UC Davis Institute of Transportation Studies

Estimating greenhouse gas (GHG) emissions of plug-in hybrid vehicles (PHEVs) is challenging because PHEVs are powered by gasoline and grid electricity—in a variety of proportions across individual consumers. Previous GHG estimates emissions postulate consumer behavior and simplify interactions with the electricity grid. We construct PHEV emissions scenarios to address inherent relationships between vehicle design, driving and recharging behaviors, seasonal and time-of-day variation in GHG-intensity of electricity, and total GHG emissions. From a survey of 877 California new vehicle buyers we elicit driving patterns, time of day recharge access, and PHEV design interests. The elicited data differ substantially from those used in previous analyses—including substantial interest in PHEVs with no true all-electric driving. We construct electricity demand profiles scaled to one million PHEVs and input them into an hourly California electricity supply model to simulate GHG emissions scenarios. Compared to conventional vehicles, consumerdesigned PHEVs cut marginal (incremental) GHG emissions by more than one third in current California energy scenarios and by a quarter in future energy scenarios— -2- reductions similar to those simulated for all-electric PHEV designs. Across the emissions scenarios realization of long-term GHG reductions depends on reducing the carbon intensity of the grid.