Window air conditioners provide effective room cooling in rooms or apartments without access to central HVAC systems. To set up, all you need is an appropriately-sized window (or wall space), a warm room, and an urge to relax in a cool environment on a hot summer day.
They're more energy efficient and eco-friendly than other room ACs. Look out for Energy Star-rated window ACs for energy- and money-saving operation. For easy access to the topics in this window AC buying guide, use our topic list below:
- About Window ACs
- Energy Efficiency
- Size Considerations
- Installation
- Special Features
- Eco-Friendly Refrigerants
- Safety and Security
- Maintenance
About Window ACs
Window air conditioner models are self-contained cooling systems designed to cool one or two rooms. Traditionally, these units mount semi-permanently inside standard vertical sash or double-hung windows or permanently inside a measured and prepared wall opening.
A window air conditioner contains the three basic parts: a compressor, condenser coil, and an evaporator coil. A standard window AC also features two motorized fans, an expansion valve, air filter, manual or digital thermostat, and control panel. To cool your room air, they use refrigerant, a chemical compound that is used in cooling systems to absorb heat from its surroundings.
All models cool by extracting hot and humid air from a room, cooling and dehumidifying it, and returning it back into the room while exhausting warm air to the outside. In more technical terms, a window air conditioner uses its compressor to compress refrigerant into a hot, high-pressure gas. The refrigerant gas then travels through the condenser coil, where it is condensed into a liquid and sent through the expansion valve and over the evaporator coil to absorb heat and cool down. Hot air is exhausted out through the back of the air conditioner — the part facing the outside — while cool air is blown into your room using the air return grille located on the front of the system.
Energy Efficiency
People generally use window air conditioners as the primary source of cooling for spaces that aren't covered by a central AC. However, some customers use them as a way to supplement central AC and avoid running their HVAC system too much during warm months. This can help save money on energy costs. For other energy-savings, look at your model's:
Energy Star Seal
Energy Star room air conditioners use at least 10% less energy than conventional models. These systems are often loaded with useful features to give you greater temperature control and make energy consumption easier to manage. Look for models with digital thermostats, programmable timers, automatic cooling modes, and multiple speeds.
Energy Efficiency Ratio (EER)
An EER measurement is another efficiency indicator, and it's gaining popularity across the window AC industry. This ratio tells you how many British Thermal Units (BTUs) of heat energy a window AC uses for each watt of power. As a rule of thumb, remember the higher the EER, the more efficient the air conditioner.
Typically, every 0.1 increase in EER translates into a 1% drop in your electricity usage. The U.S. Department of Energy recommends a model with an EER of at least 10.0. Window ACs manufactured by Friedrich and Sunpentown are known for both their high EERs and Energy Star seals.
Cooling Capacity
The cooling capacity of a room air conditioner is measured in BTUs (British Thermal Units) per hour. To ensure high efficiency, choose an air conditioner with a BTU level designed to fit the square footage of your room or space.
If you use a window air conditioner that doesn't have enough BTU power to cover a large room, it will work overtime to try and bring the temperature down. In the process, it will waste energy dollars. In contrast, a window AC that has too large of a BTU capacity for your space will cool it, but it won't remove as much humidity from the air as a properly sized unit should. This will make your room feel damp and clammy.
To find the right cooling capacity for your room, determine the square footage of your space. Then, use the chart below to find your ideal BTU measurement.
| Window AC Sizing Chart | |
|---|---|
|
Square Footage of Your Space |
BTUs Needed (per hour) |
100 to 150 sq. ft. |
5,000 BTUs |
150 to 250 sq. ft. |
6,000 BTUs |
250 to 300 sq. ft. |
7,000 sq. ft. |
300 to 350 sq. ft. |
8,000 sq. ft. |
350 to 400 sq. ft. |
9,000 sq. ft. |
400 to 450 sq. ft. |
10,000 sq. ft. |
450 to 550 sq. ft. |
12,000 sq. ft. |
550 to 700 sq. ft. |
14,000 sq. ft. |
700 to 1,000 sq. ft. |
18,000 sq. ft. |
1,000 to 1,200 sq. ft. |
21,000 sq. ft. |
1,200 to 1,400 sq. ft. |
23,000 sq. ft. |
1,400 to 1,550 sq. ft. |
25,000 sq. ft. |
Ceiling Height — The above estimates assume you have traditional 8-foot ceilings. If your ceilings measure higher than 8 feet, you'll want to increase your BTU level.To determine the most accurate BTU estimate, you should also consider these factors:
- Sunlight — If your room or space is sunny during the day, increase your BTUs by 10 percent.
- Shade — If your room is shaded for most of the day, decrease your BTUs by 10 percent.
- Number of Occupants — If more than 2 people will occupy your room or space regularly, you should add an additional 600 BTUs of cooling power for each person.
- Kitchen — If you are installing your window AC in a kitchen, increase the BTU level by 4,000.
Installation Type
When deciding among window air conditioners, you should also consider where you're installing it. The most popular window AC models are designed to fit inside double-hung — or vertical opening — windows, but there are a few options.
Window Installation
When installing a window AC in a double-hung window, you'll need to measure the dimensions inside your window frame exactly, paying special attention to the width. With these measurements in hand, look for the minimum and maximum window width dimensions listed in the air conditioner's specifications. Don't worry if the window AC doesn't extend to fit your window frame exactly. All window ACs come with installation kits, which include adjustable side curtains to seal any extra space left on each side of the window opening.
