How to Buy the Right Window or Room Air Conditioner | HomeTips
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How to Buy the Right Window or Room Air Conditioner

This expert, unbiased air conditioner buying guide will help you choose the best room or window AC unit. It includes advice on available types and features, and how to size an AC unit.

Today’s window and room air conditioners are quiet-operating marvels of design that can do an excellent job of cooling rooms or confined spaces. The trick when buying a new room air conditioner is to select a model that is suited to your room, and will handle the job affordably, efficiently, and reliably.

Compared to a whole-house air conditioner, room air conditioners are more affordable to operate if you just want to cool one or two rooms. They are also the most sensible option if you don’t own the property, or you don’t want to spend the big bucks for a whole-house system. For more about comparing the advantages of room and whole-house air conditioners, see Is Central Air Conditioning a Smarter Choice Than Room AC?

Window air conditioner installs quickly and easily and provides effective cooling for one room.

There are many energy-efficient models with a range of features, from digital thermostats to remote controls and variable fan speeds. This is an unbiased window and room air conditioner buying guide, including information on types and energy-efficiency.

Advantages of Room AC

About one-quarter of American households have in-room air conditioners, and the numbers are increasing. The factors that are helping to drive this popularity include:

Affordability. Small models cost as little as $100. Large room air conditioners, with greater cooling capacities, can run up to $700.

Efficiency. Many units have variable digital controls instead of the simple HIGH and LOW settings of earlier models. Units with energy-saver switches provide further help in cutting down on utility costs.

Availability. Window and room air conditioners are sold at most big-box home improvement stores, as well as at large supermarket chain stores, department stores, and even pharmacies. Frigidaire, GE, Kenmore and LG are among the top-selling brands.

Easy Installation. Most window air conditioners come with easy-to-use installation kits. Free-standing portable ACs need minimal setup and can be moved from room to room.

Easy Hook-Up. You just plug them into a receptacle, though some require electrical improvements. Relatively small room air conditioners, such as those that draw less than 7.5 amps of electricity, can simply be plugged into a standard receptacle that isn’t shared with other major appliances. Larger AC units require a dedicated 120-volt circuit—in fact, the largest models need a 230-volt dedicated circuit. Take these electrical needs into account when you select a model.

Types of Room AC

Window-mounted AC unit is easy to install and designed to fit many sizes of double-hung windows or in openings framed in an exterior wall. Photo: Frigidaire

There are three main types of room air conditioners: window units, wall-mounted units, and portable models. They type that suits your room is often dependent on the installation possibilities—whether a unit can be fitted in a window, can be built into a wall, or must be more portable. For information on a related type of room air conditioner, see Ductless, Mini-Split Air Conditioners.

Window Air Conditioners

Window units are by far the most popular. Models can be installed in most single- or double-hung windows and typically come with accordion panels that make for a secure fit. Some are also designed to fit in sliding windows.

Installing a window unit is a relatively easy DIY project, as discussed in the article How to Install a Window Air Conditioner. Make sure you measure the inside window dimensions before you shop. Directions and hardware should be included.

Through-the-Wall Air Conditioners

Through-the-wall units require opening a hole in an exterior wall, a job that is considerably more involved than installing a window unit.

Portable AC units can roll from one room to the next, though they do require a flexible duct to exhaust through a window. Photo: Whynter

On the plus side, they don’t take up window space, and they allow for a more airtight and secure fit. Most window models can be adapted for installation as through-the-wall units—you just add a frame to support the unit. Though large units may require professional installation, small through-the-wall air conditioners can be installed by handy do-it-yourselfers.

Portable Air Conditioners

Portable air conditioners are self- contained, freestanding units. Most have casters, so they can be wheeled around to the room or rooms that need to be cooled. They come with a large, flexible hose that is attached to a window for exhausting hot air, much like the way a clothes dryer is vented. Though the appliances tend to cost more than window and through-the-wall units, they are much easier to install and practical because of their portability.

Room AC Energy Efficiency

Because room air conditioners use a lot of electricity, all new room air conditioners are required to carry an EER, or Energy Efficiency Rating, which measures the appliance’s ability to convert energy to cooling. The higher the EER, the better. Though air conditioners built before 1991 may have an EER of 5, newer AC units are required to have EER of 8.0 or greater. Energy Star® qualified units have ratings as high as 11.5.

A high EER also helps the environment by reducing greenhouse emissions. Check the yellow Energy Guide® label on new room air conditioners when you’re shopping. An EER of 10 takes half the energy of a 5 EER.

