UC Davis Institute of Transportation Studies

The charging of plug-in hybrid electric vehicles (PHEVs) will place new loads on the electrical grid. How much and the time of day (TOD) at which users plug in their vehicles will have implications for electricity providers who must meet the additional electrical load required to charge a fleet of PHEVs. PHEV charging could place new burdens on existing electrical infrastructure (substations and transformers) and generating capacity. Information about consumers’ recharging behavior can help utilities and interested parties better plan for PHEVS in the marketplace. PHEVs can run in charge depleting (CD) and charge sustaining (CS) modes and there is uncertainty as to how much travel will be completed in each mode. Accounting for the amount of travel in each mode is crucial in order to accurately assess the fuel economy (FE) benefits, green house gas (GHG) emissions and costs of PHEVs. In 2001, the Society of Automotive Engineers (SAE) promulgated standard J2841 defining the utility factor (UF) as the percentage of travel that can be completed in CD mode for a PHEV fleet with a given CD range. As such, the SAE standard J2841 has a substantial influence on policies regarding PHEVs and their assumed benefits and costs, and has been used by analysts, industry, and policy makers to calculate PHEV corporate average fuel economy (CAFE), GHG emissions, operating costs and Zero Emission Vehicle (ZEV) credits. The analysis described in this report challenges J2841by calculating the observed UF for a fleet of PHEVs driven by 25 Plausible Early Market (PEM) PHEV buyers in a demonstration and market research project. The results suggest that promoting “short range” PHEVs and focusing on popular vehicle-types, rather than upon achieving high CD ranges, could lead to greater total benefits from PHEVs in the early market, through more widespread adoption of PHEVs.