Best Casement/Sliding Window AC Units – 2020 Buyer’s Guide

| Last Updated: November 14, 2020

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-conditioners.

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.

Our Top Picks for Sliding Window Air Conditioners

  • 10.8 Energy SEER level
  • 8000 BTU
  • Cools 350 sq. ft
View Latest Price →
  • Temp between 62 - 86°F
  • For various windows
  • Complete coverage
View Latest Price →
  • Remote control
  • Auto-restart settings save
  • Most budget-friendly
View Latest Price →

Comparison of the Best Sliding Window AC 

  • Has an energy SEER level of 10.8
  • BTU of this air conditioner is around 8000
  • Can cool a room that is approximately 350 sq. feet
View Latest Price →Read Customer Reviews
  • Temperature can be set between 62°F - 86°F
  • Window mount kit is expandable to accommodate various windows
  • Remote control has portable thermostat tech for complete coverage
View Latest Price →Read Customer Reviews
  • The Unit Can Be Controlled Via Remote Control
  • The Auto-Restart Will Save Your Settings
  • We Believe This is the Most Budget-Friendly A/C on the Market
View Latest Price →Read Customer Reviews
  • Has a high energy efficiency rating
  • The multiple airways will cool the room evenly
  • This AC unit can be controlled from your smartphone
View Latest Price →Read Customer Reviews
  • Dehumidifies 3.4 Pints Per Hour
  • EER 10.4
  • Designed for both sliding and casement windows
View Latest Price →Read Customer Reviews
  • Covers around 450 sq ft
  • Full installation kit
  • Four-way air direction control
View Latest Price →Read Customer Reviews

Aspects to Consider When Buying a Vertical Sliding Window/Casement 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:


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 home 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 a remote control, Wi-Fi, or temperature sensing ability.

Because these units are installed in windows, you will not have to worry about rigging up some complicated new electrical and hose systems the way you would need to do with a standing indoor AC unit – the water for these systems can just drain right out of the window itself!


Vertical window air conditioners are not exactly the most attractive element of a home décor system. It is pretty hard to sugarcoat how bulky 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. 

Frigidaire FFRS1022R1

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 horizontal sliding window model and incorporating more vertical sliding window systems.

Think about it: an air conditioning unit that is installed in a vertical sliding window has much more support on either side to hold it in place. An air conditioner installed in a horizontal 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.

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 vertical sliding window and a horizontal 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 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 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 the room size matter when you are measuring BTUs. The height of the ceiling, the use, 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.

Quick Take: Best Sliding Window AC Units

These are our recommendations for the best sliding window AC units:

  1. Frigidaire FFRS0822S1
  2. PerfectAire 3PASC10000
  3. Keystone 5,000 BTU 115V Window-Mounted Air Conditioner

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.


  • Comes with double-wall thickness for more durability
  • Higher relative warranty makes the model more reliable
  • Noise levels are significantly lower than most other models
  • Remote control allows you to better control a range of settings


  • Installation is time-consuming
  • Weight is relatively more than most other models

What Recent Buyers Report

Recent buyers have only positive things to say about this product. They feel that this model brings them all the features without being very expensive. This includes a perfect remote control that gives them more control over the temperature settings. They have also praised the diverse settings that appear on the conditioner that gives them more control over the temperature they want inside of the room.

Why it Stands Out to Us

Among many other things, this air conditioner stands out to us because of its amazing dehumidification tendency. Rooms can get really stuffy, and bad smells can develop after a couple days of traveling. This, coupled with humidity, can give rise to algae and moss and can make the inside of the room unbreathable.

To help reduce the humidity effects, this portable air conditioner has the ability to remove more than 3 pints of water from the air each hour.

Who Will Use This Most

This model comes with a relatively lower BTU, but this is compensated by a good SEER level. This air conditioner isn’t very big, either, which makes it easy to install. Moreover, it also reduces the energy consumption of the model and makes it economical in the long run. The power it requires to run is 115V. Moreover, the model has the ability to cool rooms up to 350 sq. feet.

Bottom Line

With a perfect energy Seer and better humidification factor, this model is already making rounds in the industry and is considered as one of the most reliable ones. This is also assured by the company providing a better overall warranty. This, coupled with the high-end construction of the model, increases the faith of buyers towards the model.

PerfectAire 10,000 BTU Slider Air Conditioner Window A/C - Casement, 10000, Gray


  • Tilt-out air filter allows easy cleaning
  • Offers three speeds in fan and cool modes
  • Adjustable temperature settings with a range of 62°F to 86°F
  • Portable thermostat technology ensures total room coverage
  • Effectively cools areas measuring between 400 and 450 square feet


  • Operation is a bit noisy
  • Does not include a heat mode

What Recent Buyers Report

The majority of buyers were extremely satisfied with their purchase and particularly loved the functional remote that doubled as a thermostat. Although some users found the unit’s operation to be a bit noisy, most stated that it was easy to install and cooled well.

