First, there are really two kinds of air conditioners that most people can buy and install themselves. Window units, and portable units. Others, like full HVAC systems or the AC’s installed directly into the wall itself, will require the work of a contractor—though some of the tips below can apply to them as well.
For most people, a window unit will be the ideal kind of air conditioner to buy. It’s cheap, easy to find, and does the job well enough. But it isn’t for everyone. It’s heavy, allows in more road noise and summer air, and has to be set into the window at an angle, so it can properly drain condensation on a hot day.
If the window is too narrow, or you live in an area with either exceptionally bad air quality (like on the highway or near a feedlot) or terrific amounts of outside noise then you can get a portable AC unit. They typically are the size of a mini-fridge and you roll them out when needed. Instead of taking up the entire window they only take up about 6-inches, so less bad air or loud noises come in. A large hose is attached to the AC and you install it in the window to exhaust all the hot air the air conditioner produces. However, the exhaust system isn’t perfect and thus portable ACs don’t cool quite as effectively as a window unit—they’re also more expensive and are typically have a built-in reservoir that collects condensation and must be emptied by you.
Now that you have a basic idea of the kind of air conditioners available let’s talk about how to choose the right one for you.
Step One: Measure the window and the room
The first thing you want to do is know the size of the window you’ll be installing the AC into. The more powerful an AC the larger it is, so you can’t hope to fit a huge AC in a tiny window.
Next measure the space that you plan to cool. I like to measure each room separately. You’ll want to note how long and wide the room is, as well as how tall the ceilings are.
At this point, if you’re planning to kit out your entire living space with ACs, you should have a little list of each room’s dimensions. Go ahead and note the kitchen, it will have a stove which means it gets hotter and will need a more powerful AC.
Also, note any rooms that get a lot of sun during the day. These rooms will also get a lot hotter and you’ll want to factor that in.
Step Two: Calculate
This is it, the worst part of choosing an AC. The power of an air conditioner is determined by the number of BTUs (British Thermal Units) it outputs. A small bedroom (think 10 feet by 10 feet with an 8-foot ceiling) will be fine with a sub-5,000 BTU AC. Double the size of the room and you should double the number of BTUs needed.
If you’re like me and don’t want to track down a chart that shows how many BTUs are needed for certain square footage, then a BTU calculator is your new best friend. I like this one, but they’re all doing the same thing: taking all those measurements and notes we recorded in step one and turning them into the number of BTUs you need.