A portable air conditioner.

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 portable air conditioners: Despite their claims, these machines barely got a room below sweltering, let alone the 78° F that’s widely 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.

“A portable air conditioner is an alternative—but not an ideal one,” says Chris Regan, who oversees Consumer Reports’ air-conditioner tests. Portable units are typically bigger, noisier, and more expensive, and use more energy. In fact, retailers report that many portable air conditioners are returned each season by dissatisfied customers.

How Portable Air Conditioners 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. It’s also a reason for the less-than-capable cooling: The portable unit uses 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.

How Portable?

And it’s debatable how portable they are, because once the hose is connected to the kit in the window, you won’t want to move the unit, which typically weighs 50 to 80 pounds—sometimes even more. 

More on ACs

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 Portable ACs

In our tests, we measure how long it takes a portable air conditioner to lower the temperature from 90° F to 75° F in a room appropriate for its claimed size. But few make it to even 80° F after 100 minutes. None makes our list of recommended air conditioners. But if you have no alternative, consider the Friedrich ZoneAir P12B, $580. While the unit earned only a Fair rating for cooling, it was a champ in our tests simulating brownout conditions, as were most of the other 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 fan. Create a cool breeze by running a ceiling fan or using a box fan.
Block the sun. Close the curtains and shades to keep the sun from overheating your room during the day.