Parasitic loads are generated by accessories that run the engine or provide power to vehicle systems like cooling fans, alternator, actuators, power steering, air brake compressors, and liquid pumps. Furthermore, fuel consumption from conventional diesel driven vapor compression refrigeration systems can be as high as 40% of the fuel consumed from the truck’s engine. Serving these loads more efficiently can reduce heavy trucks’ total fuel use by 3–7% at minimal cost, with payback periods under 2 years.
Bockholt, Wendy, and Matthew Kromer. 2009. Assessment of Fuel Economy Technologies for Medium- and Heavy-Duty Vehicles. TIAX LLC.