Low prices and high efficiency make room air conditioners an inexpensive alternative to central air for cooling one or two rooms.

Many now cost as little as $100. And all models we tested meet the 9.7 Energy Efficiency Rating (EER) now required for air conditioners below 8,000 British thermal units per hour (Btu/hr.), and 9.8 EER for those with 8,000 to 13,999 Btu/hr. Most room A/Cs also meet or exceed the 10.7 EER needed to qualify for the voluntary federal Energy Star designation.

Digital temperature readouts instead of vague "warmer" and "cooler" settings are another plus on many new air conditioners. Many are also quieter, lighter, and smaller.

WHAT'S AVAILABLE

Frigidaire, GE, Haier, Kenmore (Sears), and LG are the leading brands. Cooling capacities range from 5,000 British thermal units per hour (Btu/hr.) to more than 30,000 Btu/hr., though most are small and midsized models from 5,000 to 9,000 Btu/hr. Large models typically range from 9,800 to 12,500 Btu/hr. Price: about $100 to $600 for small to midsized models based mostly on capacity, and $200 to $700 for larger models.

IMPORTANT FEATURES

An air conditioner's exterior-facing portion contains a compressor, fan, and condenser, while the interior-facing portion has a fan and an evaporator. Most room models are designed to fit double-hung windows, though some fit casement and slider windows, while others are for in-wall installation. Most have adjustable vertical and horizontal louvers to direct airflow. Many models include a remote control and offer a fresh-air intake or exhaust setting for ventilation, although this moves relatively little air. An energy-saver setting on many stops the fan when the compressor cycles off and monitors the temperature. Electronic controls and digital temperature readouts are also common. A timer can switch the unit on or off automatically. Some models are installed with a slide-out chassis—an outer cabinet that anchors in the window. All models now have safer plugs that help prevent fires by shutting down power if they sense the power cord is damaged. Some Frigidaire models include infinitely variable fan speeds, while some Haier and LG units have a dehumidifying mode that's useful on humid but cool days in spring and fall.

HOW TO CHOOSE

Here are some tips for choosing an appropriately sized air conditioner that combines performance, efficiency, and value:

Determine the cooling you need. A general rule: 5,000 to 6,000 Btu/hr. models cool rooms 100 to 300 square feet; 7,000 to 8,200 Btu/hr. models cool rooms 250 to 550 square feet; and 9,800 to 12,500 Btu/hr. models cool rooms 350 to 950 square feet. Room construction, climate, and other factors also affect your choice.

Try out the controls. Look for touchpads with large LED displays, clear labeling, and conveniently placed buttons. Raised buttons with different shapes for different functions are easier to use and identify by touch than tiny or crowded ones.

Consider window location. Nearly all air conditioners do a better job directing air in one direction or the other. To direct air to the center of a room for uniform cooling, see if the air needs to blow to the right or left, then see our Ratings.

Look for third-party certification. For Energy Efficiency Ratings, look for a qualification sticker from the Association of Home Appliance Manufacturers (AHAM) or the Canadian Standards Association (CSA). An efficient A/C helps the environment and may qualify for rebates (see www.energystar.gov for details).

Copyright © 2003-2007 Consumers Union of U.S., Inc.

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