Difference Between Window and Through the Wall Air Conditioner

Window AC VS Wall AC

The difference between window and through the wall air conditioners are the way the units are designed, how they are installed, efficiency, costs and sizes.

Design Differences

A window AC vents out the back, of course, as does a through the wall AC. But the window unit also has vents on the side – on the back half of it that sticks outside the window.

A through the wall AC only vents out the back, since it is installed in a sleeve that surrounds all four sides, leaving zero room for side ventilation.

Installation Differences

This is obvious, of course. The design differences demand different installation locations.

A wall AC could be installed in a window, but you would have to fabricate the side panels or “wings” to fill the space between the unit and the window frame. It’s not a good idea, because air gaps would likely be a problem – pulling warm, humid air into the house as you try to get rid of heat and humidity.

And it would likely be difficult to secure the unit in the window to prevent it from falling out.

A window AC can only be installed in a window.

You should not install a window air conditioner in a wall sleeve. This is because a window AC vents both out the back and out the sides, as noted, and putting the unit in a sleeve will prevent side venting.

Efficiency Differences

Window ACs are more efficient than through-the-wall air conditioners.

However, there are many Energy Star certified models in both types.

Window AC CEER ratings range from around 9.1 to 15.7 for current Energy Star models.

Through the wall ACs top out at about 12.0 CEER.

The US Department of Energy’s Energy Star program lists 1125 current window air conditioners and 216 through the wall air conditioners that meet its criteria. Keep in mind that there are far more window ACs manufactured, so the difference in numbers aren’t surprising.

Size Differences

Window ACs are manufactured in a wider range of sizes from 6,000 BTU to more than 20,000 BTU.

Wall ACs start at around 6,300 BTU. The largest are around 15,000 BTU.


Generally speaking, through the wall air conditioners cost 2-3 times more than window units depending on which models you are comparing.

The extra cost is due to design differences, the fact that far fewer wall ACs are made and the addition of the sleeve.

Plus, cutting and framing the opening, if done by a pro, can double or triple the cost of the entire project.


Any window unit will reduce some of the view out the window. This is true even if you purchase a low profile model like those from Soleus Air that fit over the sill and down the inside and outside of the wall.

Frigidaire makes short window ACs, but they still somewhat impede the view.  


Wall air conditioners are more secure than window ACS, since window air conditioners can be easily pulled out of the window and provide an entry point for an intruder.

In terms of security, through the wall ACs are also less likely to fall out of their installed spot.

What is the Same Between a Window and Wall AC? Features – digital controls, remotes, timers, eco-mode for saving energy, Dry/Dehumidify mode, WiFi on some models – these are features common to both types of room air conditioners.

Window ACsThrough-the-Wall ACs
DesignSide and Rear VentilationRear Ventilation
InstallationWindow OnlyWall Preferred / Window Possible
Efficiency9.0 to 15.7 CEER8.8 to 12.0 CEER
Size6,000 to 24,000+ BTUs6,300 to 15,500 BTUs
Cost$200 to $1,200$450 to $1,400+
VisibilityReduces Window VisibilityNo Visual Impact
SecurityModerate or High Risk Low Risk

Installing a Window AC in a Wall

You should not install a window air conditioner in a wall sleeve.

Why? There is one major problem with installing a window air conditioner in a sleeve.

Ventilation – pure and simple. A sleeve restricts side venting from a window AC.

Window air conditioners rely on side vents to get rid of two things you don’t want in your home.

1). Heat. That’s the easy one. A window air conditioner refrigerant collects heat inside, transfers it through a heat exchanger to the outdoor coil. That’s the radiator-like part on the back of the unit that the heat dissipates through.

When a window air conditioner is installed in a wall sleeve, some of the coil fins are covered, so the heat stays in your home. The sleeve warms up, warms the framing of your house, and some of the heat inevitably re-enters your living space.

2). Humidity. This is even worse! As an AC removes heat, the indoor coil gets super cold. Moisture from the air in your home condenses on it and drains out the rear of the unit.

If the unit is in a wall sleeve, some of that moisture can leak into the sleeve frame, make its way through cracks into your home’s framing, and cause mold.

Buy a Through the Wall AC

This is the obvious solution – one you’ve already considered. And yes, wall air conditioners are a lot more expensive than some window ACs.

They cost up to 4 times more than window air conditioners, depending on what models you are considering. Plus you have the expense of cutting and framing the opening.

But the problems listed in the next section will be eliminated – No blocked view. No security issues. And no “oops it fell” danger.

Another Option – Where to Install a Window AC Other than the Window

If you “must” install a window air conditioner in a wall, consider this method:

Build a frame for it that is thinner, so it doesn’t block the airflow needed for ventilation.

A sleeve usually 12” to 16” deep. Instead, create a space in your wall that is the width of the window frame, usually 4” to 8” depending on the stud dimensions used to frame your home.

This custom sleeve should both hold the unit securely in place and allow for proper venting.

Pro Tip: Measure the width of your home’s walls – this can be done through an open window. And then measure the ventilation space on the side of the window AC.

This allows you to make sure that the venting areas are not blocked.

Written by

Rene has worked 10 years in the HVAC field and now is the Senior Comfort Specialist for PICKHVAC. He holds an HVAC associate degree and EPA & R-410A Certifications.
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