Be Controlled Remotely
  • On the Lowest Setting, Still Produces a Large Amount of Cool Air

CONS

  • Its Lowest Setting is 62 Degrees, Which Some Users May Still Consider to Be Quite Warm

Our Review

The Koldfront WAC12002WCO 12,000 BTU 115V Window Air Conditioner is the leader in energy efficient sliding window AC units. Despite its high BTUs, it still only uses 1000 watts. For those not versed in electricity lingo, that means that even if you kept this unit running 24/7 for a full 30-day cycle, your energy bill would still increase by less than $100. That means this unit is actually less expensive than a central air system, which is pretty much unheard of! 

And do not think for a second that this efficiency comes with a compromise on effectiveness – this unit will still be able to cool a room within thirty minutes, and also eventually cool off an entire house. All this with 12,000 BTUs, also known as the highest BTUs a so-called “normal” outlet can process. So if you are not down with installing new 230V outlets, this air conditioner will save you that hassle. The unit also serves as an excellent dehumidifier, capable of removing several pints of water per hour from a room’s air. If you live in Florida, this may be the air conditioner for you!

Bottom Line

The Koldfront WAC12002WCO 12,000 BTU 115V Window Air Conditioner is just about the most energy efficient air conditioner out there. It might not be as cool as some of the other models, though. 

PROS

  • The kit provides a good range of window sizes it will fit in
  • If you have a narrow room, this unit can outperform its BTU rating.

CONS

  • You may have to drill an additional hole at the bottom for better draining of water and to avoid the fan splattering water.

Our Review

Frigidaire offers a range of casement units. This one is a 10,000 BTU. That can cool a room about 450 square feet.

This unit can pull up to 3.4 pints of water out of the air per hour. It plugs into a standard 115 V electrical outlet.

Other features include multi-speed electronic controls with 24-hr. on/off timer and a full-function remote control. It has auto cool, energy saver,  and sleep modes. It also offers 4-way air direction and a washable mesh filter with a “check filter” alert.

It fits sliding windows with a minimum height of 21.5 inches up to 40 inches. The window must be at least 15.5 inches wide.

Bottom Line

Frigidaire provides a limited 2-year warranty and a 3-5 year warranty on a sealed system.

PROS

  • Not very noisy.
  • This is highly power efficient unit. It consumes less energy than other ACs in the same category.

CONS

  • A few people have complained of a “plasticy” smell coming from the unit.

Our Review

Another casement AC from Frigidaire, this unit is meant for smaller rooms, around 150 square feet. It has a 2-way air directional control. Its antibacterial mesh filter has side slide out access, making it easier to clean or replace. The controls are old-fashioned rotary dials.

Bottom Line

The panels that accompany this unit fit windows measuring 23-26 inches.

PROS

  • It comes with the support bracket, making installation smooth.
  • In general, the cooling capacity is more than promised by the manufacturer. It may be able to handle a space slightly bigger than cited, but of course it depends on room use.

CONS

  • It can get a little noisy at times.

Our Review

Global Industries produces this decent 10,000 BTU AC unit - that will meet you needs for a room around 450 square feet. This AC runs on 115V.

A 4-way air directional fan helps even cool the whole room. It comes with a washable filter, so you won’t have to worry about replacements until you’ve really worn that one out.

This device can be operated by remote control. Other features include auto restart, sleep mode, and a 24hr on/off timer.

Bottom Line

Global Industrial offers a 1 year parts & labor warranty and a 5-year sealed system warranty.

PROS

  • This is one of the lower-priced slider window AC but still provides great performance and cooling ability.

CONS

  • We haven’t come across negative reports or had any bad experiences with this unit.

Our Review

Kool King offers this 10,000 BTU casement AC unit. Again, this runs on your standard home electric wiring; no need for a 220 volt installation.

It comes with electronic controls with full-featured remote and has a LED readout.

Bottom Line

Like most other units, it has four-way adjustable air direction. It also has expandable panels for flexible installation.

It weighs about 86 pounds and measures 14.6 x 23.5 x 20.9 inches.

PROS

  • Easy installation.

CONS

  • Mounting kit could be a disappointment.

Our Review

This Arctic King casement AC unit is an Energy Star-rated 8000 BTU machine.

It runs on the standard 115V outlet, and even works pretty well with a 15 amp circuit.

It has 3 Fan Speeds speeds.  There’s a sleep mode and timer. It’s energy efficiency rating is 10.9, which is acceptable.

Bottom Line

It includes a remote control and washable air filters

​Adding Security

You’ll be happy that you’ve found an efficient cooling option to cool your room with a sliding window. However, you might still be concerned about security, since it is easy to pry open the window or break it.

To help prevent anyone from sliding the window open further and popping out the AC unit, you can cut a piece of wooden dowel (like a broom handle) to block your window. Just wedge it on the opposite side between the window jamb and the frame.

Some windows also offer locks for different positions. Or you could look for special casement windows lock units at your local hardware store.

Securing the top mounting rail into the window sash with its screws is another security measure and provides your unit with more stability.

The accordion panel on the AC might also be a weakness. Be sure it’s fastened in place. A more extreme measure would be to have a grill made to go over the section.

The next step would be to install a stick-on type window alarm. While being a good way to know when you’re facing a burglar, their visibility can also be a great deterrant.

Life Hacks

Purchasing a casement air conditioner could be an expensive proposition, especially if you moved into a new house or apartment thinking your old window AC unit would work.

There are many hacks you can use to make a traditional unit work. There are many online resources that provide detailed instruction manuals and guides that will help you fit a traditional, horizontal AC in a sliding window. But it’s often necessary to get a carpenter to create the right sized frame for your window. Of course, you may need an electrician as well, but that could be the case anyway, depending on where your outlets are located and whether your unit is 120 or 220 volt.

We don’t find this a preferred method. It’s possible and if done by a competent installer, it is safe. But it can void your warranty because the unit is supposed to have a definite “top”. And if not done correctly, it can be hazardous because of electrical problems, poor ventilation or poor drainage. If you’re willing to take the risks, you can find various guides through Google, however please use caution.

Conclusion

Casement air conditioners are designed for the very specific needs of sliding windows. These units are designed to address special challenges of the window size and shape, so we definitely recommend using this type of unit where needed. It will serve you well and faithfully!

Ease of installation can vary, but many models are DIY. But you can always consult a carpenter or electrician for help where needed. There’s no reason to suffer in the heat just because of your window type - casement AC units are both good to look at and highly functional!

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