Keeping Cool With a Portable Air Conditioning Unit

Let's face it, window air conditioners are often unsightly, use up much of your window space, and are too heavy and awkward to move from room to room more than once or twice a season.

If you want to keep a room cool in the summer, and want the flexibility of moving the air conditioner to a different room as the need arises, a portable air conditioner is the way to go.

If you live in a dry climate, consider an evaporative portable air conditioner. These units draw outside air into the unit (through a hose attached to a small slot that you put in a window), and blow it over water that comes from the evaporator tank (you have to fill it every couple of days or so). The evaporation of the water cools down the air in the room, and helps you not feel so parched, as well. Evaporative portable air conditioners are very inexpensive to operate because they are so efficient.

If you live in a less dry climate - average or above average humidity - an evaporative air conditioner will just make you miserable, since humidity is a big part of why it feels so hot. So you'll want a condenser-based portable air conditioner, which works like most window air conditioners, with a compressor, a refrigerant fluid, and condenser coils, and which draws moisture out of the room rather than introducing extra moisture. Condenser-based portable air conditioners have two hoses that connect to a window vent to the outside; one draws in air from the outside, and the other exhausts that same air out, along with some of the heat and humidity from the room.

Condenser-based portable air conditioners don't always vent the humidity to the outside; some store it in a basin inside the unit, and you have to remember to empty it every day or so, or the unit shuts off. Some units are hybrid units with both a basin and the evaporation feature, and they'll evaporate the condensed water to the outside when the basin becomes full, but they operate less efficiently when they have to evaporate the water, since the evaporation uses up extra energy.

Portable air conditioners do not have ENERGY STAR ratings so it is hard to know whether you are getting an efficient one. Make sure you buy the most efficient unit you can find for the BTU output you need. Don't buy an over-capacity unit (don't buy a 12,000 BTU unit to cool a single, closed room) because you'll just make the unit cycle on and off very frequently, which means it will be much less efficient than it would normally be, and you may damage the unit.

Some portable air conditioners are actually combined air conditioner / heat pump units, which means that you can use them to heat a room during cooler weather (but not really cold weather, as they will be less efficient than a regular electric heater). I'd recommend these units if you want an inexpensive source of heat in the shoulder season, or in warm areas where winters are very mild (e.g. Florida, South Carolina).

Look for an EER rating of about 10.7 for any portable air conditioner under 20,000 BTU. For heat pump units you can actually find higher EER ratings of up to 14.4 so a combined portable air conditioner and heat pump may be the best way to keep your rooms cool in summer, as well as stay toasty warm when the thermometer dips.