How to Compute the Size of a Furnace

Locate the BTU Capacity of the Furnace

• 1

  Open the service panel on the furnace. The panel is usually located at the top side of the unit.

• 2

  Turn the thumb screws with your fingers or a flat-head screwdriver to remove the service panel.

• 3

  Locate the small metal plate or paper sticker inside the service panel housing. Read the Btu capacity on the label.

Size a Furnace for Your Home

• 4

  Measure the length and width of your home in feet. Measure the ceiling height of your home.

• 5

  Go to the Btu Heat Requirement Calculator website in the Resources section. Other, similar calculators can be found online by performing a simple search.

• 6

  Enter your target temperature in the Btu Heat Requirement Calculator form. The target temperature is the approximate temperature you expect to maintain in your home. The U.S. Department of Energy recommends that insulated homes maintain a target temperature of 68 degrees Fahrenheit to provide sufficient indoor climate comfort at minimum energy costs.

• 7

  Enter your lowest outside temperature in the Btu Heat Requirement Calculator form. This number should reflect the general lowest temperatures your region experiences. For example, if you live in the Northeast and regularly experience temperatures of -10 degrees Fahrenheit during the winter, enter in "-10." Do not enter irregular temperatures.

• 8

  Enter the dimensions of your home in the Btu Heat Requirement Calculator form.

• 9

  Click "Calculate" to receive the general furnace size requirement for your home in your climate