ARB Research Seminar

This page updated September 10, 2019

Advanced Plug-in Electric Vehicle Travel and Charging Behavior

Photo of Gil Tal, Ph.D.

Gil Tal, Ph.D, University of California, Davis

September 24, 2019
Cal EPA Headquarters, 1001 "I" Street, Sacramento, CA



Zero-emission vehicles are key to California's strategy to meet air quality and climate goals by reducing transportation-related emissions. This research project examined the driving and charging behaviors of drivers of plug-in hybrid electric vehicles (PHEVs) and battery electric vehicles (BEVs), in order to improve projections of GHG and criteria air pollutant emissions, and to inform refueling infrastructure planning efforts. This study collected information from PHEV and BEV households between 2015 and 2018 by: 1) surveying over 11,000 California PHEV and BEV buyers, 2) logging approximately one year of data for all vehicles in more than 200 PHEV and BEV households, and 3) conducting structured interviews of a subset of the logged households

Results reveal that vehicles with longer electric ranges (both PHEVs and BEVs) result in lower emissions compared to vehicles with shorter electric ranges. The percent of zero-emission miles (i.e., electric vehicle miles traveled, or eVMT) driven by PHEVs increases with the vehicle's electric range, from an average of 15% for the Prius Plug-in to 68% for the longer-range Chevrolet Volt. However, considering the overall total miles traveled by all household vehicles, PHEV households in the study only achieved an average of 9 to 45% eVMT depending on the PHEV model and the total number of household vehicles. In contrast, BEV households drove an average of 34% to 73%, with longer-range BEVs driven more than shorter-range BEVs (both overall and as a percent of total household vehicle miles traveled).

Vehicle charging behavior is primarily determined by the availability of workplace charging and access to free charging. PHEV drivers tend to charge more often than BEV drivers. Over half of all PHEV and BEV drivers (53%) charge only at home, about a third (33%) combine home with other locations, and the 14% who do not charge at home mostly use work charging and, in some cases, fast charging opportunities. BEV drivers are more likely than PHEV drivers to use level 2 charging.

The interviews show that early PHEV and BEV drivers may still be learning about their vehicle's performance and capabilities, even months or years after they acquired one, but they may continue to use the car based on old information. Carpool lane access incentives, when cited as a primary purchase incentive for PHEV buyers, correlate with reduced charging frequency and higher annual mileage, leading to a decrease of eVMT overall and as a fraction of total miles traveled.

The results of this study, which will be used to inform CARB's Advanced Clean Cars program, point to factors that affect the environmental impact of PHEVs and BEVs including charging behavior, cost and access to charging, household fleet composition, and vehicle usage.

Speaker Biography

Gil Tal, Ph.D., is the Director for the Plug-in Hybrid & Electric Vehicle Research Center at the University of California, Davis (UCD). He is also affiliated with The China Center for Energy and Transportation and the Graduate Groups in Transportation Technology, and Policy at UCD. Dr. Tal is a leading expert on electric vehicle travel behavior, as well as understanding the role that incentives and infrastructure play in the electric vehicle market worldwide. He also researches the electrification of new mobility services and their impact on the electric grid. Dr. Tal holds a Ph.D. in Transportation Technology and Policy from UCD and a M.A. in geography and environmental policy and planning from the Hebrew University in Jerusalem.

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