Electric Vehicle Miles Traveled (eVMT) from PHEVs Used in Fleet Applications: Results from a Demonstration Project

Plug-in Hybrid Electric Vehicles (PHEV) allow users to reap the benefits of an electric drivetrain while retaining the option to use gasoline when necessary. This flexibility can be valuable, however, it raises the question of how to measure the performance of PHEVs? The environmental and economic benefits of PHEVs increase in proportion to electric miles driven. This is a function of the battery size, drivetrain characteristics and efficiencies and operator driving and charging behaviors. Common practice surrounding environmental and economic assessments of PHEVs has been to assume that vehicles will be charged once per driving day. In reality, other factors may influence the driving and charging behavior of fleet operators using PHEVs, especially, since fleet operators do not pay for fuel or purchase the vehicles themselves and, as such, have little direct financial incentive to plug-in. A 2-year demonstration project involving prototype PHEVs provided the opportunity to collect real world data on fleet operator driving and charging patterns which is supplemented with in-person interviews and a web based survey. Overall some users drove more electric miles than expected (up to 1.3 times more) while 75% of users drove less electric miles than was predicted. Based on results from interviews and a web survey the authors identify practices among organizations such as user training and motivation, vehicle assignment, and charging infrastructure as the potential source of this variation in user performance. The results emphasize the potential for driver behavior and organizational decisions to affect the electric driving of PHEVs.