What Size Air Conditioner Do I Need for My Home?

What Size Air Conditioner Do I Need for My Home?

When it comes to air conditioners, there are many choices available. It’s nice to have so many options, but how do you know which size to get? This detailed guide will go over some important terms and concepts so that you can more confidently select an air conditioner that will be ideal for your home.

Before we begin, we have to note that when we talk about “size” in relation to an air conditioner, we’re not talking about its physical size. Yes, more powerful ACs are typically larger than not-so-powerful ones, but what we’re really talking about is how much cooling power an air conditioner has. To put it another way, “size” can refer to the size of the area you’d like to keep cool.


If you haven’t already come across the term “BTUs,” chances are you will soon. Practically every air conditioner in the market is described by using BTUs, so it goes without saying that it’s a term that you should learn more about.

BTUs are thermal units of energy. To be specific, BTU stands for British thermal unit. Basically, it indicates how much heat something can either add or remove from an area. BTUs are used with stoves and grilles; stronger appliances that can burn hotter have more BTUs. In the world of air conditioners, BTUs refers to how much heat can be removed from a room or home in an hour. A unit with more BTUs would be able to cool a larger area, while a unit with fewer BTUs would be better suited for a small space.

There’s a whole science behind the idea of BTUs. In Britain a few hundred years ago, it was determined that one BTU is how much energy was needed to raise the temperature of one pound of water by one degree Fahrenheit. (If you’re into science, keep in mind that the water has to be at sea level due to the changes in pressure that result from changes in elevation.)

One BTU, if you think about it, is a very little amount. When we discuss air conditioners, we’re referring to cooling units that could have tens of thousands of BTUs.


Instead of dealing with such high numbers of BTUs all the time, we often use “tons” to describe air conditioners. A one-ton air conditioner has the equivalent of 11,917 BTUs. We round that number up to 12,000. A 2-ton AC would have roughly 24,000 BTUs, a three-ton AC would have 36,000 BTUs, and so on. There are 2.5-ton and 3.5-ton ACs, and five tons is typically the limit to residential air conditioners.

Are you curious as to why the industry uses tons? Well, in many areas, ice was traditionally used to cool buildings before the advent of modern technology. The ice would absorb heat from the air in the building, and obviously, it would slowly melt when doing so. Scientists were able to quantify how much heat the ice could absorb. It was determined that 1 ton of ice would melt in a 24-hour period by absorbing 286,008 BTUs: 286,008 divided by 24 hours results in 11,917 BTUs per hour. We don’t use ice anymore to keep our buildings cool, thankfully, but we have hung onto the terminology of using tons.

How Many BTUs or Tons Do I Need?

Now, we can move on to discussing how many BTUs your home might need. The biggest factor is the size of your home. To start, let’s use the idea that 20 BTUs are required to cool one square foot of space in a building. If you’re cooling an area that’s 100 or 1,000 square feet, you’d need 2,000 or 20,000 BTUs, respectively. You can do the math to determine that a 500-square-foot space would need 10,000 BTUs, a 750-square-foot area would need 15,000 BTUs, and so on.

When we get into the higher numbers, that’s when we switch to tons. Whole-house air conditioners are generally categorized by how many tons they are. A 1,500-square-foot home would require an AC with 30,000 BTUs, and this translates into 2.5-ton unit. A 3,000-square-foot home has a lot of space to cool, and it would likely need a five-ton unit. Sometimes, there may be different zones in the home. You’d first figure out how many square feet are in each zone and then determine what size of AC would be needed.

Other Factors

While the guidelines that we just presented are great to give you an idea of what size of an AC would work, there are several other things that should be considered.

All of the following factors can affect how big or small of an AC you might get:

  • Whether your home has an open or closed layout
  • How much shade is on your home
  • How much insulation your home has
  • How tall your ceilings are
  • How many floors there are

If you have extremely tall ceilings, then you’d have a lot more cubic feet of air to cool. For those of you who have newly built homes, it’s likely that you have very good insulation to keep your home cool in the summer. If you have mature trees providing shade for your home, not as much sun would shine in through your windows. The climate of the region plays a major role as well. As many of us know all too well, our area of Alabama can get extremely hot and humid in the summer. We have to take that into account. Homes in our area are going to require more BTUs to keep and stay cool than homes somewhere up north. If you don’t get an AC that has enough power, it will struggle to keep things cool and could need to continually run, and it could wear down prematurely.

As you can see, there can be a lot that goes into calculating the ideal number of BTUs. Many people leave it up to a professional so they can be sure that they’re getting the right size of the unit. If you live in Theodore or any of the surrounding towns, Hansen Air Pros can assist you with your air conditioner installation.

Here to Help

You can trust us to get the job done correctly for you. Hansen Air Pros was founded in 2006, and we’ve worked hard to grow our business and serve our local community. We have highly trained technicians who are always respectful and professional, and whenever you have a question, we’ll be ready to provide you with the information you’re looking for. We have up-front pricing, financing upon approved credit, and no hidden fees. When you work with us, we’ll strive to keep you satisfied with all aspects of our service. In addition to AC installation, we offer assistance related to generators, indoor air quality, heater installation, and repairs and maintenance related to air conditioners and heating units. Call us if you’d like to discuss your upcoming AC installation or to set up an initial consultation.