Efficiency and Emissions of Electric and Hydrogen Light- and Heavy-Duty Vehicles

Abstract

<div>Life cycle analyses suggest that electric vehicles are more efficient than gasoline internal combustion engine vehicles (ICEVs). Although the latest available data reveal that electric vehicle (EV) life cycle operational efficiency is only 17% (3 percentage points) higher than a gasoline ICEV, overall life cycle efficiencies including manufacturing for EVs are 2 percentage points lower than for ICEVs. Greenhouse gas (GHG) emissions of EVs are only 4% lower than ICEVs, but <i>criteria</i> emissions of NOx and PM are approaching or exceeding two times those of gasoline ICEVs. Significant reductions in electric grid emissions are required to realize EV’s anticipated emission benefits. In contrast, hybrid electric vehicles (HEVs) have over 70% higher efficiency and 28% lower GHG emissions than today’s EVs. For heavy-duty trucks using today’s <i>gray</i> hydrogen, produced by steam–methane reforming, overall life cycle efficiencies of ICEs and fuel cells are 63% higher than electric powertrains using today’s electric grid, but 25% lower than diesel-fueled ICEs. GHG emissions of ICEs and fuel cells using <i>gray</i> hydrogen are 34% lower than electric powertrains using today’s grid, but are over 50% higher than diesel-fueled ICEs. Only 1% of today’s hydrogen is <i>green</i>, derived by electrolysis using renewable energy. Using <i>green</i> hydrogen, life cycle efficiencies of ICEs or fuel cells are 36% lower than with <i>gray</i> hydrogen. GHG emissions of <i>green</i> hydrogen-fueled ICE or fuel cell powertrains, although reduced by 69% relative to <i>gray</i> hydrogen, are nearly twice those of an electric powertrain using renewable electricity.</div>