The Secret Term to Know When Shopping for Your Air Conditioner

Shopping for a new AC unit? Learn why British Thermal Units matter.

Sean Jackson
Sean Jackson is a creative copywriter living in Florida. He's had work published with Realtor.com, theScore, ESPN, and the San Francisco Chronicle. In his free time, Sean likes to play drums, fail miserably at improv and spend time at the beach.
Sean Jackson
3 min read

More BTUs aren't necessarily better, depending on the size of the space you're trying to cool.

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It's time to start gearing up for another scorching summer. If you thought last year was hotter than normal, then you would be right. We faced our hottest year on record in 2023. Meteorologists predict this summer will be even hotter, with much of the US expecting to see above normal temperatures. Residents in southeastern states and parts of Texas could be facing their first major heat wave as early as this weekend.

When shopping for an air conditioner, one term you will come across is BTUs, otherwise known as British Thermal Units. This guide will help you understand what a BTU rating is and how it factors into choosing the right air conditioner for your home. For the purposes of this post, we're focusing specifically on BTU ratings for window air conditioners

Read more: 5 Signs You Need to Replace Your Window Air Conditioner

BTU basics

A measure of an air conditioner's power is its BTU rating. BTUs are the energy used to remove heat from a room. Therefore, the more BTUs an air conditioner unit has, the better equipped it is to cool a larger space. 

How many BTUs do I need?

When determining the BTUs you need, measure the room dimensions where you want to install it. Once you calculate the square footage, you'll need 20 BTUs for every one square foot of room space. Along with room size, you should also factor in ceiling height, whether the room receives shade and window sizes (if applicable). 

Next, multiply the square footage of your room by 20. If your space is 300 square feet, you want to find a model capable of producing at least 6,000 BTUs. As a guide, consider 5,000-BTU models for rooms 150 square feet or smaller, 8,000 BTUs for medium-size rooms (340 square feet), and 12,000 to 14,000-BTU models for rooms with square footage from 550 to 800.

Having the correct power is imperative. It allows the unit to operate at maximum efficiency, which will save you money and prolong the life of the air conditioner. 

Avoid these common AC errors

If you try to use an air conditioner with too few BTUs, your air conditioner will turn on and off more often while trying to keep up, which could result in higher energy bills.

Running it all the time also forces undue pressure on your air conditioner, potentially requiring more maintenance and shortening it's lifespan.

You also don't want to buy a model that's too powerful for a room. Sure, a 12,000-BTU air conditioner will cool a small space (150 square feet or less) quickly. But it might cool it too quickly, preventing it from removing some of the ambient humidity from the room and leaving the room damp.

Two final things to know

When shopping for air conditioners, look for models that have eco-settings. Eco-settings can help your unit operate more efficiently, allowing you to better balance comfort with savings.

Placement of your air conditioner is also important. You want to refrain from placing your unit next to a television or other appliance where it can detect heat, prompting the air conditioner to continually run. 

Read more: Going On Vacation This Summer? Here's How to Cut Down on AC Costs While You're Away