A propane-powered gas burner operates through a process called combustion. The propane that is fed into the burner is combusted using heat, which creates a flame. However, the amount of propane that is being pumped into or consumed by the burner is not equal to the amount of heat that is being put out. You can calculate the propane gas burner consumption using two pieces of information, the efficiency rating of the appliance and the energy output.
Look up the energy efficiency rating for your propane-powered gas burner. This energy efficiency information will be listed on the appliance itself as well as in the appliance's manual. This number is a percentage out of 100.
Look up the total number of British thermal units that your propane gas burner is outputting. This number is also in the appliance's manual.
Multiply the total number of BTUs that your propane gas burner is outputting by 100. If your propane burner is outputting 55,000 BTUs of heat, for example, 55,000 x 100% = 55,000 BTUs of heat.
Divide your number from Step 3 by the energy efficiency rating for your appliance. If your Step 3 number was 55,000 and your energy efficiency rating was 80%, 55,000 divided by 80% = 68,750 BTUs. This means that your propane gas burner is consuming 68,750 BTUs worth of fuel but is only actually producing 55,000 BTUs during operation.