5 Best Sliding Window or Casement Window Air Conditioners 2020

If you are looking to install an air conditioning unit onto a sliding window, then you are going to need an AC unit designed especially for this purpose. 

Sliding Window Air Conditioner Units are also names casement AC units. In contrast to the typical window or portable air conditioners, sliding window air conditioners have a unique vertical design, so they can fit neatly into the available space.

All good sliding window air conditioning units arrive as a kit that includes the sliding window air conditioner itself, bars to stabilize and mount the unit in position, as well as inserts to cover the gap above the unit and provide insulation.

This makes the installation process as straightforward as possible and means you can avoid buying additional materials.

Quick Picks: Sliding Window Air Conditioner Reviews

Frigidaire Slider Window Air Conditioner
  • 10,000BTUs
  • EER Value –10.4
  • Cooling Capacity – 150
Check on Amazon
Perfect Aire Window Air Conditioner
  • 10,000BTUs
  • EER Value –10.4
  • Cooling Capacity – 100
Check on Amazon
Frigidaire Mini Window Air Conditioner
  • 5,000BTUs
  • EER Value – 9.5
  • Cooling Capacity – 100
Check on Amazon

This particular sliding window air conditioner unit by Frigidaire has a good reputation among users and is essentially a complete kit that includes everything you will need to complete the installation from start to finish.

The kit includes step-by-step instructions, the unit and inserts to fill and insulate the remaining gap.

It utilises a standard 115 V electrical outlet and includes a user-friendly digital interface and remote control for added convenience. 

This unit in particular has a BTU rating of 8,000 making it more than capable of cooling a room of up to 350 square feet.

The sleek design will blend into any room well and the louvres can be directed in the desired direction. After insulation into the window there will be a gap above, which can be covered using the plastic insert. Many people like the idea of fitting a transparent Plexiglas pane, hoowever, the double sanwhich design of the insert will provide much better insulation. 

The sliding window air conditioner unit by Global Industrial is ideal for larger spaces and can provide adequate cooling for a space of up to 450 square feet. 

Like the Frigidgaire this unit does include an insert to ensure the space above the AC unit is covered and well insulated. 

The interior contains 4 powerful fans that do a superb job of keeping the room cool and comfortable.

A great advantage of this unit is that the filter inside is machine washable so you will save a considerable amount compared to units that require a regular filter replacement. 

The Global Industry AC unit also comes with a remote control allowing you to control the settings from the comfort of your seat. Settings include auto-start, sleep mode and a 24 hour on/off timer. 

The Frigidaire has a good reputation for providing great cooling performance for those with a limited budget.

There are a few key reasons for their cooling efficiency, firstly is the eco-friendly R410A refrigerant, that provides swift and powerful cooling for a modest 150 square feet, which is a significant advantage over other units in the same price range.

Additionally, the design features 2-way directional louvers which allow you to control the direction of the air flow either left or right by adjusting the auger wheel located in the center.

This makes for a combo that has received feedback for helping to reduce the temperature of small to medium sized spaces quickly and efficiently. 

The filters are designed to be antibacterial, which may impress the germophobes out there. The kit does come with panels to cover up the side spaces, but bear in mind there is a lower limit of 23 inches. 

The Frigidaire air conditioner is a compact unit designed to provide adequate cooling for smaller rooms where you don’t want the unsightly presence of a large and bulk AC in your window. In terms of exact dimensions, the unit has height of 12″, width of 16″ with a depth of 13 3/4″.

Although this unit lacks the convenience and controls of a digital interface, the simple and manual knobs remain favored by many users. This portable air conditioner unit is equipped with two mechanical style knobs clearly numbered and labelled allowing the mode and temperature settings to be altered with ease.

Frigidaire kept it simple with this unit by only including a set of basic modes. This includes a knob allowing the room temperature to be controlled with a range of 1-7, as well as a knob allowing you to alter the mode between fan or cool mode. The fan mode can be set to high or low and operates the AC unit by simply circulating the air without switching on the compressor.

This window air conditioner by Perfect Aire boats a 10,000 BTU rating, making it great for medium to large sized spaces (up to 450 square feet to be precise).

Like the other models we have listed, this one too comes as a kit and includes the unit and inserts to take care of the gaps, as well as window mounting materials. 

Unlike many other AC units that require professional wiring, this one can be simply plugged into the home power outlet and turned on for instant operation. 

