How To Determine AC Tonnage From Model Number

When choosing an air conditioning unit for your home, it is important to choose the right size.

You may want to learn about how to determine the correct size of unit for your home. 

What is AC Tonnage?

Tonnage refers to the cooling capacity of an air conditioning unit. Tonnage is measured in BTUs or British Thermal Units.

For reference, one BTU is the amount of energy required to heat one pound of energy by 1 degree Fahrenheit at sea level.

This may sound complicated, but the tonnage of an air conditioner will help you determine the size of air conditioner you need, based on your home’s size. 

How to Find AC Tonnage

Most of the time, you will not find the AC tonnage on your air conditioning unit. You will need to do a bit of math to figure out the AC tonnage.

The power of your AC unit will likely be listed in BTUs. You will need to take the number of BTUs listed on your unit and divide it by 12,000 to determine the AC tonnage.

For example, if your air conditioning unit lists 48,000 BTUs, divide that by 12,000, and you get 4. This means that you have a 4-ton air conditioning unit. 

Why is AC Tonnage Important?

The AC tonnage is important because it will help you determine which size of air conditioning unit you will need for your home

A good general rule is that one ton will be able to cool 400 sq feet of space. So, if you only want to cool an 800 sq ft apartment, you can go with an air conditioning unit with a 2-ton unit. 

To pick a good air conditioning unit, you will have to know how many sq feet you are looking to cool. Air conditioners are not one size fits all and may differ drastically depending on the size of the home. 

Why is the Size of the AC Unit so Important?

If you get an oversized unit or too small for your space, it just won’t function properly. A unit that is too small will cool the space too quickly and will turn itself off after a short period of time.

This may lead to the unit functioning improperly and might result in you having a humid home because the unit does not run long enough to remove humidity. 

If your air conditioning unit is too small, it will have to run full blast all the time to cool down your space. This will result in you paying a lot of money to keep your house cool. 

If your system is too small, it will likely lead to you paying for frequent repairs. If the unit is running at full capacity all the time, it will likely not have a very long lifespan and will wear out quickly.

Likewise, if the unit is too large, it will not have to work as hard but will turn itself off and on often. The unit requires a lot of energy to start back up after shutting off and will likely burn out quickly. 

When the air conditioning unit is the right size for space, it will run efficiently. As long as the machine runs efficiently, it shouldn’t put too much stress on your wallet. 

Factors that Affect AC Sizing

Many factors will affect which size of air conditioning unit you need. The first and most obvious factor is the size of the house, but there are many other factors as well.

House Size

As mentioned throughout this post, house size is a big factor when choosing an AC unit. Having a unit that is too large or too small will affect the lifespan of the unit, the efficiency, and the overall performance.

You will need to know the square footage of your home when setting out to buy an air conditioning unit, and it is usually best to work with a professional to find the best option for you.

The style of your house and the number of floors will also impact the unit’s size that you will need.


The location of your home is also a factor in determining the size of your AC unit. Homes in cooler, drier climates will not need units as large as homes in hot or humid climates.

Your home’s orientation on your property may also impact the size of the AC unit. For example, if your home gets a lot of shade from trees on the property, you may require a smaller unit than if your home gets full sun all day. 

Number of Windows

Windows make for beautiful views but, in most cases, lead to energy loss, which requires more cooling power. 

The window type may also make a big difference, depending on whether the windows are single-pane, double-pane, triple-pane, or specifically energy-efficient windows.

Existing Insulation

The insulation in your home will also play a big role in helping to keep your house cool during a summer day.

In most places, if your house is newer, it will be built up to a specific code, and the insulation shouldn’t be an issue. But many older homes were built before such building codes were put into practice and may have inadequate insulation, making them more expensive to cool and heat. 

Final Thoughts

It is important to understand the size of the air conditioning unit you will need for your home. Even if you plan to work with a professional, you will want to understand all the ins and outs related to your air conditioning unit as it can be a large investment that will serve you for many years.

Many factors will influence the size of the unit you’ll need, so it is best to work with a professional who will support you with finding the exact suitable unit that will work perfectly for you!