Estimation of Energy Use by Plug-In Hybrid Electric Vehicles Validating Gamma Distribution for Representing Random Daily Driving Distance

The fuel and electricity consumptions of plug-in hybrid electric vehicles (PHEVs) are sensitive to the variation of daily vehicle miles traveled (DVMT). Although some researchers have assumed that DVMT follows a gamma distribution, such an assumption has yet to be validated. On the basis of continuous travel data from the Global Positioning System for 382 vehicles, each tracked for at least 183 days, the authors of this study validated the gamma assumption in the context of PHEV energy analysis. Small prediction errors caused by the gamma assumption were found in PHEV fuel use, electricity use, and energy cost. Validating the reliability of the gamma distribution paves the way for its application in energy use analysis of PHEVs in the real world. The gamma distribution can be easily specified with few pieces of driver information and is relatively easy for mathematical manipulation. Validation with real world travel data enables confident use of the gamma distribution in a variety of applications, such as the development of vehicle consumer choice models, the quantification of range anxiety for battery electric vehicles, the investigation of the role of charging infrastructure, and the construction of online calculators that provide personal estimates of PHEV energy use.