Think of portable air conditioners as the cooling choice of last resort. They’re better than a fan but not much. That’s what Consumer Reports discovered in its tests of eight portable air conditioners that, despite their claims, barely got a room below sweltering let alone the 78 degrees that’s considered the upper threshold of indoor comfort.
Portable air conditioners are intended for homes in which window configurations or building regulations prevent installation of window units. But getting one is a compromise you may not want to make because they’re typically bigger, noisier, more expensive, and use more energy. In fact, retailers report that many portable air conditioners are returned each season by dissatisfied customers.
How they work. Unlike a window air conditioner, all the mechanical parts of a portable air conditioner are sitting in the room you’re trying to cool. This contributes to the noise and less-than-capable cooling, as the portable unit is using conditioned air from the room to cool the condenser and exhausts the hot air out an ungainly exhaust hose that resembles a dryer vent. That creates negative pressure causing unconditioned warm air from surrounding rooms or outdoors to be drawn into the room you’re trying keep cool.
Typical window installation
How portable? And it’s debatable how portable they are, since once the hose is connected to the kit in the window, you won’t want to move the unit, especially since they typically weigh 50 to 80 pounds. While they do have wheels, portable air conditioners can be difficult to roll on carpets and over raised thresholds between rooms. They also need their space—the hose is 5 to 7 feet long and the air conditioner must be positioned away from any walls or furniture that may block its airflow.
How we test. In our tests, we measured how long it takes a portable air conditioner to lower the temperature in a room appropriate for its claimed size from 90 degrees to 75. But few made it to even 80 after 100 minutes. None made our list of recommended air conditioners but if you have no alternative, consider the Honeywell MN10CES[WW], $400, for its lower price. While only fair at cooling, it was a champ in our tests simulating brownout conditions, as were four other models.
While we test portable air conditioners the same way we test window units, most manufacturers don’t. The Department of Energy is reviewing the current industry test for portable air conditioner capacity and efficiency. The current test doesn’t account for what is often significant leakage and transfer of hot air into the space being cooled. One alternative being investigated by the DOE is that the industry adopt the window air conditioner test for portables as well, because it more accurately measures actual cooling. This would make it easier for consumers to compare portable and window air conditioners. In the meantime. don’t assume that a portable air conditioner rated at 5,000 to 15,000 British Thermal Units will cool like similarly rated window models.
If a portable is your only choice Install it right. All portables come with a kit that you install in a window. Make sure all your connections are tight and seal any air gaps. Get a ceiling fan. Create a cool breeze by running a ceiling fan. Block the sun. Close the curtains and shades to keep the sun from overheating your room.
The best window A/Cs from our tests
When buying a window air conditioner, make sure you get the right size air conditioner for your room. Too small and you’ll be uncomfortable, too big and your room will cool too quickly without removing enough moisture from the air, leaving you cold and clammy. Here’s the top performer for each size.