A window air conditioner is a serious investment, both of your money and your time. You may be asking yourself, “what BTU capacity do I need?” – or, even more likely – “What even is BTU?” Fortunately, we’re here to make your search for a new air conditioner as breezy as possible (yes, pun intended).

Skip the reading and take our quiz to find the perfect window A/C size for your home (it’s easier than your standard BTU calculator). Or, continue below to learn more about the factors to consider when choosing what size window A/C to put in your room.

Learn more about the different factors you should take into account for helping you choose the optimal capacity window A/C.

First off, what are BTUs?
When it comes to air conditioners, this is the most important term to know. BTUs, or “British thermal units,” determine cooling power. In a typical BTU to square footage calculation, one square foot of floor space requires at least 20 BTUs. However, what most brands and retailers don’t tell you is that it’s a safer bet to buy an A/C with a capacity of 23 or 24 BTUs per square foot – because there are some other factors that you need to consider beyond square footage.

Floor area
The bigger your living room or bedroom, the more BTU power you’ll need in a window A/C. The smaller your room’s floor area, the less you’ll need to cool the space down. As a general rule, go with 6000 BTUs for a space that’s 250 square feet, and 8000 BTUs for a space with 350 square feet. July has units in these sizes that are beautiful, energy-efficient, and WiFi-enabled – click here to learn more.

If you believe a unit with stronger cooling power might be necessary, use this chart to help you decide.

Ceiling height
People who only measure their floor area and nothing else could still purchase the wrong window A/C. That’s because a space requires extra cooling power when the ceiling is higher than eight feet. For example, our Small July A/C model has 6000 BTUs and is good for rooms up to 250 square feet. Depending on your room’s ceiling height, you might want our Medium July air conditioner instead. That one has 8000 BTUs.

People in your home
The more people you live with, the more BTUs you should consider. Say your living room is average-sized and three people are regularly in there together. In that case, you’re A/C should be able to handle at least 6600 BTUs. With four people, bump that number up to 7200 BTUs. Usually, cooling power comes in gradations of 1000 BTUs. So, if you do live with more than one other person, we’d recommend July’s 8000 BTU option.

Sunlight
Unless you’re a scientist who can measure the intensity of sunlight, it’ll be hard to get an exact calculation here. Instead, think of it this way: How quickly does your bedroom or living room heat up when you leave the blinds drawn? If your answer is “pretty quick,” increase the BTUs you're looking for by 10%.

 After looking over these factors, chances are you’ll need more cooling power than you first thought. That means you could end up draining a ton of energy. But you can avoid this with a July air conditioner. With our smart phone app, you can schedule how long to have the air conditioner running. Or you can shut it off away from home, since all of July’s models are WiFi-enabled. Not to mention, they produce 2/3 less carbon emissions than the average window A/C. Learn more about if the July window A/C is right for your space.