For step-by-step directions and an informational video on how to install a window AC, check out our Window Air Conditioner Installation Guide.
Through-Wall Installation
If you plan to install one through your wall, first make sure the unit you want can accommodate this type of installation and that you have the appropriate installation kit. Not all window ACs can be installed through a wall. Check the specifications to see if your model has ths installation option.
Then, make note of the dimensions of the finished wall opening, which should be listed in the owner's manual. Use these dimensions when creating your wall opening. If necessary, consult a professional when attempting to install your window AC through a wall.
Once it's completely installed — whether in a window or through a wall — the window air conditioner should sit level inside the opening, with the warm air exhaust system facing outside and the cool air return system facing inside. Some models, such as Friedrich window air conditioners, incorporate a slide-out chassis and rugged mounting sleeves that help stabilize each unit while giving you easy access for maintenance. Be sure to follow the manufacturer's installation instructions, which will be included with your unit.
Electrical Requirements
Window ACs are more powerful than other common household appliances. Because of this, you will need to make sure your existing electrical system meets the needs of the unit you choose. Most room air conditioners operate on 115-, 125-, or 220-volt circuits. Air conditioners that have cooling capacities below 15,000 BTUs usually run on 115- or 125-volt circuits. This is the norm for outlets in most bedrooms and living rooms. Window ACs with cooling capacities above 15,000 BTUs usually run on 220-volt circuits.
With these models, you may need to install special electrical wiring or hire an electrician to do this for you. Electrical measurements — including voltage, amps, and watts — will be listed in an AC's specifications. Additionally, the correct plug face type may be pictured or listed by its National Electrical Manufacturers Association (NEMA) classification.
Additional Features
Along with the main window AC considerations, you'll find yourself weighing the benefits of many "nice-to-have" features as you peruse window AC models. These functionalities are in place to give you more control over your unit's operation and, in some cases, to boost operational efficiency. Most models come with digital controls and remotes, but some models have manual dials.
Many window air conditioners are equipped with additional operating modes, making these models perform double- or even triple-duty in your environment. These can include fan-only settings for ventilation, independent heating modes, dehumidifier modes, and air purification modes.
Most room air conditioners feature basic air filters that help remove large particles from incoming air that might otherwise get caught in the system and affect operation. These filters get more advanced at higher price points, and some may also remove odors and smoke as well as airborne germs. Mosquito traps are protective screens that work in the same manner, preventing mosquitoes and other bugs from entering the AC — and your room — from the outside.
ACs like the Friedrich Chill CP10G10A have adjustable louvers, which you can adjust horizontally and vertically to make air flow in multiple directions. This gives you better air circulation throughout your space. Programmable timers allow you to set timed operation and manage energy consumption. Remote controls give you the convenience of selecting and setting functions from a distance.
Eco-Friendly Refrigerants
In January 2010, the U.S. Environmental Protection Agency (EPA) began requiring air conditioner manufacturers to use eco-friendly refrigerants in their new air conditioner models, including central ACs, portable ACs, and window ACs. This decision is part of a larger program designed to protect the Earth's ozone layer by phasing out ozone-depleting HCFC (hydrochloroflourocarbon) refrigerants, which have contributed to significant ozone depletion over the South Pole.
One of the most common HCFC refrigerants used in air conditioners is HCFC-22, also known as R-22. The R-22 refrigerant has now been replaced by non-ozone-depleting R-410A refrigerant. All major AC manufacturers have begun using eco-friendly refrigerant in new AC models.
Safety and Security
Window air conditioner units have become safer to install and operate over the years with the introduction of sturdier window kits, electrical safety plugs, and current-protecting power cords. Be sure to follow the manufacturer's installation instructions closely when installing your window AC in a window or through a wall. If installed correctly, the AC unit should sit firmly and securely within the space without any opportunity for shifting. Often, you might need to use extra window brackets for sufficient support in your window. These can be purchased separately.
Safety becomes an issue when a window air conditioner is improperly secured or you use loose objects to support it. Setting objects on top of the housing is also discouraged. These objects may include things like bricks, wooden blocks, flower pots, satellite dishes, and/or birdfeeders. Safer current-protected electrical cords and polarized plugs drastically reduce the risk of electrical shocks during operation. Adding extension cords is not recommended.
To deter intruders, some window ACs are equipped with anti-intrusion protection systems. These systems are constructed of steel retaining wire that secures the chassis to the mounting sleeve in order to deter a "kick-in" intrusion.
Maintenance
To maintain effective and long-lasting operation, clean your window AC thoroughly at least once per year. Don't wait until you detect faulty operation. Window air conditioners that feature slide-out chassis make maintenance convenient because all you have to do is slide the unit out to access it. For maintenance tips and procedures, refer to your AC's owner's manual. Lots of times, all you have to do is use a vacuum crevice tool and a soft brush to sweep dust and dirt away from the internal components. Most air filters are easily washable with soap and water.
Still Have Questions?
For more information on specific window air conditioners and other ways to improve your indoor air, browse our products and visit our Knowledge Center. Not sure what's best for you? We can take the guesswork out of decision-making. Contact our product experts toll-free at 1-800-934-9194. We want to help make your indoor environment healthy and comfortable.
