What You Need to Know about Portable Air Conditioning
Public opinion seems pretty united: portable air conditioning just doesn't work as well or as efficiently as central air conditioning or even a window mounted unit. However, there are some situations where neither of the two more preferable alternatives is possible. If you live in a small apartment, for example, and the windows are either inconveniently located or the landlord won't permit installation of a window unit air conditioner, then portable air conditioning is your only viable comfort option. You may also need occasional cooling for a garage, workshop, or other small space where installation of a permanent unit is impractical. Here again, portable air conditioning can be a viable way to achieve a workable comfort level without the hassle of permanent installation.
Portable air conditioning units work on the same principle as other air conditioning, in that it pulls in air, dehumidifies and chills it, and pushes it back into the room. Unlike other systems, however, portable air conditioners use only air that is already in the room, rather than pulling it from outside. This is one of the reasons they are inherently less efficient. In fact, the majority of user complaints about portable air conditioners involve the fact that they don't get the room as cool as window units or central units. For that reason, you should probably not expect the level of cooling with a portable unit that you're otherwise accustomed to. On the other hand, portable units can "take the edge off" a hot room, providing some level of comfort in situations where more standard solutions aren't workable. It's also important to make sure the unit has enough cooling power for the room where it is being used. If the room is 150 square feet or smaller, a 7,500 BTU unit should be adequate. For 200 square feet, 9,000 BTU units are more appropriate. In other words, you should plan on adding 1,000 to 1,500 BTUs of capacity for every 50 square feet you are trying to cool.
Dealing with Condensate
Because portable air conditioners aren't mounted in a window or outside, and because they work by pulling moisture out of the air, you'll need to anticipate emptying the resulting condensed moisture. Some models have a tray that must be removed (or, in some cases, the whole unit has to be upended) in order to empty the water. Others have an exhaust hose that can be passed out a window (these models usually also include a foam insulation kit to permit better sealing of the window) to drain the water outside.