To use the formula below, remember to use a decimal for the appliance heating efficiency you are assuming (see Table 2). You must first convert the Btu content of the fuel per unit to millions of Btu by dividing the fuel's Btu content per unit by 1,000,000. For example: 3,413 Btu/kWh (electricity) divided by 1,000,000 = 0.003413.