Do you have a window? As we've noted in each section of this report, you MUST have a window to use a portable air conditioners as they need to be able to vent hot air outside to deliver cool air inside. We saw many low ratings from unhappy buyers who did not realize this, and it tends to bring down the overall rating for these units for something that isn't the AC's fault. Portable air conditioners come with a window kit, which uses a few inches of window space for a vent hose or hoses. Installing these kits is usually straightforward, but some instructions require you to screw the mounts into the sill and sash, or to use duct tape to hold it in place and seal against leaks. Complaints about difficult-to-install window vent kits and unclear assembly instructions sometimes crop up in user reviews of many otherwise well-liked portable air conditioners.
How big a portable air conditioner do you need? Select the size of your portable air conditioner based on the square footage and setting of your space. The ideal size has enough power to effectively cool your room while running long enough to remove as much moisture from the air as possible. Because of the challenges all portable AC units have in cooling a room compared to window models, expect cooling to be notably lower than a like-sized window air conditioner -- delivering only 60 percent of the cooling according to testing by ConsumerReports.org. As a guideline, expect a 10,000 BTU portable AC to be adequate for rooms up to 300 square feet, a 12,000 BTU portable air conditioner to be suitable for spaces up to 400 feet or so, and 14,000 BTU models to be right-sized for rooms of around 500 square feet. Keep in mind that because standards for portable air conditioners are looser than those for other types of air conditioners, like-sized models from different makers may deliver a little more or less cooling than that. Rooms bigger than 500 square feet will present a challenge for even the largest consumer portable ACs. Portable air conditioners rated lower than 10,000 BTU are available, but are only suitable for very small rooms. We found a terrific guide to portable air conditioners on the Sylvane.com website that extensively covers how to choose the right size unit, as well as challenging installation scenarios, such as with a sliding glass door.
Will you need to empty the water tank? Air conditioners pull extra moisture out of the air -- reducing your room's humidity and making it more comfortable. The best units use a self-evaporative system to automatically disperse this moisture out of the vent hose under typical conditions. For units without this system, or in areas or on days that are excessively humid, users have to manually drain the water tank or install a drain hose.
Filtering the air. Most portable air conditioners include one or two built-in air filters. For maximum filtration, look for a unit that has a washable pre-filter and an additional carbon filter, which can remove finer particles such as mold, pollen and dust. Some dehumidifiers have ionization features to better trap particles.
Check your outlets. Most portable air conditioners use standard 115-volt AC, but they can draw a lot of current. Make sure the outlet is on a circuit that can handle the load and don't add to the strain by connecting too many other electrical devices to the same line. Experts generally advise against using an extension cord but if one is a must, use a high-quality, heavy-duty appliance cord rated to handle the current draw of your portable AC.