The smallest and least expensive portable air conditioners are 7,500- and 8,000-BTU (British thermal unit, which is a measure of cooling power) units that can cool 150- to 200-square-foot rooms like small bedrooms. With portable units, you need a higher BTU rating than you would with a window air conditioner to cool the same amount of space. (See our What to Look For page for a sizing chart.)
Owners say the 8,000-BTU MobilComfort KY-80 (*Est. $260) is one of the better choices among smaller portable air conditioners. It has separate cooling and dehumidifier functions, and owners particularly appreciate its remote control and timer feature. Yet the biggest positive is that the KY-80 seems to do best what matters most -- cooling a room. Few if any portable air conditioners in its class do as well in that regard, based on customer feedback. Installation is also fairly easy, most say, helped along by a high-quality window installation kit and reasonably easy-to-follow instructions. However, one or two reviews complain that the exhaust hose is difficult to attach to the unit.
There are other downsides, as well. Opinions are split as to whether the KY-80 is noisy or relatively quiet. Most reviews saying that it's loud complain specifically about the fan continuing to run even after the desired temperature is reached. Several owners complain that the built-in drain pan fills up too quickly with condensed water; an alarm is supposed to sound when it's time to dump it, but some say it never does and the unit just overflows. While most say that the unit's slim profile is a plus, at least one owner grouses about its bulk. Some had trouble getting the display to revert back to Fahrenheit after inadvertently switching it to Celsius.
If the room you want to cool is a little larger -- say 250 square feet or so -- user reviews indicate that the 10,000-BTU NewAir AC-10000E (*Est. $350) is a good choice. It's also a relative bargain, costing less than most portable air conditioners meant to be used in a room this size.
Feedback on the AC-10000E is positive overall, and not just because of its attractive price. It's relatively compact, and it includes controls on the air conditioner itself. Many portable AC units with remote controls omit on-unit controls, which can quickly get frustrating if the remote is mislaid. Noise, however, seems to be a big drawback with the AC-10000E. Even positive reviews say this portable air conditioner is extremely loud, not only when cooling but also when the controls are used. Also, some owners say the unit's display is too bright to use in a dark bedroom, to the point that some owners cover the display with duct tape or fabric.
Most reviewers say the NewAir AC-10000E does an excellent job of keeping appropriately sized rooms comfortable -- even "downright cold," in one owner's remarks -- although some say it either didn't work at all or only cooled the air by a few degrees. The NewAir AC-10000E uses self-evaporative technology to disperse most (if not all) collected condensation. While most owners say that works fine, others disagree. One reviewer says that even a 5-gallon bucket placed underneath the unit had to be emptied during the night. However, these are common complaints with most of the portable air conditioners we researched, and the NewAir AC-10000E attracts more positive reviews than any other 10,000-BTU unit. The NewAir AC-10000H (*Est. $380) adds a space-heater function but is otherwise identical. It gets similarly high ratings.
For bigger spaces you need an even more powerful portable air conditioner. One option is the 12,000-BTU NewAir AC-12000E (*Est. $430), which can cool a 350-square-foot space. While the majority of owners are pleased with the unit's cooling ability, some say it's only mediocre. We also saw a few reviews that questioned the AC-12000E's reliability, adding that their portable unit either stopped working shortly after purchase or never worked out of the box. However, the most common complaint found in user reviews is that the NewAir AC-12000E is on the loud side.
Despite these contrary opinions, a clear majority of owners seem to be largely pleased with this portable air conditioner's performance and features. The most common positive cited is the NewAir AC-12000E's easy installation, which is particularly useful for those who intend to move this portable unit from room to room, or to uninstall it completely during cooler months. Many appreciate the remote control, and some also give a thumbs-up to the 24-hour timer. The auto-evaporative system seems to work better on this model than on the less powerful NewAir AC-10000E (discussed above), so owners rarely need to discard any accumulated moisture. The NewAir AC-12000H (*Est. $460) is the same portable air conditioner, but with an added space heater feature. Owners rate it similarly to the NewAir AC-12000E.
The Whynter Eco-friendly ARC-12S (*Est. $410), is another consideration. It has a lot in common with the NewAir AC-12000E: both pack 12,000 BTUs of cooling power (suitable for 350-square-foot spaces), remote controls, 24-hour on/off timers and auto-evaporation features that work well in reviews (so you won't find yourself constantly dumping buckets of water). The Whynter Eco-friendly ARC-12S is a bit more efficient than the NewAir AC-12000E, with an energy-efficiency rating (EER) of 11.1 versus the NewAir's 10.2. However, its "Eco-friendly" name comes from the fact that it uses the more ozone-friendly R-410A refrigerant instead of regular Freon. Freon has been banned in new air conditioners in the U.S. since 2010, so all new air conditioners are equally eco-friendly in that respect.
The Whynter ARC-12S gets overwhelmingly high marks from happy owners at Target.com, HomeDepot.com and Meijer.com, who say it does a great job cooling the advertised space. However, plenty complain that it's extremely noisy (a problem with most portable air conditioners, including the NewAir models). And a sizable minority -- especially at Amazon.com -- say they got a dud that wouldn't work at all, wouldn't blow cold air or broke quickly. These complaints are common enough to relegate the Whynter Eco-friendly ARC-12S to runner-up status compared to the NewAir AC-12000E, but it is a close call.