AC Tonnage: There's Tons to Learn About Your Air Conditioner's Cooling Capacity

by Shelley Frost
graph showing the relationship between square footage and ac tonnage

Are you in the market for a new AC unit? There's a ton to think about, including tonnage.

Read More Heating and Cooling Articles

When you hear the word "ton," you probably think of a weight measurement. But when it comes to an air conditioner, tonnage doesn't have anything to do with how much the equipment weighs. It's an important measurement that helps you choose an AC system that can handle your cooling needs.

What Is a Ton in Terms of Central Air Conditioners?

A ton is a measurement that describes the cooling capacity of the central air conditioner. It describes how powerful the system is and how well it can cool the space based on how much heat it removes. You can think of each ton as a cooling power unit, with a higher tonnage having more cooling power.

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What Does Tonnage Measure?

Air conditioner tonnage measures the amount of heat the system removes per hour. The heat measurement used for this purpose is British thermal units. One BTU represents the amount of heat required to raise or lower the temperature of 1 pound of water by 1 degree Fahrenheit at a predetermined starting temperature. For each ton in air conditioning, the system removes 12,000 BTUs each hour. That means a 2-ton system would remove 24,000 BTUs each hour, while a 5-ton system would remove 60,000 BTUs per hour. Where does 12,000 come from? It's the amount of heat it would take to melt a 1-ton block of ice.

What's the Difference Between BTUs and Tons?

BTUs and tons are related when it comes to air conditioning. BTU is a measurement of heat. It's the amount of heat needed to raise the temperature of 1 pound of water by 1 degree Fahrenheit. Tons measure the cooling capacity based on how many BTUs it removes per hour. Both measurements can be used to describe the size of an AC system. The manufacturer might call the system a 36,000 BTU air conditioner, which could be the same as a 3-ton system.

Looking to measure the cooling capacity of a window or portable AC unit? You’ll need to measure in BTUs. Try this guide instead.

Why Is AC Tonnage Important?

Air conditioners typically range from 1.5 to 5 tons. Choosing the right size affects how well the system can cool your home, so the tonnage needs to be calculated correctly. If your system is too small, it won't be able to cool your home properly. Your AC will likely run most of the time, which can increase wear on the equipment and cause you to have higher utility bills. Plus, you might never feel completely cool.

You might think going large is the answer, but an oversized system can be just as bad as an undersized system. Your air conditioner will shut off and on frequently, which can increase your power bills and cause more wear on the system. It also won't run long enough to remove humidity from your home like it should, which can potentially leave you feeling uncomfortable. Plus, you'll pay extra for a larger system that you might not need.

Getting just the right amount of tonnage strikes the perfect balance. Your machine will cycle on and off like it should, running long enough to remove humidity but not so long that it hikes up your power bill. Your home will cool off the way you want it to, and your AC won't have extra wear and tear on it.

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Calculating AC Tonnage

Tonnage is something an HVAC pro should calculate when you're getting a new HVAC system. You might be able to estimate the tonnage your home would need based on the square footage, but there are lots of factors about your home that can affect the measure, including:

  • How many windows you have, how large they are and which direction they face
  • Insulation levels
  • Height of your ceilings
  • Number of floors in your home
  • Ventilation
  • Ductwork
  • Landscaping, such as trees that shade your home
  • Number of people in your home
  • Heat-producing appliances

Sizing and installing a new HVAC system is always something you should leave to an experienced HVAC technician. An HVAC technician uses a complex method of calculating the size based on the features of your home. That's why an in-home estimate is important when you're getting quotes for a new HVAC system. A mistake at any stage of the process can make your system less efficient and can cause undue wear and tear on the equipment, which could shorten its life significantly.

Determining the Tonnage of Your Current Air Conditioner

You can often figure out the size of your current system by looking at the model number. You'll usually find the information listed in BTUs. Sometimes, the manufacturer lists the BTUs on the label on the outside AC unit. Other times, it's hidden within the model number. It's often an even, two-digit number ranging from 18 to 60 somewhere within the model number. It might have a 0 in front of it.

If you see 18 or 018, that means it's an 18,000 BTU system. Divide that by 12,000, and you get 1.5, which means you have a 1.5-ton AC. If you see 48 or 048, you have a 48,000 BTU or 4-ton AC. This can give you an idea of what size you need for a replacement, but your new AC doesn't have to be the same as the old one. Your HVAC pro might decide you need a larger or smaller unit.

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Elocal Editorial Content is for educational and entertainment purposes only. Editorial Content should not be used as a substitute for advice from a licensed professional in your state reviewing your issue. The opinions, beliefs and viewpoints expressed by the eLocal Editorial Team and other third-party content providers do not necessarily reflect the opinions, beliefs and viewpoints of eLocal or its affiliate companies. Use of eLocal Editorial Content is subject to the

Website Terms and Conditions.

The eLocal Editorial Team operates independently of eLocal USA's marketing and sales decisions.

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