Once a high-priced convenience, relatively precise electronic controls with digital temperature readouts have replaced vague “warmer” and “cooler” settings on a growing number of lower-priced air conditioners. Added efficiency is also trickling down the price scale. No longer do models that use the least electricity cost the most. Most models in our recent tests have a higher Energy Efficiency Rating (EER) than the federal government requires. To have Energy Star status, brands must meet or exceed 10.7 EER. This means a model is at least 10 percent more efficient than the standard. The minimum EER for air conditioners below 8,000 British thermal units per hour (Btu/hr.) is 9.7; the minimum is 9.8 for those with 8,000 to 13,999 Btu/hr.

WHAT’S AVAILABLE

Fedders, GE, Haier, Kenmore (Sears), LG, Maytag, and Whirlpool are the leading brands of room air conditioners. You’ll find cooling capacities that range from 5,000 Btu/hr. to more than 30,000 Btu/hr. The majority of room air conditioners in stores are small and midsize units from 5,000 to 9,000 Btu/hr. Large models (9,800 to 12,500 Btu/hr.) can also be found. Price range: about $100 to $600 (small to midsize, depending mostly on cooling capacity); $200 to $800 (large).

IMPORTANT FEATURES

An air conditioner’s exterior-facing portion contains a compressor, fan, and condenser, while the part that faces a home’s interior contains a fan and an evaporator. Most room models are designed to fit double-hung windows, though some are built for casement and slider windows and others for in-wall installation.

Most models have adjustable vertical and horizontal louvers to direct airflow. Many offer a fresh-air intake or exhaust setting for ventilation, although this feature moves a relatively small amount of air. An energy-saver setting on most units stops the fan when the compressor cycles off. Electronic touchpad controls and digital temperature readouts are also common. A timer lets you program the unit to switch on (say, half an hour before you get home) or off at a given time. Most models also include a remote control. Some models install with a slide-out chassis--an outer cabinet that anchors in the window, into which you slide the unit.

The latest feature on air conditioners is a big new plug to help prevent fires. The plug shuts down power when it senses that the air conditioner cord is damaged. The new plugs are known by different names, including leakage current detection interrupters (LCDI) and arc shields. They have test and reset buttons like those on bathroom and outdoor outlets. The plugs are required by Underwriters Laboratories on units made after July 2004.

HOW TO CHOOSE

These are things to consider:

Assess your room size. A general rule is that 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.

Consider window location. To direct air to the center of the room for uniform cooling, does the air conditioner need to blow more air to the left or right? Most units do a better job directing air in one direction or the other, in part because of the design of the model’s internal fan.

Look for third-party certification. When assessing EER, look for a certification sticker from the Association of Home Appliance Manufacturers (AHAM) or the Canadian Standards Association (CSA). An energy-efficient unit will not only help the environment but may also qualify for rebates in some areas; see the Energy Star Web site, at www.energystar.gov, for details.

Don’t buy features you don’t need. Low-profile models take up less space in your window and can direct air up, not just side-to-side, but they are pricier.

Clean it periodically. With any model, clean the filter biweekly or as needed. Where possible, hose off the back of the unit if debris has clogged cooling coils.