Why it Stands Out to Us

Boasting four different operating modes, this unit enables users to fully customize their climate. It offers dehumidification, auto, a cooling mode, and a fan mode, and gauges the natural climate changes to determine the operating mode that will best suit your needs. It further features a washable and removable air filter that ensures healthy and clean air.

Who Will Use This Most

This 10,000 BTU unit can cover areas of up to 450 square feet. It’s also programmable, so you can set it to switch off and on by itself. This makes it perfect for those who want to conserve energy or want the house cool before they return. However, its operation is a bit noisy so it may not be suitable for the bedroom if you’re a light sleeper.

Bottom Line

Cooling rooms measuring up to 450 square feet, this PerfectAire model easily fits in architectural windows, eliminating the need for costly custom designs. With three fan speeds, full-range direction control, and adjustable temperature settings, it allows you to easily find your comfort zone.


  • 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


  • Drains poorly
  • Vents are not easily adjusted
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, that 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.


  • Quiet
  • Easy to use
  • Strong cooling capacity
  • Can cool spaces quickly
  • Good for smaller rooms


  • Instructions are not super helpful
The LG Energy Star Window Air Conditioner is a fantastic sliding air conditioner that will make your life a thousand times easier with its Wi-Fi 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 Wi-Fi 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 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.


  • 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


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

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

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.


  • Comes with a 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


  • Can get a little noisy at times

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

A 4-way air directional fan helps cool the whole room evenly. 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.

Best Casement Window Air Conditioner:
 hOmeLabs 5000 BTU Window Mounted Air Conditioner


  • Quiet
  • Good for smaller areas
  • Durable, will last a long time
  • Good at dehumidifying a room
  • Easy to remove and clean filter


  • Doesn’t have a timer to program an automatic shutoff
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 a large apartment or a whole house, but it will certainly 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 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.  


  • Has a 16 ft. range for better customization
  • Remote control that adds to greater comfort
  • Features different speed levels and a sleep mode
  • Comes with all installation hardware that you will need
  • Energy efficiency that is relatively higher than most models


  • Lower BTU than some other models
  • Repair and replacement of parts are often costly

What Recent Buyers Report

Most recent buyers are thrilled to have finally gotten their hands on a superior model that is cost-efficient in the short and long run both. It is extremely compact, making it easily portable. This also makes its installation in a range of windows easy. Not only this, but buyers are also pleased with the high SEER of the model, which makes the model have a good overall impact.

Why it Stands Out to Us

The model’s control panel is its novelty and offers users the most comfort. It comes with a very easy to see and operate digital display. Unlike other models, this isn’t very small and is visible from afar too.

Moreover, it comes with different fan speeds that control the airflow inside the room. People residing inside the room or RVs can easily change the fan speeds according to their mood. The dehumidification ability is also noteworthy.

Who Will Use This Most

The model is made for people who want cost efficiency, as well as speed efficiency at the same time. It comes with 3 different fan speeds, and its remote control has a range of 16ft. This means that larger RVs can also make use of these air conditioners.

Moreover, the model is not very tall, which makes installation easy. It can cool a room that is about 350 sq. ft., making it suitable for a range of RVs and other rooms.

Bottom Line

With this portable air conditioner, keep the summer heat aside and enjoy non-stop and never-ending cool breezes at all times, even inside your RV. This compact air conditioner is one of the easiest ones to install and does not require any additional hardware for its installation. It also comes with good BTU. But the reason most people prefer it is because of its relatively lower price.


  • Quiet
  • Lightweight
  • Easy to install
  • Rapidly cools areas
  • Smaller size makes for easier storage


  • Not great for cooling larger spaces

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.   


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


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

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 an 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.


  • Easy installation


  • Mounting kit could be a disappointment

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, a sleep mode and timer, and it’s energy efficiency rating is 10.9, which is acceptable.

Bottom Line

It includes a remote control and washable air filters.


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


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

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 anti-bacterial 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.


  • 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


  • Heavy
  • Does not have a thermostat
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 Wi-Fi 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 that 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.        


  • 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


  • Its lowest setting is 62 degrees, which some users may still consider to be quite warm

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 don't 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. 


  • Can work on energy saver mode
  • Energy efficiency is high with its 10.4 SEER
  • Provides more protection against the growth of algae or moss
  • Inclusion of a dehumidifier helps free your room from any moist
  • Comes with weather seal technology that allows for an easy setup


  • Can fit casement windows only
  • Can't be installed in any space that slides up

What Recent Buyers Report

Users looking for more efficiency absolutely love getting their hands on this portable air conditioner. This not only provides them with better regulation, but its amazing dehumidification technology ensures that the inside of your room is always ventilated and free from any foul smell. Not only this, but it also decreases the growth of tiny microorganisms inside.

