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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
Global Industrial Casement Window AC
Kool King Slider AC
Arctic King AC
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.
Quick Take: Best Casement Air Conditioner Units
These are our recommendations for the best casement air conditioner units:
Reviews 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.
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.
Frigidaire provides a limited 2-year warranty and a 3-5 year warranty on a sealed system.
- If you have a narrow room, this unit can outperform its BTU rating.
- The kit provides a good range of window sizes it will fit in
- You may have to drill an additional hole at the bottom for better draining of water and to avoid the fan splattering water.
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.
The panels that accompany this unit fit windows measuring 23-26 inches.
- This is highly power efficient unit. It consumes less energy than other ACs in the same category.
Not very noisy.
- A few people have complained of a “plasticy” smell coming from the unit.
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.
Global Industrial offers a 1 year parts & labor warranty and a 5-year sealed system warranty.
- 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.
- It comes with the support bracket, making installation smooth.
- It can get a little noisy at times.
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.
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.
- This is one of the lower-priced slider window AC but still provides great performance and cooling ability.
- We haven’t come across negative reports or had any bad experiences with this unit.
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.
It includes a remote control and washable air filters
- Easy installation.
- Mounting kit could be a disappointment.
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.
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.
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!