Buying an air conditioner is hard. There are lots of specs that aren’t found on any other kind of product, the damn things are heavy, so if you buy the wrong one you’ll dread returning it even more, and if you mess up you will find yourself living in an unpleasant ice box, or a muggy misery. But don’t worry, it’s actually fairly easy to buy, install, and enjoy an air conditioner.
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.
Step Three: Figure Out How Many Air Conditioners You Need
Okay, you’ve done your measurements, plugged them into the calculator, and know how many BTUs you need. You might assume this is where you just head to Lowes and choose the cheapest AC with the required number of BTUs.
Don’t do that! Instead, you first need to consider how many air conditioners you actually need. This is where a lot of people mess up and find themselves with rooms that are either way too muggy or way too cold.
The problem is the air flow of the home. If you live in a railroad apartment and you put the giant AC in the kitchen, then your big bedroom at the other end of the space is probably going to be way too hot on most days. The air warms as it moves through a home and if the air flow in the home isn’t good, then the cool air will simply never reach parts of the house that need cooling. That leaves you with hot spots. The cool muggy spots come on when an AC is too powerful for the space where it’s installed. If the airflow in the kitchen is terrible, then you’ll have a hot house and a really gross kitchen.
If you have a lot of hallways or tall narrow rooms, then consider multiple air conditioners and adjust your calculations. So a 12,000 BTU unit for the bedroom and living room that are right next to each other, and a 7,000 BTU unit for the small kitchen with terrible ventilation.
Also, consider how often rooms need to be cooled. It’s okay to close a door off to a little used seating room. Or just close the kitchen when you’re not cooking and leave it completely un-airconditioned.
Step Four: Buy that AC
Now that you know how many air conditioners you need and the BTUs that are necessary for each one, you’re ready to go buy an AC. Everyone has a different budget and different requirements and that will factor into which one you get.
A low profile AC is great if you have limited windows in a room and want to allow in more sunlight—but it’s also more expensive. Some air conditioners are better insulated for sound so they’re much quieter. That can be great for a room where you watch a lot of TV or sleep but, as with the low-profile ACs, they’re costly too.
“Smart” air conditioners are still a rarity and charge a premium. However, most air conditioners past the 6,000 BTU range will be programmable, so you can set them to turn off for parts of the day you’re not home, or only run when the AC unit’s internal thermostat records a certain temperature. They’re basically smart ACs but you just can’t set them with your phone.
As for brands I’ve found Frigidaire to be reliable, easy to find, and with nice and easy to read controls. Haier, a Chinese company, and LG, a Korean company, have both made significant inroads in the US and produce really excellent and affordable ACs as well, however they are typically harder to find in brick-and-mortar stores.
Step Five: Install That AC
Here is another place people run into issues. Installing an AC is actually pretty easy, but it requires brute strength and a little patience. Try to make sure you have a second person on hand to help, and even more if you’re installing an AC in a multi-story building. You want the unit secure so it doesn’t fall out.
If you’re in an apartment, it’s a good idea to reach out to a super, landlord, or property management personnel for help. They can install outside supports for larger ACs and they’ve probably done enough to make sure the job gets done safely.
If you’re on the first floor, or in a residential home then unbox that bad boy and grunt and groan your way to the window with it. You want to set the AC in the window at an angle for drainage. That angle should always be away from the inside of the house. Never install an AC so that it is perfectly level. If the condensation has nowhere to go it will linger in the unit itself, breed mold, and then leave you with an AC that spews out cold air that smells like garbage.
Some people like to use bricks to create the tilt, but a small piece of wood cut to the same length as the window opening can be great too. And if the AC is really large and doesn’t have enough base within the window frame to rest on then you can buy a support and install it on the outside of the home. But this is usually only necessary for really large air conditioners. Slide the window close and make sure the AC is secured in the window.
Now grab a piece of insulation board. This is the trick I learned after growing up in a 100-year-old farmhouse in a town that would have months of 100-degree weather and it will separate your nice cool home from your friend’s sad and hot one.
Typically, people just pull open those accordion shutters on either side of the AC, bolt them to the sides of the window frame and call it a day. But these shutters are terrible. They have gaps that leak air and let in bugs and sound. If you have the money you can build a custom frame for your air conditioner, but the insulation board trick will cost significantly less and be done in ten minutes.
Insulation board can usually be found in 8- to 10-foot sheets at any home improvement store and it shouldn’t cost more than a few dollars. Measure the gaps between the window and the AC and cut out that amount of insulation board. You can then wedge it into the gap and call it a day, but I usually grab some fabric that compliments the room and wrap the board in that so I don’t have to stare at ugly silver insulation board all summer. Not only will it keep stuff out and help insulate the room, but it will muffle noise from outside too.
Finally, check for any other gaps around the AC and close off with a piece of smaller insulation foam. Beyond that, you can put up window treatments to cut down the amount of sun coming into rooms at the height of the day. The sun will make things hotter and force the AC to work harder, which can get expensive. So good shades or even some white curtains will help and save you money in the long run.