Why it Stands Out to Us

The Koldfront BTU is the most noteworthy feature of the model, and everyone will agree that having higher BTU makes your air conditioner more powerful. It can gradually decrease the temperature inside of your room by removing more amount of heat per minute. Not only this, but it also decreases energy wastage and provides you with a good overall yield.

Who Will Use This Most

The model comes with all installation software that you will need for its proper placement. It also comes with all the weather seals, which means that you don’t have to hire a professional to install it. It also has a relatively higher BTU and energy SEER, which makes it suitable for larger rooms. So if you live inside a tiny cabin or a small RV, then it is recommended that you invest your money in a smaller air conditioner.

Bottom Line

When compared to its counterparts, this model has a relatively higher BTU, which makes it the most energy-efficient model in this review. It also has the ability to cool extremely large rooms, ranging from 400 to 450 sq. ft. Although this makes the model slightly expensive, the plethora of features that it promises the users makes it worth a few extra bucks.

Best Casement Window Seal
  HOOMEE 400


  • Prevents entry of any additional hot air from all sides
  • Installation is made easy with the help of a thorough guide
  • Has the ability to lock the hose between your window frames
  • Does not require you to buy any additional tools for installation
  • Suitable for a range of rooms and people because of better controls


  • Requires cleaning more frequently than others

What Recent Buyers Report

There are many reasons why this seal is considered one of the best, the top being its ability to help regulate fuel consumption. There are 2 reasons why this is appreciated by recent buyers. They praise it for being a cost-effective model that lowers the electricity bills in the long run.

Moreover, with global warming on the rise, it helps recent buyers protect the planet by lowering their carbon footprint.

Why it Stands Out to Us

The main purpose of a portable air conditioner is to increase the cooling in your room, and ensures a properly balanced distribution of cold air in all corners of your room by not allowing air to escape through gaps in the window. 

It also zips around the nozzle of the hose and blocks any kind of warm air from returning. This, coupled with better efficiency, helps ensure that people sitting in all corners feel an equal amount of cold.

Who Will Use This Most

Unlike other models, this one doesn’t come with a restriction of size. It can fit around any casement air conditioner. It is also suitable for most of the windows in your home that open from left to right. It can fit in windows with a maximum distance of 400 cm between the panels.

Bottom Line

With so many amazing features at its disposal, it’s no wonder it had to be included on our list. It comes with high-end construction that offers better durability and strength. It also offers easier installation and does not require a professional to do it. If you are looking to increase the efficiency of your air conditioner, this window seal will fit the bill perfectly. 

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 window 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 deterrent.

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.

How to Install Portable Air Conditioner in a Horizontal Sliding Window

You may have gotten the best portable air conditioner on the market, but unless you learn to install it inside your sliding window, you won’t be able to enjoy its benefits. To help you make things easier, here is our step by step guide for AC installation. Make sure you watch the video link given below to have a better understanding of these steps.

  1. The first step is to measure your AC from the left side to the right side, including the frame of the AC.

  2. Then cut the pieces of your C channel in half. In the first section, insert the nut rod by coupling it on one end.

  3. You need to then drill a hole on the side of the frame. This will be done through the channel and by coupling it with a screw.

  4. You need to make sure it’s flushed on each end.

  5. Then you need to measure your windows from top to bottom. You need to make sure this includes the inside of the frame too.

  6. This is important because you need to fit the AC channel into the frame.

  7. You need to then place your AC inside of your frame and slide it carefully to the side frame as far as you can. If the frame inside of your AC is well attached, you should not worry about any issue, such as, the unit falling out.

  8. You need to then insert the vertical C channel and drill a hole right above the horizontal channel. Then you need to screw the two together to ensure they are properly attached.

  9. You need to then screw your C channel into place by using self-drilling screws. You will also have to drill through the window frame in order to do this.

If these steps are too difficult to understand, you can have a look at the following video to get a better understanding.


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!

People Also Ask

Coming across multiple reviews on the internet, we noticed how people are still confused about the sizes of the models. They also ask numerous questions regarding the installation and the size that fits the window. So to help all these people out, we decided to answer some of the most popular questions by you.

Can You Put an Air Conditioner in a Sliding Window?

Most of the window air conditioners are meant to fit inside a vertically sliding window only. This means that larger and horizontal sliding windows in your house will be left out. So, before you invest in a room conditioner, make sure you check the BTU setting and buy only the most appropriate size.

Can You Put an AC Sideways in a Window?

This is one of the most popular questions asked. If you have a window that can slide open from left to right side and a regular-sized window air conditioner, then it is best you don’t install the appliance in the window by turning it towards one particular side. Doing this might result in the burning of your compressor and hence disrupting the unit that’s inside.

My name is Bob Wells and I am a retired HVAC tech from Washington state. I am currently retired and no longer do much with HVAC, however, I feel like I have a lot of knowledge in the subject and I wanted to create a website where I could talk about what I've learned and help upcoming HVAC techs. Find more info about me and HVAC Training 101.