Sizing Up Your Options
Before you consider price and features, start by determining how powerful an air conditioner you need. The bigger the room, the more power is required, as expressed in British thermal units (Btu).
To calculate the square footage of your room, multiply the length of the room by the width.
A small bedroom or office of 100 to 250 square feet probably needs a window unit between 5,000 and 6,500 Btu. A larger bedroom or playroom that’s between 250 and 350 square feet probably requires an AC of between 7,000 to 8,500 Btu. A living room, family room, or open plan space of between 350 to 550 feet would be best served with a unit of between 9,800 and 12,500 Btu.
The window air conditioners in CR’s tests have cooling capacities ranging from 5,000 to 12,500 Btu.
But don’t buy by Btu alone. Energy Star recommends that you make allowances for other considerations—such as the height of your ceiling, where the unit will be placed, and the size of your windows and doorways. In addition:
- If the room is heavily shaded, reduce capacity by 10 percent.
- If the room is extra sunny, increase capacity by 10 percent.
- If more than two people are often in a room, add 600 Btu for each additional person.
- If the unit is used in a kitchen, increase capacity by 4,000 Btu.
Features to Consider
Energy efficiency: New Energy Star certified room air conditioners come with better insulating materials and clearer instructions to help ensure that you get a good seal around the unit, minimizing leaks.
U-shaped units: Most window unit air conditioners are boxes that perch on your windowsill. But in the past couple of years, several manufacturers have introduced U-shaped and inverted U-shaped models. U-shaped models sit on the sill, but the window sash slides down into a slot in the top of the air conditioner. That allows you to open the window when the unit is not in use. And just as importantly, it recruits your window to better insulate your room from noise and heat outside. Inverted U-shaped models drape over the windowsill. That configuration offers some advantages in insulation from noise and heat, but the biggest advantage is that these air conditioners block less light. These units have performed well in our tests, but they’re a bit more expensive, and they can be trickier to install. They may not work with all windows, especially those in older homes.
Inverter-powered units: Increasingly, higher-end air conditioners are being powered by a type of compressor known as an inverter. A conventional compressor regulates temperature by running full blast until the desired temperature is reached and then turning off (though the fan continues to run). An inverter turns down and back up without turning off during normal use. There are several advantages to this technology. It’s more energy-efficient. It can be better at maintaining a constant temperature in your room. And finally, inverter units can run more quietly, which is especially important at night when a unit kicking on can often wake you up.
Noise levels: Models that earn high ratings in our noise tests are so quiet that the only sound you might hear is the fan running. Air conditioners that receive lower scores for noise could disturb light sleepers when set on low and are distracting to pretty much everyone when set on high.
Airflow direction: Window air conditioners often do a better job blowing air in one direction than in others. That can be a problem if your window isn’t centered on the wall. To uniformly cool a room, you’ll need to direct air to its center, so check to see whether your AC needs to blow air to the right or to the left to aim toward the center of the room and away from the wall. Some models have fan arms that swivel.
Intelligent cooling: Some air conditioners have gotten smarter, allowing you to control and adjust them from a phone app, so they can turn on or up just before you arrive home instead of staying on all day. You may even be able to interconnect them with other cooling units in your home.
Length of warranty: Some air conditioners have longer warranties than others. When you’re buying a new unit, check the manufacturer’s website for information, and ask the retailer about the warranty for the brand and model you’re considering.
Installation and Maintenance Tips
Install your air conditioner correctly: To get the most value and performance from your window air conditioner, it must be properly installed. Most units are intended for double-hung windows. If you have casement windows, consider buying a through-the-wall air conditioner.
Make sure your window unit is level so that it drains correctly and that you use all the brackets and other hardware to keep your unit secure, as well as to reduce noise and vibrations. Move any heat-generating devices, such as a TV or lamp, away from the unit and use foam and weather stripping to help keep the cool air in your room and the hot air outside. U-shaped units often need special brackets and may not fit on all windows. For more information, read our AC installation tips. Do you live in an apartment? You may have to take some extra steps, such as getting permission from your landlord, before you install an AC in your apartment.
Check the filter location when shopping: To keep your unit running at peak efficiency, AC filters need to be cleaned quite frequently: as often as once a week during peak cooling times, and maybe once a month when the unit isn’t used as much. When selecting a model, make sure you can easily access the filter for cleaning or replacement when the unit is installed. The easier it is, the more likely you are to do it.
How We Test Room ACs
At Consumer Reports, we test room air conditioners in a special climate-controlled chamber. We test three sizes of window ACs—small, medium, and large—and adjust the size of the chamber based on the room size each air conditioner is designed to keep cool. We crank the temperature in the chamber up to 90° F, then measure how long it takes the AC to lower the temperature by 10° F.
We also gauge how well the AC holds the set temperature. And because noisy air conditioners can be annoying, we measure how loud each unit is on its lowest and highest settings.
