By Anne Fonda

HVAC capacity is the production capability of a heating or cooling unit. Air conditioning capacity and heating capacity are measured in tons or BTUs.

When it comes to your air conditioner, tons refers to cooling capacity rather than the actual weight of the AC unit. Tons are also known as tonnage. Determining the capacity in tons that you need to cool your home involves precise AC sizing. 

Correct sizing involves taking numerous factors into account and entering them in to perform a Manual J load calculation. Factors HVAC professionals consider include:

• Your climate region
• Your annual cooling needs
• The size of your home in square feet
• The layout of your home and the number of stories
• Ceiling height
• Number and size of windows
• Skylights
• Patio doors
• Sun exposure
• Existing ductwork
• Current insulation and ventilation
• Current energy efficiency of the home
• Other heat-generating appliances

You can also estimate AC sizing using the square footage of your home, as indicated by the AC sizing chart below. But remember, this is only an estimate. Work with an HVAC company to get a system with the right capacity to cool and heat your home.

Notice that one ton = 12,000 BTUs. More on that below.

BTU stands for British Thermal Units. One BTU refers to the amount of heat that’s needed to raise or lower one pound of water by one degree Fahrenheit. The heating capacity of a furnace or heat pump is measured in BTUH or BTUs per hour. But BTUs can also be used to measure the capacity of central air conditioners and ductless HVAC systems. 

To get a furnace or heat pump (or dual-fuel system) that can comfortably heat your home no matter the weather, work with an HVAC professional. Know that the colder your climate zone, the more BTUs, or heating capacity, you will need.

Wondering what size HVAC unit you need or how many BTUs your furnace should have? Contact your local Trane dealer for precise system sizing.

Anne Fonda, Content Writer

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A Content Writer with Trane Technologies, Anne Fonda researches topics and writes for Trane® and associated residential HVAC brands. She works in collaboration with Trane Technologies subject matter experts, offering easy-to-understand, informative content on complex topics. Her goal is to help consumers make informed decisions on the products and services they need.

She has written for HVAC and other service provider websites for over 16 years. Before transitioning to web content writing, Anne had a 14-year stint as an award-winning journalist. She graduated cum laude from the University of Missouri-Columbia School of Journalism.

When she’s not working, Anne enjoys playing word games, reading, gardening, spending time with family, and visiting gardens and museums.

Expert review by Kimberly Sexton, Senior Systems Engineer