8, 10, 12, Or 14,000 BTU Portable Air Conditioner?

"How much power do I need?" is probably the most basic question when evaluating portable air conditioners. I get many other questions, like "does it have to be vented outside?" (yes, or into the attic), and "what about drainage?" (many have auto-drain systems). But the most frequent and perhaps most important question regards sizing. It is not as easy a question to answer as it may seem.

All portable air conditioner manufacturers give a BTU rating for their units. But some are 'rounded up' to get an even number. Depending on the manufacturer, a 14,000 BTU portable air conditioner may actually put out only 13,500 BTU's. But an even more important factor is the heat load in the room. Large windows that let in sunlight, heat producing appliances like computers (or people!), ceiling height, door number and size, and presence or absence of central air all affect the work load for a portable air conditioner. Manufacturers generally recommend their units for rooms "up to... square feet". The maximum recommendations are based on optimal conditions, which in my experience rarely exist! So if a room is anywhere near the upper limit, I generally recommend upsizing. For units with heat, it is even more important because the heat function is usually not as powerful as the cooling.

There are potential downsides to upsizing. It costs a little more. For example, a 14.000 BTU portable air conditioner is usually about $50 to 100 more than a 12,000 BTU unit. Also, a unit that is too powerful may cool the room so fast that it won't run long enough to properly dehumidify the air. I have had not had this complaint. This would be more of an issue in an isolated room without central air or heat sources. A central unit should help keep the humidity at proper levels, even if the room is not quite cool enough. And if heat sources are present, the room likely won't stay cool for long while the unit is not running. My best advice? If you have questions, call me or someone like me, talk through these issues, and get the right unit for your needs.