While the LG LW1216ER is a pricier option, overall it certainly has a good reputation.

In our view is probably the best small AC suited for those wanting to cool larger rooms and spaces (up to 550 square foot).

The G LW1216ER is pretty much what you would expect from any modern AC unit, it’s a small model designed to fit on most sized windows.

In comparison to cheaper models, it’s build is sturdier and the quality of the construction is clear, with a nice looking digital interface and sleek looking louvers that aren’t flimsy or easily scuffed and broken, which can be common in cheaper alternatives.

The digital interface on the LW1216ER is incredibly easy to use and comes equipped with a handy remote control for operation from the comfort of your armchair.

The interface includes temperature control, fan speed, a timer, as well as an energy saver mode for those who want to reduce their carbon footprint and save a little money.

This unit also includes a remote control for maximum convenience. The digital controls on the unit are also very easy to use. Settings include energy saver, sleep mode and several fan speeds that allow you to make adjustments as your cooling demands change throughout the day. 

What Air Conditioning Will You Need for a Sliding Window?

The obvious obstacle with a sliding window is the frame, which makes installing a traditional window air conditioner practically impossible. For this reason, a casement style AC unit is essential so that you can be confident it will fit into the available space. With this in mind, you will need to measure the dimensions prior to buying a unit to make sure it will fit the window you have in mind.

Sliding window AC units come in a variety of sizes so finding one for your home shouldn’t be an issue. They usually start their sizes at 20 inches and go from there, which is ideal for small to medium sized rooms.

Check the British Thermal Units (BTUs)

Another thing you will want to consider is the BTU rating of the air conditioner. This stands for British Thermal Units and is a metric used to show the cooling potential of the unit i.e. the amount of heat it can remove from a space per hour (BTU/hr).

Depending upon your room size, you will need to calculate the size you will need of the appropriate system. The following is an example given for a standard room with 8-foot ceilings (roughly 20 BTU for each square foot):

  • 8,000 BTUs will cover 200 sq. ft. (1,600 cubic feet)
  • 10,000 BTUs will cover 300 sq. ft. (2,400 cubic feet)
  • 12,000 BTUs will cover 400 sq. ft. (3,200 cubic feet)
  • 13,000 BTUs will cover 450 sq. ft. (3,600 cubic feet)
  • 14,000 BTUs will cover 500 sq. ft. (4,000 cubic feet)

Not only is it important to select an AC with the right BTU to ensure maximum comfort, but if you select a unit that is the wrong size it can cause other issues too. For instance, if you use an AC unit that is too small then it won’t be able to adequately cool the room, while a unit that is too large will frequently turn on and off leading too component strain and inefficient energy use.

Make sure to read the back of the box as brands usually provide helpful instructions on selecting the right sized unit for your unique circumstances. Not only does it depend on room size, but also climate, shading and window type and size.

How to Install a Sliding Window Air Conditioner

Most people worry about installing a new sliding window air conditioner, especially if you intend on it being a new DIY project and you have little experience.

In reality, it’s a relatively straightforward process and the majority of units today provide pretty good step by step instructions. But In any case, you can always hire a local HVAC installation technician to help you if you are struggling. 

Here are the general steps to install a new window AC unit:  

1. Measure your window space – Before you choose a a new unit, you’ll need to measure your window to ensure you have the correct dimensions at hand when you order. Slide your window open and measure all dimensions in inches. 

2. Position your AC unit – You will probably need some helping hands for this step as it involves positioning your air conditioner onto the window frame. This is generally after positioning the brackets on the base and the frame that will run horizontally. 

3. Fit the Inserts – Once you have the AC in place it’s time to fit your inserts, which is typically either a plastic sandwich made from styrofoam or plexiglass. 


If you have a sliding window, then a sliding window air conditioner unit offers the perfect (and obvious) solution. Installation kits, such as the ones offered by Frigidaire provide everything you need for a straightforward installation process, so these are the best choice for those wanting a hassle free set-up. 

You can easily install these yourself and they are made with that intention. However, if you are facing difficulties don’t be afraid to consult a local HVAC specialist. 

About the Author

Dave Miller is a HVAC technician with over 10 years in the industry. Dave created HeatTalk with the ambition for it to become a resource for individuals looking for answers, whether they be a layman, student or a professional.