In addition to our performance tests, we ask CR members about room air conditioners they own. Our current ratings for predicted reliability and owner satisfaction, available to members, are based on results for 6,209 room air conditioners purchased new between 2012 and 2022. Read more in "The Most and Least Reliable Room Air Conditioners.”
Which Model Is Right for You?
Some small window units cost less than $200, which makes them a tempting proposition—but only if you need to cool a very small space. If you need to cool a larger area, you’ll want to focus your search on units that better match your square footage.
Almost all the window units we test meet the latest Energy Star standards, which require models to be at least 10 percent more efficient than those without that certification. Standout models have quiet operation and convenient controls, and they work under brownout conditions. Check our air conditioner ratings to see how models stack up.
Window Air Conditioners
Small: Capacity ranges from 5,000 to 6,500 Btu, and these units cool roughly 100 to 250 square feet. They’re the smallest, lightest, and least expensive units, but they can’t adequately cool a room measuring more than 300 square feet.
Cost: $150 to $350 and up.
Medium: Capacity ranges from 7,000 to 8,200 Btu, and these models cool roughly 250 to 350 square feet. Prices start creeping up, and their size and weight can make them more difficult to install and remove for winter storage.
Cost: $250 to $450 and up.
Large: Capacity ranges from 9,800 to 12,500 Btu, and these units cool between 350 and 550 square feet. They’re best for cooling a large room, but the bulk and weight make these models awkward and difficult to install.
Cost: $350 to $600 and up.
Portable Air Conditioners
Portable models are intended for homes in which window configurations or building regulations prevent installation of conventional window units. The portable air conditioners in our tests range from 9,000 to 15,500 Btu. But don’t compare portable and window air conditioners by that measurement alone.
Our latest air conditioner tests find that portables aren’t nearly as good at cooling as manufacturers claim. Plus they’re pricey and use more energy than similarly sized window units. Because all the mechanicals are sitting in the room, they tend to be noisier than window-mounted units, as well. Finally, “portable” is a misnomer—their 50- to 80-pound weight can make them cumbersome and ungainly to roll across carpets or thresholds.
Cost: $350 to $800.
Split Ductless Air Conditioners
A split ductless system is a smart way to add air conditioning to a limited number of rooms without having to open up walls to install ductwork—as you would with a central-air system—or install and remove multiple window units each year. We currently are evaluating a number of ductless models in our labs. In our past tests they all did an excellent job cooling and were much quieter indoors and out than window air conditioners.
A split ductless system is pricier than window or portable units (and professional installation is recommended) but less expensive than central air if you are cooling only a few rooms. However, if you are looking to cool the majority of your home, a central air-conditioning system is probably the more cost-effective choice.
Cost: $1,000 and up.
Video Buying Guide
For more information, watch our buying guide below.
Smart Features to Help You Chill Out
Many of the units in our air conditioner ratings do a good job of cooling. Highly rated air conditioners may come with convenient features such as digital displays, built-in timers, and remote controls. Some units have touchpad controls, and a few change the direction of the airflow automatically to better disperse cool air throughout the room.
Easy-to-Use Controls
Touchpads with large LED displays, sizable and uncrowded buttons, clear labeling, and digital temperature readouts tend to be easier to use. Poorly designed controls are a constant annoyance. Raised buttons with different shapes let you identify functions by feel. And digital temperature readouts provide a more precise reading than the simple “warmer” and “cooler” settings.
Directional Airflow Vents
Air conditioners have louvers you can adjust to direct airflow vertically or horizontally. Some have fans that oscillate. But most are better at directing air toward one side or the other. Consider your room layout, and look for a model that can direct the airflow toward the center of the room where you need it most and away from a nearby wall or window.
Efficiency Aids
An air conditioner with a timer can be turned off when you’re out or set to turn on just before you expect to get home. An energy-saver setting stops the fan when the compressor is off. These features save electricity.
Dehumidifying Mode
This feature is useful on humid but cool days in spring and fall.
Fresh-Air Intake or Exhaust Setting
This feature provides ventilation without cooling.
Programmable Timer
One common energy-saving feature is a 24-hour programmable timer, which allows you to customize your unit’s operating schedule.
Remote Control
A remote control allows you to adjust the settings from wherever you’re sitting. Some units have built-in temperature sensors to relay the room’s temperature (as opposed to the temperature at the unit itself).
Easy-to-Use Controls
Touchpads with large LED displays, sizable and uncrowded buttons, clear labeling, and digital temperature readouts tend to be easier to use. Poorly designed controls are a constant annoyance. Raised buttons with different shapes let you identify functions by feel. And digital temperature readouts provide a more precise reading than the simple “warmer” and “cooler” settings.
Brands
All the brands below make window air conditioners that are Energy Star certified.
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