Portable Air Conditioners: What To Look For

Portable units don't compare well to window air conditioners

As a group, portable air conditioning units do not receive the best reviews from owners. The main complaint is that they don't cool as well as window air conditioners. This is an assertion we saw repeated almost everywhere -- that portable air conditioners do a good job of taking the edge off a hot room, but experts say they don't chill a room like a window unit can. Most owners say the best application for a portable air conditioner is for those who need to reduce the temperature enough to sleep and be moderately comfortable -- but a portable cooling unit won't be able to make a room truly cold. Portable air conditioners are also fairly fussy, because they need to exhaust air to the outside and usually need to be drained of water taken from the air in the cooling process.

How portable air conditioners work

Most portable air conditioners cool and dehumidify a room, and many can also be used as fans. Some can be used as dehumidifiers separately from the cooling function. Still other portable air conditioners can also be used as space heaters. Though portable air conditioners are convenient and offer more than portable cooling, the main disadvantages are that they are more expensive and don't work as well overall as window air conditioners.

Portable air conditioners, though easier to install than window units, are not quite as mobile and trouble-free as you might hope. You'll need to place the unit somewhat close to a window, because you'll need to exhaust hot air outside. Portable AC units come with an exhaust tube and plastic or foam insert for your window. Because all air conditioners also dehumidify the air, you'll either drain water in a bucket or out a window with a drainage hose. Lastly, though portable air conditioners can be wheeled from room to room, they are heavy (50 to 90 pounds on average) and bulky; most portable cooling units have a 12-inch to 18-inch footprint and are about 30 inches tall.

A high energy efficiency ratio (EER) means that the portable AC unit will cost less to run in the long term. However, columnist James Dulley reports that EER isn't measured the same way for portable air conditioners as it is for other types: "There are no formal standards for these tests, as there is with window air conditioners, so the EERs can actually vary depending on many factors." Still, EER ratings are helpful when viewed in relation to other portable air conditioners, even if the ratings are taken only as a general indication of efficiency.

Like window air conditioners, portable AC units draw in the surrounding air and cool it, discharging heat outside. The portable air cooler dehumidifies the air and the collected water is called the condensate. The condensate is removed from the air conditioner using two main methods. In the first, a bucket or tray inside the unit collects water, which must be manually emptied frequently. The second method evaporates the water and exhausts it through the main venting hose. Portable air conditioners must also vent the resulting hot air through an exhaust hose that extends outside a window, door or air vent.

Room size and Btu

Although you can buy a smaller 6,000- to 8,000-Btu (Btu is a measure of cooling power) window unit for less than $175, portable air conditioners don't get much cheaper than about $300. We find it odd that smaller 7,000-Btu units like the Edgestar Koldfront PAC8000S (*Est. $290) sell for almost the same price as much larger 10,000- and 12,000-Btu window air conditioners, which will cool a larger area. Although the smallest portable air conditioners aren't much of a deal over small window units, prices for larger models are more comparable. Keep in mind, however, that you'll need more Btu if you go with a portable air conditioner than you would for a window unit in the same room. For a 300-square-foot room, you should look for about an 8,000-Btu window unit, but you'd need a 10,000-Btu portable air conditioner.

When estimating, err on the high side for particularly sunny rooms, or if you live in an unusually hot climate. Keep in mind, however, that bigger is not necessarily better. An oversized air conditioner will not dehumidify the air as effectively, so the room may become cool and damp. The chart below offers a rough estimate of the number of Btu needed for your room size, though the manufacturer's rating may be higher. Owner reviews are consistent with this chart, and we read many comments indicating that the (higher) manufacturer's rating can be inaccurate.

Important Features

Here's what expert reviews say to look for in a portable air conditioner:

• Match Btu to room size. Keep in mind that you need more Btu in a portable air conditioner than you would in a window unit for the same size room. You may need to increase the Btu rating by up to 50 percent if you live in a hot climate or need to cool a room with heat-generating appliances or electronic equipment.

• Look for a model with casters or wheels and handles for easier transport. But don't plan on frequently moving a portable air conditioner from room to room, because all are quite heavy and require the window kit to be installed.

• Look for a portable air conditioner with oscillating louvers or multidirectional airflow, because this will circulate the air and cool the room faster. This is especially important because portable air conditioners don't produce as much air volume as window units. Combining a ceiling or box fan with an air conditioner can also help with even cooling.

• In reviews, experts prefer digital controls, which allow you to set the temperature and control the timer. However, keep in mind that digital controls are more prone to failure than manual controls, and most portable air conditioners have 90-day warranties.

• Be certain that your unit has a venting or exhaust hose and a window adapter kit. If you don't want to empty water buckets, look for an optional water-drainage hose or a system that exhausts water outside.

• Duct tape is your friend. Users report that duct tape can be particularly helpful for sealing gaps during the installation of the exhaust hose. Weather stripping around the edge of the window kit can also help keep cold air inside and hot air out.

In general, portable air conditioners are not as effective as window air conditioners. If your only option is a portable AC unit, look for a model with a high enough Btu rating for the size of your room. Going with a larger unit than you think you need is recommended if your room gets a lot of direct sunlight or contains heat-producing electronics and appliances.