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An introduction to window air conditioners

For most homes, the simplest and cheapest way to cool your home is with a window air conditioning unit. Typically costing between $100 and $350, these air conditioners don't require professional installation (though they are heavy, so a little help from a friend is a good idea). Central air conditioners, by contrast, can cost a few thousand just for the equipment, plus installation costs. Portable air conditioners cost between $300 and $500, and they don't cool as efficiently as window units; they're only a good choice for those who can't install a window air conditioner.

Although room-sized air conditioners are most often installed in a window, some can be permanently mounted in a wall. However, this type of installation is much more complex and typically must be done by a professional. We found no professional reviews, and few user reviews, for wall-mounted air conditioners, so this report focuses specifically on window units.

When choosing a window air conditioner, the most important factor to consider is size. Experts agree that it's crucial to match the size of the unit to the size of the space you wish to cool. Smaller units tend to be less expensive than their larger counterparts, but they won't pack enough punch to cool a large room. On the other hand, don't fall into the trap of buying more air conditioner than your space really requires. "Too much capacity and the unit will cycle on and off too often, wasting energy," cautions the American Council for an Energy-Efficient Economy (ACEEE).

Moreover, ConsumerReports.org adds that an oversized air conditioner will cool the room too fast to remove humidity from the air, leaving the room chilly and damp. The Energy Star website, run by the Environmental Protection Agency, offers useful guidance on how to determine what size unit you need.

As long as you choose the right size for your space, experts say, most modern window air conditioners do a pretty good job of cooling a room. However, air conditioners can differ widely in how well they distribute the cooled air. Tests at ConsumerReports.org show that most units do a much better job sending air in one direction -- right or left -- than the other. Air conditioners also differ in efficiency. The energy efficiency ratio (EER) of an air conditioner is simply its cooling output, measured in British thermal units (Btu), divided by its power use in watt-hours. The higher the EER, the less your new air conditioner will jack up your utility bill.

One simple way to find more efficient products is to look for the Energy Star label. Air conditioners that carry it will be at least 10 percent more efficient than those without it, and they only cost a bit more up front. All models covered by ConsumerSearch meet Energy Star standards.

After performance and efficiency, the most important factors to consider in choosing an air conditioner are noise level and ease of use. Noise is particularly important when choosing a unit for your bedroom, and ease of use includes such factors as simple controls, an easy-to-read display and easy installation. ConsumerReports.org rates window air conditioners on both factors, and they also show up frequently in owner-written reviews at retail sites such as Walmart.com, Amazon.com and Lowes.com. In addition to these, we considered overall value when choosing our recommended models. This includes not just the price of the unit but also how durable it is and the strength of the manufacturer's warranty.

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