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Through-The-Wall Air Conditioner Buying Guide

Thru-Wall AC Buying Guide

Through-the-wall air conditioners are self-contained units that quickly cool rooms and other spaces. They're similar to window ACs but are installed through an exterior wall and use a wall sleeve for support. Installing a thru-wall AC in your living room, bedroom, or office is an efficient way to keep you cool and comfortable all year. Most new models do more than just cool; they're packed with multiple modes and energy efficient, convenient features.

For easy access to the topics in our buying guide, click the titles below:

Window ACs vs. Through-the-Wall ACs

It's easy to compare window and thru-wall ACs, because they're similar in cooling capacity and size, but through-the-wall units tend to be slightly more efficient because they create an airtight seal in the room.

The major differences between these ACs involve installation and venting. Window ACs fit through a window and don’t require permanent installation, while thru-wall ACs are actually built into the wall—making them popular in rooms without windows or for people who prefer to leave their windows alone.

Wall air conditioners typically only vent warm air through the back of the unit, while window ACs vent from the sides and back. For this reason, window and thru-wall models are not interchangeable (even if they're the same size). In most cases, if a window unit vents out its side, the wall will block the vents and cause overheating. Select window AC models can be installed through a wall, but only if they have a slide-out chassis wall sleeve. Read more on wall sleeves.

Room Size

As with all room ACs, purchasing a model with the appropriate cooling power is the most important place to start. Through-the-wall ACs use British Thermal Units (BTUs) to measure their cooling capacity: The higher the number of BTUs, the more square footage the AC can cool.

Use the chart below to find the ideal cooling capacity for your room size:

Area To Be Cooled
(Square Feet)

Capacity Needed
(BTUs Per Hour)

100 to 150 square feet

    5,000 BTUs

150 to 250 square feet

    6,000 BTUs

250 to 300 square feet

    7,000 BTUs

300 to 350 square feet

    8,000 BTUs

350 to 400 square feet

    9,000 BTUs

400 to 450 square feet

    10,000 BTUs

450 to 550 square feet

    12,000 BTUs

550 to 700 square feet

    14,000 BTUs

700 to 1,000 square feet

    18,000 BTUs

1,000 to 1,200 square feet

    21,000 BTUs

1,200 to 1,400 square feet

    23,000 BTUs

Determine the model you need based on the square footage and environmental conditions of your room. Environmental conditions to consider include:

  • Natural Sunlight: If your room gets a large amount of sunlight, consider purchasing an AC with approximately 10% more BTUs. Reduce the number of BTUs by 10% if your room gets very little sunlight.
  • Ceiling Height: These estimations are based on rooms with 8-foot ceilings. You'll want to increase your BTU level slightly if your ceilings are higher than 8 feet.
  • Number of Occupants: If more than 2 people occupy your room or space regularly, you should add an additional 600 BTUs of cooling power for each person.

Installation: Wall & Electrical Requirements

Installing a thru-wall air conditioner is permanent, but it's not as hard as you may think. Follow the manufacturer's instructions carefully, particularly when it comes to the hole size. Your model needs to be installed properly for safety and efficiency reasons. The main things to consider before installing your model are the wall you use and the electrical requirements:

Wall Requirements: Ensuring you use an appropriate wall is the most important part of installation. Make sure you check for any plumbing or electrical structures inside the wall before you cut the hole. Consider consulting a professional for first time installation because the hole needs to be measured and cut precisely.

All thru-wall ACs must be vented, so they need to be installed in an exterior wall. Other wall considerations may need to be taken into account (like wall thickness), so double check the unit and sleeve dimensions before you start. Read your owner's manual for any additional requirements.

Electrical Requirements: Make sure the voltage requirements for the AC work in your home. Most new thru-wall ACs use standard 110-120-volt plugs, but some larger or older units use 220 volts. For models with voltage requirements that don’t match yours, you may need to install special electrical wiring or consult an electrician. The power cord needs to be long enough to reach an outlet once it's installed; most manufacturers don't suggest altering or extending the cord.

If you're replacing an existing unit, purchase an air conditioner with the same electrical requirements.

Replacing Thru-Wall Air Conditioners

Replacing a thru-wall AC is fairly simple, and the main consideration is the wall sleeve. All through-the-wall air conditioners require wall sleeves for support, installation, and maintenance. Be sure to check if a wall sleeve is included with your AC; traditional through-wall sleeves generally need to be purchased separately. If you're replacing an old thru-wall AC, you can use the existing sleeve for your new model— just make sure it's compatible the existing sleeve.

An air conditioner can either have a slide-out chassis sleeve or a traditional through-the-wall sleeve. A slide out chassis is essentially a built-in sleeve that comes with the unit. Before replacing an AC, determine the type of existing sleeve. If your AC only vents in the back, then it uses a through-the-wall sleeve. To replace this model, simply buy another unit that also vents in the back and fits your sleeve . If your model has a slide-out chassis and vents out the sides and back, take slightly more precaution before replacing it. Generally slide-out chassis are compatible with specific models.

