Getting started

Low prices and high efficiency make room air conditioners an inexpensive alternative to central air for cooling one or two rooms. Some 5,000- to 6,000-Btu units now cost less than $150. Our air-conditioner guide will help you choose what's right for you.

All the models we tested meet the 9.7 Energy Efficiency Ratio (EER) now required for small and medium-sized models below 8,000 British thermal units (Btu) per hour, and the 9.8 EER required for larger, 8,000- to 13,999-Btu models. Most also meet or exceed the 10.7 EER needed to qualify for Energy Star. And all now have electrical plugs that help prevent fires by shutting down if the power cord is damaged.

Find out whether replacing your air conditioner makes sense by using the savings calculator on the room air conditioners page at

www.energystar.gov. (Every 0.1 increase in EER translates into about a 1 percent drop in electricity use.) Also keep the following in mind:

. (Every 0.1 increase in EER translates into about a 1 percent drop in electricity use.) Also keep the following in mind:

An air conditioner that's too small won't do a good job cooling a room. One that's too big cools the area so quickly that it doesn't have time to remove enough moisture, so it leaves you with a cold, clammy room.

Models that scored excellent or very good in our noise tests are so quiet that the only sound you might hear is the fan running. But air conditioners that scored fair for noise could disturb light sleepers when set on low and are distracting on high.

Air conditioners generally do a better job blowing air in one direction than in the other. 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 whether your A/C needs to blow air to the right or to the left.

Types

Most room models are designed to fit double-hung windows. Some fit casement and slider windows, and some are made for through-the-wall installation. To determine the proper size, measure the square footage of the area you want to cool. Increase capacity for a kitchen or a room usually occupied by more than two or three people.

Capacity ranges from 5,000 to 6,500 Btu/hr. Cool roughly 100 to 300 square feet.

Midsized air conditioner Capacity ranges from 7,000 to 8,200 Btu/hr. Cool roughly 250 to 400 square feet.

Capacities range from 9,800 to 12,500 Btu/hr. Cool roughly 350 to 650 square feet.

Features

All the air conditioners in our Ratings do an excellent job of cooling. They also have such convenient features 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. Look for air conditioner features that affect performance and efficiency.

Air conditioners generally have louvers you can adjust to direct airflow vertically or horizontally. 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 where you need it.

Touchpads with large LED displays, large and uncrowded buttons, clear labeling, and digital temperature readouts are 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 traditional "warmer" and "cooler" settings.

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 energy.

This feature is useful on humid but cool days in spring and fall.

It provides ventilation without cooling.