Developing a Utility Factor for Battery Electric Vehicles

As new advanced-technology vehicles are becoming more mainstream, analysts are studying their potential impact on petroleum use, carbon emissions, and smog emissions. Determining the potential impacts of widespread adoption requires testing and careful analysis. PHEVs possess unique operational characteristics that require evaluation in terms of actual in-use driving habits. SAE J2841, "Utility Factor Definitions for Plug-In Hybrid Electric Vehicles Using 2001 U.S. DOT National Household Travel Survey Data," published by SAE in 2009 with a revision in 2010, is a guide to using DOT's National Household Travel Survey (NHTS) data to estimate the relative split between driving in charge-depleting (CD) mode and charge-sustaining (CS) mode for a particular PHEV with a given CD range. Without this method, direct comparisons of the merits of various vehicle designs (e.g., efficiency and battery size) cannot be made among PHEVs, or between PHEVs and other technologies. The dedicated battery electric vehicle (BEV) is now becoming a viable alternative to conventional vehicles and other advanced vehicles (like HEVs and PHEVs). However, a shortcoming persists in current comparisons between BEVs and other vehicles. The BEV cannot satisfy all individual driving needs and most likely will be used alongside other household vehicles (which use petroleum fuel). To properly assess impacts of widespread BEV adoption, a " BEV Utility Factor" will be necessary. Using the most current NHTS data with individual trip data, several charging and vehicle-use scenarios are presented to bookend the expected utility of electric drive capability at any given BEV range. This analysis reveals that a real-world 75-mile-range BEV with a safety reserve of 10 miles has virtually the same electric drive utility as a PHEV with a 38-mile electric-only (CD) range.