Fortunately, many brands make standard AC sizes that fit sleeves from other brands. This makes installation simple; just remove the old model and replace it with your new one. Your AC should come with information on which wall sleeves it fits. Sometimes trim or other material helps seal the area around the unit so it can fit different sleeve sizes. 

Some brands, like Friedrich, offer models that fit wall sleeves from other brands. Select thru-wall units fit sleeves from brands like Amana, GE, Whirlpool, and Frigidaire.

Select window AC models can be installed in both windows and walls. These models have slide out chassis, which makes them more versatile than traditional window units. Before installing a window unit through a wall, look at where its air vents are located. ACs that vent only in the back are great for thru-wall installation, but if they also vent out the sides, you need to make sure your wall won't block the vents. This causes efficiency issues and prohibits your model from working properly.

Energy Efficiency

Through-the-wall air conditioners are an energy efficient way to cool to your space, particularly in small- to medium-sized areas without access to central air conditioners. Each thru-wall model comes with an Energy Guide Label that's a snapshot of its energy-related information. This label shows:

  • The unit's number of BTUs (cooling power)
  • Its estimated yearly operating cost
  • The Energy Efficiency Ratio (EER) for the unit

A model's Energy Efficiency Ratio (EER) is the most common way to measure efficiency. EER looks at how many BTU's per hour are used for each watt of power the AC draws. It's determined by dividing watts by the number of BTUs (BTUs/wattage). Higher EERs mean greater energy efficiency. ACs with a 9.7 or higher are generally considered efficient models. ACs with high EERs save you money in the long run, particularly if the units are used frequently.

Thru-wall ACs that are at least 10% more efficient than comparable models can become Energy Star-qualified. The EPA and U.S. Department of Energy determine what models are labeled as Energy Star. If you purchase an Energy Star thru-wall AC, then you can be confident you've purchased an efficient model. These AC models tend to save consumers about $50 over the lifetime of the unit.

Many features and modes can help thru-wall ACs achieve the Energy Star seal:

  • Energy- or Money-Saver Modes: These operating modes use less energy while keeping your space cool. When operating in one of these modes, your AC will typically stop the cooling cycle once your set temperature is reached and then cycle on and off to maintain it (instead of continuously running in Cool mode).
  • Programmable Timers: Generally programmable up to 24 hours, timers set your AC to turn on and off at certain times. For example, you can set your AC to turn on right before you get home from work, so you walk into a cool space without running it all day. On the flip side, you can also program it to turn off when you know you won't be home—ensuring your AC only runs when needed.

In addition, maintaining your AC's air filter will increase its efficiency. Be sure to wash or replace air filters as suggested by the manufacturer.

Heat and Additional Modes

Models with additional modes can keep your space comfortable all year. The most common mode customers look for is Heat mode. Many wall ACs offer supplemental heat for winter months, and they typically use electric heat or a heat pump to provide warmth. Electric heat uses an internal coil to produce heat and a fan to disperse it around your space; a heat pump is the opposite of an air conditioner: it transfers heat from a colder area using mechanical energy. Since heat pumps move heat instead of create it, they're generally more efficient than electric heat systems. Electric heaters tend to be more reliable and are popular in areas with more dramatic climate changes.

Please note: Heat modes are not intended to heat your entire home and should be viewed as additional heat for specific rooms. Other modes thru-wall ACs offer:

  • Dehumidify mode helps the AC removes excess moisture from your home.
  • Fan-Only mode is ideal for preventing room stuffiness on days when Cool mode isn’t needed.
  • Sleep mode is a quieter operating mode that uses less energy and is a great option for when you sleep.

Look for the previously mentioned Energy Saver and Money Saver modes on higher-end thru-wall ACs.

Convenience Features

Through-the-wall ACs include various features to make using them as convenient as possible. Look out for these features when purchasing a new AC:

  • Digital Controls: Digital controls make changing your settings easy and allow you to set more accurate temperatures.
  • Adjustable Louvers: Direct your air to a specific location by adjusting its louvers. Some models even have automatic-swing louvers that automatically move cool air around your room.
  • Remote Control: Most new models come with remote controls to conveniently change the set temperature and other settings.
  • Auto Restart: This mode automatically restarts the motor in the event of a power failure or outage. Once power is restored, the air conditioner will operate in the last programmed setting—a great feature for computer/server rooms.
  • Washable Air Filters: Reusable air filters not only collect dust and other particles, but they can be washed to save you money on replacements.
  • Programmable Timer: Program your AC to turn on or off up to 24 hours in advance, which saves on energy bills and gives you more control over when it runs (only when you need it!).

Consider This

Unlike many room air conditioners, thru-wall ACs require permanent installation. If you're looking for a room air conditioner that doesn’t require permanent installation, consider a portable AC or window AC.

Still Have Questions?

For more information on specific thru-wall air conditioners and other indoor air treatment solutions, shop our products and visit our Knowledge Center. Not sure what's best for you? Contact our product experts toll free at 1-800-934-9194. We want to help you make your indoor environment healthy and comfortable.

Other Resources

How to Choose a Room Air Conditioner
Types of Room Air Conditioners


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