Code of Federal Regulations Title 10. Energy 10 CFR Pt. 474, App. Appendix to Part 474—Sample Petroleum–Equivalent Fuel Economy Calculations

Example 1:  An electric vehicle is tested in accordance with Environmental Protection Agency procedures and is found to have an Urban Dynamometer Driving Schedule energy consumption value of 265 Watt–hours per mile and a Highway Fuel Economy Driving Schedule energy consumption value of 220 Watt–hours per mile. The vehicle is not equipped with any petroleum-powered accessories. The combined electrical energy consumption value is determined by averaging the Urban Dynamometer Driving Schedule energy consumption value and the Highway Fuel Economy Driving Schedule energy consumption value using weighting factors of 55 percent urban, and 45 percent highway:

combined electrical energy consumption value = (0.55 * urban) + (0.45 * highway) = (0.55 * 265) + (0.45 * 220) = 244.75 Wh/mile

Since the vehicle does not have any petroleum-powered accessories installed, the value of the petroleum equivalency factor is 82,049 Watt–hours per gallon, and the petroleum-equivalent fuel economy is:

(82,049 Wh/gal) (244.75 Wh/mile) = 335.24 mpg

Example 2:  The vehicle from Example 1 is equipped with an optional diesel-fired cabin heater/defroster. For the purposes of this example, it is assumed that the electrical efficiency of the vehicle is unaffected.

Since the vehicle has a petroleum-powered accessory installed, the value of the petroleum equivalency factor is 73,844 Watt–hours per gallon, and the petroleum-equivalent fuel economy is:

(73,844 Wh/gal) (244.75 Wh/mile) = 301.71 mpg