EP 1110-1-8
(Vol. 9)
31 July 03
SECTION VIII. OPERATING COST
2.22
Operating Cost Elements
The total operating cost is the sum of the following five elements: fuel, FOG,
repairs, tire wear, and tire repair.
2.23
Fuel Cost
Fuel costs are computed for each gas, diesel, or electric engine. If the unit of
equipment has two engines, as in the case of a truck crane, this methodology treats
each engine separately for fuel costs. The hourly fuel cost for each unit of equipment is
shown under the column heading FUEL in table 2-1 and table 2-2. If the unit of
equipment has no engine, no fuel cost will be shown. Hourly fuel costs are calculated
for each engine, as expressed in the following formula:
Fuel Cost/hr = Horsepower (hp) x Fuel Cost/Gallon (gal) x Fuel Factor (gal/bhp-hr)
a. Horsepower is the engines rated horsepower. All horsepower ratings for
engine-driven equipment are listed with the equipment description in table 2-1.
b. Fuel Cost/Gallon is based on values shown in appendix B. See chapter 3
for fuel cost adjustments.
c. Fuel Factor - Gas or Diesel Fuel. The fuel factor in gallons per brake
horsepower-hour (bhp-hr) is listed in appendix D for both average and severe
conditions. Fuel factors are also listed for both the engine powering the main
equipment (prime engine) and the engine providing power to the carrier vehicle. For
severe conditions, the fuel consumption rate is 30 percent greater than the average
condition rate. Gas or diesel fuel factors are computed by using the following formula:
Horsepower Factor (HPF) x lbs Fuel per bhp - hr
Fuel Factor (Gal/bhp - hr) =
lbs of Fuel per Gal
Where:
(1) HPF is the horsepower factor used in the fuel and electricity
consumption formulas and represents an average percent of full-rated horsepower
being used by the engine. The fuel consumption factors, which are shown in
appendix D under column headings Fuel Factor-Equipment and Fuel Factor-Carrier, are
computed based on the HPF shown under these column headings. This HPF is an
estimate of the engine load under average working conditions. It is necessary to modify
the rated horsepower as engines and motors in actual production do not work at their
full-rated horsepower at all times. Periods spent at idle, travel in reverse, traveling
empty, close maneuvering at part throttle, and operating downhill are examples of
conditions that reduce the HPF. Professional judgment regarding cycle time and
equipment loading is applied to determine this average HPF. Normal field application
2-7
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