How many BTUs per square foot? What size AC do you need for your home? Here's everything you need to know to get a just-right air conditioner to keep you cool.

By Lisa Milbrand
July 20, 2021
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With massive heat waves hitting the country this summer—even in places that are known for staying cool—it's no wonder more and more people are in the market for air conditioners right now.

But choosing the right size window AC unit or central air conditioner for your room or whole home isn't just a matter of more is better. In fact, getting an air conditioner that's too large for your house could create just as many problems as one that's too small. If the air conditioner is too big, it could lead to your unit cycling on and off too often, which reduces its ability to remove humidity from your air, increases your electric bills, and can lead to hotspots and uneven cooling in your home.

Here's how to decide if you're getting the right size air conditioner to help you stay cool this summer.

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Measure the Area You'd Like to Cover

Before you determine how many BTUs of air conditioning you need, you need to figure out your square footage by multiplying the width by the length for simple square or rectangular rooms. 

Determine How Many BTUs You Need per Square Foot

Energy Star expects you to need between 20 to 30 BTUs per square foot of cooling power. So a room that's 250 to 300 square feet would need 7,000 BTUs to cool, while a room or home that's 1,400 to 1,500 square feet would need 24,000 BTUs.

RELATED: The 9 Best Portable Air Conditioners to Use This Summer

Take Room Traits Into Account

According to Energy Star,  you'll need 10 percent less cooling capacity if the room is shaded—and 10 percent more if it gets a lot of sun. Add 600 BTUs for every person beyond two who regularly occupies the room, and an additional 4,000 BTUs if you're cooling the kitchen, to account for all the heat from your stove and other appliances.

Other factors that could impact how many BTUs per square foot you need include things like how much insulation you have, how many windows are in the room, and even if you have high ceilings. 

Decide What Type of Air Conditioner You Need

You have several different AC options to help you keep your cool.

Central air conditioners cover your whole house with a single unit, allowing you to stay cool in every room of your house. But they can be more expensive to install, especially if you're trying to retrofit them into a home.

Window AC units are easier for a DIYer to install, but only cool one room off at a time—and require access to a window.

Portable air conditioners allow you to move the cooling capabilities from room to room, and some models don't require venting to the outside.

RELATED: The 11 Best Window Air Conditioners to Cool Your Home This Summer, According to Reviews