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Comparing portable and window air conditioners

A portable air conditioner is a compact air conditioning unit about 3 feet high and 18 inches wide. It exhausts hot air from the room through an attached hose, which can be run out a window or through a wall. Unlike a window air conditioner, portable units are mounted on casters so they can be rolled from room to room. It can also be installed without any heavy lifting, and it's easy to store away in the off-season.

However, experts caution that portable air conditioners don't match the performance of window air conditioners. In fact, according to ConsumerReports.org, portable units are inferior in nearly every way. They can't cool a room as effectively as a similarly sized window unit, and most can't cool as large a space as their manufacturers claim. They also use more energy than window units, and because all the mechanical parts are inside the room, they're noisy as well. In addition, portable units tend to be pricier. The portable air conditioners covered in this report range in price from around $300 to $500. By contrast, the Best Reviewed models in our report on window air conditioners cost no more than $325.

For those living in apartment buildings that don't permit window units, however, a portable air conditioner may be the only option. If you're in that position, the experts at ConsumerReports.org recommend a portable unit with a dual-hose design. One hose brings in outside air to cool the condenser, and another exhausts heated air. The editors say this type of air conditioner performed better in their tests than single-hose models, which draw air in and vent it back out through the same hose. However, we found good reviews from users for both single-hose and dual-hose units.

Like other air conditioners, portable units remove moisture from the air as they cool. With a window air conditioner, getting rid of the water is easy; it simply drips down from the rear of unit, which hangs outside. With a portable air conditioner, the process is a bit trickier. Some units have an internal tank for moisture, which must be emptied frequently. These units are designed to shut off automatically when the tank is full -- but users warn that this feature doesn't always work properly, resulting in puddles on the floor. Other units have a drainage hose that attaches to the air conditioner, allowing water to drip out into a bucket, which you must then empty.

A few models make this feature more convenient by adding a condensate pump so that the drainage hose can be run through a window. Self-evaporation drainage systems, which send evaporated water through the exhaust hose along with the heated air, are the most convenient, reviewers say. However, the reviews we read indicate that in humid climates, this feature generally can't handle all the moisture the air conditioner removes from the air, so users will still need to drain their units manually.

The cooling power of a portable air conditioner is measured in British thermal units (Btu). Models range in power from 5,000 Btu to 14,000 or more. Since portable air conditioners are generally less efficient than window units, you'll need more power to cool the same amount of space. Our sources suggest that for a small room -- up to 200 square feet -- a 7,000- or 8,000-Btu unit may be sufficient. For rooms over 350 square feet, by contrast, you'll need at least 12,000 Btu.

Another figure to look at is the energy efficiency rating (EER) of the unit, which is its capacity in Btu divided by its power use in watts. The higher this number, the more cooling power you'll get for every watt of energy use. The portable air conditioners covered in this report range from 8.5 to 11.6 EER. More efficient models generally cost more, but depending on how much they're used, they may save money in the long run.

We could not find any professional tests of portable air conditioners. ConsumerReports.org has not published a report on them in decades, and we found no other sources that evaluate them in any kind of systematic way. Thus, to evaluate different models, we had to rely on reviews from users at retail sites such as Amazon.com, HomeDepot.com and Air-n-Water.com (a specialty retailer that focuses on compact appliances). In comparing these reviews, we focused on three main criteria.

Since an air conditioner's main job is to keep you cool, we looked first at cooling performance. In addition to looking at how well each unit cools the room, we also gave some attention to its efficiency and noise level. Next we considered ease of use. This includes such factors as setting up the unit, using the controls, draining out condensate and maintaining the unit. Finally, we looked at value. This means not just the price of the unit but also how durable it is and how good a warranty comes with it.

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