How to Calculate Direct Efficiency for a Gas Fired Boiler

The efficiency of our heating systems has become more important as the cost of energy has increased. Since the 1970s oil crisis, our boilers have risen from 70 percent efficient up to 96 percent efficient in modern condensing units. These gains have been made by extracting most of the heat from the exhaust products, closing off the exhaust vents when not in use and shutting down the pilot light. Calculating the efficiency of your unit is done with a little information from its data plate.

Things You'll Need

• Calculator

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Instructions

1. • 1

     Look for the boiler's data plate. This is usually inside the front cover on the unit or on the outside of the boiler's case.

   • 2

     Record the "Input BTU" number from the data plate.

   • 3

     Record the "Output BTU" number from the data plate.

   • 4

     Divide the "Output BTU" by the "Input BTU" using a calculator. Multiply the result by 100. The result is the percentage efficiency of the unit or the amount of energy transferred to the building from the energy consumed.