How is Capacity Measured in Heating and Cooling Equipment?

Have you wondered how to determine the right size for your heating or cooling system? Unlike clothes or other items that you buy, you certainly can’t bring it home, try it out, and then return it if it doesn’t fit just right.

Air Conditioning Replacement

You will be happy to know that it’s a much more precise process. But one thing that can get confusing for homeowners is what measurement system to use and what the commonly used abbreviations mean. In this article, we’ll address both those issues.


Both heat pumps and furnaces us British Thermal Units (BTU, for short). This measures the amount of energy used to raise the temperature of one pound of water a single degree (Fahrenheit). In general, the higher the BTU number, the more powerful the system is – and more indoor space it can service.

However, bigger isn’t always better. Calculating the right BTU load for your home depends on a handful of factors, including:

  • Square footage of home
  • Height of ceilings
  • Location and climate
  • Type, size, and number of windows
  • How much insulation is in your walls and ceiling

You may also see BTU associated with air conditioning, but this is a slightly different measurement. In this case, the BTU rating is how much energy is required to remove heat from the indoor air. When comparing AC systems, there’s another important number you need to know.


Air conditioning (as well as some heat pumps) also use the Seasonal Energy Efficiency Ratio (SEER) that measures how efficient the unit is at cooling air. The higher the SEER number, the more energy-efficient the unit is, which is better for the environment and saves you money on monthly energy bills. 

The minimum SEER rating for ACs produced today is 13, while some high-end systems have SEER ratings between 22-26. To put things into perspective, older ACs can have SEER numbers around 8 or 9. 

Even if your air conditioning has a high SEER rating, it’s still important to take other steps toward making your home energy-efficient such as using a programmable thermostat, using a fan to circulate air, closing the blinds to block heat from sun rays, and sealing gaps in your windows and doors.

Air conditioning installation

Now that you know two of the most important terms for heating and cooling power, you should have a better idea of what to look for in a new system for your home. If you have any questions or are ready for an estimate from a trusted company in the Evansville, IN area, call Baylor Heating & Air Conditioning, Inc. at (812) 425-8435.

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