One of the best ways to ensure efficiency is to buy the right size window, wall, or room air conditioner. For an explanation of how to size one of these units, along with a sizing chart, see Sizing a Room Air Conditioner, below.

These energy-efficient features contribute to a strong EER and offer greater convenience and comfort:

Variable Fan Speeds. More speed settings give you greater control of air flow, which also helps save money.

State-of-the-art AC units offer easy-to-use digital controls with energy-efficiency settings. Photo: Frigidaire

Digital Temperature Control. The ability to control temperature by degrees—instead of with simple HIGH or LOW settings as previous models had—allows for greater comfort as well as increased energy savings.

Programmable Thermostat. Though it comes as a premium, you may want to pay a little more for an AC unit that lets you program desired settings for different times of the day and night.

Easy-to-access Filters. Filters remove dust and other allergens from the air. Filters that slide out make cleaning them a snap. Regular maintenance will extend the service life of your air conditioner and keep it operating at full efficiency.

Sleep Setting/Energy-Saving Setting. The unit operates at a very low setting during nighttime hours, making the room more comfortable for sleeping and at the same time saving on energy costs.

Timer. Timers are a simpler and less costly alternative to programmable thermostats. Just set the time you want the AC to start or stop. Timers let you come home to a house that already is cool without continuously running the air conditioner while you’re away.

Sizing a Room Air Conditioner

Before buying a room air conditioner, check its BTU rating to make sure you buy the proper size. (See What Is a BTU? ) Room air conditioners perform best when they are sized properly, so it is essential to pick a unit with a cooling capacity that is right for the room where it will be installed. A unit that is too small may be inadequate to cool a room, but an over-sized air conditioner will cycle on and off, wasting energy, increasing electric bills, straining the unit, and doing a poor job of dehumidifying the air.

Before shopping, measure the dimensions of the room you want to cool. Multiply the length by the width to get the square footage of living space. Then, match the room size with the BTU rating, which should be printed on the packing box. As a rule-of-thumb, figure 20 BTU for each square foot, though this is affected by your climate, window sizes, house shading, and the room’s height.

Room air conditioners operate at 5,000 to 24,000 BTU per hour; 12,500-BTU units are considered large. Expect the cost of the air conditioner to increase as the BTU rating goes up.

Small room air conditioners generally operate at 5,000 to 7,000 BTU per hour and can adequately cool 100 to 300 square feet.

Mid-sized models run at 8,000 to 10,000 BTU per hour. They can cool a room up to 450 square feet. A large unit rated between 10,000 and 12,500 BTU will cool a room sized 400 to 650 square feet. See the chart below for complete recommendations.

Several variables can affect cooling capacity:

• If you live in a very warm climate, you may need an AC unit that outputs more BTU per hour than recommended.

• Add 10% capacity for particularly sunny rooms or subtract 10% capacity for shady rooms.

• If the room you are cooling is permanently open to an adjoining space, figure the square footage of both rooms when calculating the size air conditioner you will need.

• Portable air conditioners generally are not as efficient as window air conditioners, so it is a good idea to get a more powerful unit than the square footage indicates.

AC Buying Advice

Air conditioners remove water from the air as they cool it, which means that most portable units have reservoirs that need to be periodically emptied, though some also come with optional hookups for a drainage hose.

Some new models evaporate much of the moisture and exhaust it, greatly reducing the frequency of need to empty a container.

Before buying, be sure your home’s electrical system can handle the appliance’s power needs. If a dedicated or 230-volt circuit is required, you’ll need to have an electrical contractor install this.
Keep your room’s layout in mind when purchasing a particular model—make sure it will be able to direct cooled air where you want it.

If you’ll be installing the air conditioner at the end of a long room, consider buying a model that has a “Super Thrust” or “Power Thrust” fan control that pushes air further into the room—just be aware that this type of unit will be noisier than standard models.


About Don Vandervort
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Don Vandervort developed his expertise more than 30 years ago as Building Editor for both Sunset Books and Home Magazine. He has written more than 30 home improvement books and countless magazine articles. He appeared regularly on HGTV’s “The Fix,” and served as MSN’s home expert. Don founded HomeTips in 1996.

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1 Comment

  1. I have a circuit panel with 100 Amps. I currently have one window AC unit and am considering installing a second which uswes 4.5 Amps. Both are about 5,000 BTUs and don’t require dedicated circuits. My electrician says my “bus bar” on my circuit panel is full. Why is that relevant? I do not plan on using more than one AC unit at a time.


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