Fuel Economy and Greenhouse Gas Emissions Labeling and Standards for Plug-In Electric Vehicles from a Life Cycle Perspective

Abstract

Reflecting the greenhouse gas (GHG) emissions attributable to plug-in electric vehicles (PEV) on energy and emissions labels, and in vehicle GHG emissions regulations, is complex due to spatial and temporal variation in fueling sources and vehicle use. The relative environmental performance for conventional gasoline vehicles can be reflected by the fuel economy of the vehicle due to the strong correlation between fuel economy and vehicle life cycle emissions. However, this correlation does not hold for PEVs and a more comprehensive emissions accounting methodology needs to be utilized to evaluate their environmental performance. This thesis is organized into two studies. The first evaluates PEV GHG emissions vehicle labeling and the effects of regional grids and regional daily vehicle miles traveled (VMT) on the total vehicle life cycle energy and GHG emissions. The model results indicate that only 25% of the life cycle emissions from a representative plug-in hybrid vehicle are reflected on current U.S. Environmental Protection Agency (EPA) vehicle labeling. Unexpectedly, for two regional grids the life cycle GHG emissions results were higher in electric mode than in gasoline mode. A recommendation is made that labels include stronger language on their deficiencies and provide ranges for GHG emissions from vehicle charging in regional electricity grids to better inform consumers. The second study evaluates U.S. EPA’s GHG emissions accounting methodology and current and future standards for new electrified vehicles. The current approach employed by the EPA is compared with an accounting mechanism where the actual regional sales of PEVs, and the regional electricity emission factor in the year sold, is used to determine the vehicle compliance value. The results showed that in the absence of a major policy shift, the small changes in the emission factors observed suggest that the complexity involved in tracking and accounting for regional PEV sales will not dramatically increase the effectiveness of the regulations to capture PEV electricity related GHG emissions.