UC Davis Institute of Transportation Studies

To explore the potential energy impacts of widespread PHEV use, an innovative, three-part survey instrument collected data from 877 new vehicle buyers in California. This analysis combines all the available information from each respondent—driving, recharge potential, and PHEV design priorities—to estimate the energy impacts of the respondents’ existing travel and understandings of PHEVs under a variety of recharging scenarios. Results suggest that the use of PHEV vehicles could halve gasoline use relative to conventional vehicles—the majority of this reduction being due to increases in charge sustaining (CS) fuel economy. Using three scenarios to represent potential boundary conditions on PHEV driver recharge patterns (unconstrained, universal workplace recharging, and off-peak only charging), we estimate tradeoffs between the magnitude and timing of PHEV electricity use. In the unconstrained “Plug and Play” recharge scenario, recharging peaks at 6:15 p.m., following a far more dispersed pattern throughout the earlier part of the day than anticipated by previous research. PHEV electricity use could be increased through policies increasing non-home recharge opportunities (e.g., the “Enhanced Workplace Access” scenario), but most of this increase occurs during daytime hours and could contribute to peak electricity demand (depending on a given region’s definition of “peak”). We also demonstrate how deferring all recharging to off-peak hours (8:00 p.m. to 6:00 a.m.) could eliminate all additions to daytime electricity demand from PHEVs. However, in such a scenario less electricity is used due to the elimination of daytime recharge opportunities and less gasoline is displaced. Overall, policy, technology, and energy providers may use this information to understand whether their plans, designs, and goals align with these present empirically informed understandings.