You might be a renter, want to wheel your air conditioner around between rooms, or just simply don't have the cash for a fixed option. In any of these and more scenarios, a portable air conditioner is an option to consider, but because of their inefficiency it might be wise to know what you're in for if you get one.
Firstly, 'portable' in our language is slightly different to a manufacturer's idea of portable. While you can install these units without modification to the building, you wouldn't want to lug one from room to room the way you do with a fan. They're heavy (sometimes up to 40kg), not always easy to manoeuvre and require installation to your window using the supplied kit.
Portable air conditioners work basically the same way as built-in air conditioning: sucking in warm and humid air, cooling and dehumidifying it and blowing it back into the room. Single-duct models, with a duct connected to a window to vent heat from the room, can be very effective at cooling most of the room, but they draw the air from the room (in order to cool it) and vent some of it outside.
Venting the hot air outside through the duct results in a net air pressure reduction, so more warm air is drawn into the room from the rest of the house. The portable air conditioner thus faces a continual struggle to cool the room. Portable units are also noisier indoors than most split-systems (which have the advantage of having the noisiest component, the compressor, situated outside).
So while they are convenient and often comparatively cheaper than split-systems, single-duct portables are not as effective or efficient.
The heat extracted from the air is vented through an air duct that you install in an open window. The unit also condenses water from the air while cooling. Generally, this is collected in a tank or drained away in a tube. Many models will use the water to aid cooling, which can help with overall energy efficiency and reduce the need to empty or drain the water. Dryer air feels more comfortable and enhances the cooling effect. A venting kit is usually included so you can seal the gap around the duct to stop the cool air escaping.
Portable air conditioners are often noisy on high power; we've measured them at more than 67dB on full blast in some cases. That's louder than a normal conversaion (about 65dB).
New portable air conditioners entering the market must now display an energy rating label. Single-duct air conditioners have no stars as they are not energy efficient.
Portable air conditioners have historically been exempt from displaying an energy "star rating", but finally as of 1 April 2020, new portable air conditioners must meet minimum energy performance standards (MEPS) and display a new "zoned" energy rating label. This shows energy efficiency according to your location, as well as other things, including how noisy it is, its kWh use each year, and its cooling capacity.
Single-duct (one-hose) portable air conditioners such as the ones we test generally have no energy stars on their labels because, by their very nature, they aren't all that energy efficient at cooling a room down and are best for cooling or heating a person rather than a whole room. But the new labels offer some idea of how much energy they use over time, especially if you're in a humid region.
There is a transition period for existing stock to either run out or be registered with the regulators, so not all portable air conditioners will have this label.
Manufacturers don't recommend using an extension cord with your portable air conditioner. Typically, the manuals advise against it, and claim that doing so will void your warranty. Portable air cons are relatively power hungry, and your extension cord may not be able to cope, posing an overheating or fire risk. Consider the placement of the portable air conditioner in relation to the power socket. Some cords may be too short for your setup.
These are handy in much the same way that a television remote is handy (because we're lazy!), but with the added benefit of information on room temperature. You can also usually set automatic modes and timers to make life simple. An LCD display is handy so you can see the cooling status without having to get up and look at the screen.
Cool, heat (for reverse-cycle models), dry (dehumidify), automatic or fan only. Automatic or "smart" mode means they can be set for a target temperature and will switch to cooling mode (or heating for reverse-cycle models) as required.
These are useful to program the unit to turn on/off at certain times, for instance to cool the place down before you get home from work. Sleep timers are useful at night as they switch the unit off after a set period rather than running all night, and usually have automatic temperature adjustment. This adjusts the temperature to a comfortable level for sleeping in,so the air conditioner doesn't work as hard (and also more quietly) when you're sleeping.
Louvres to direct airflow
Most have manually adjustable louvres, though a few have only fixed louvres. Other models have automatically oscillating louvres, which enable the cool air to be directed more widely rather than just in a fixed direction.
These come with filler panels to close the gap in an open window and direct hot air outside using an exhaust hose.
These units can be quite loud and distracting to run, especially if they are on full blast. They can compete with normal conversation, and can be distracting if you're watching TV or listening to music.
Portable air conditioners will have a collection tank for water; many new models use the water to aid cooling which reduces the need to empty water from the tank.
Ease of use
If you will be moving the portable air conditioner from room to room, look for easy to access handles and good clearance between the floor and the bottom of the unit. Smaller wheels on pile carpet can be a nuisance.
Some newer models let you control the appliance through an app or even smart speaker. These features may be useful if you need to turn the unit on or off when you aren't home, but the standard remote control that comes with most models will usually do the job.
Portable air conditioners we tested most recently ranged in price from $349 to $1395. As with all appliances, a higher price tag doesn't always guarantee better performance. Of course, they also cost money to run, and we take energy efficiency and performance into account in our portable air conditioner reviews.