Abstract:

Vehicle electrification is a promising pathway of de-carbonizing on-road transportation. Plug-in electric vehicles pose great potentials to de-carbonize the transportation sector. To jump-start their market deployment, regulations in China, the U.S., and the European Union provide preferential treatments, including counting a single plug-in electric vehicle with multipliers (super-credits) in calculating sales-averaged emissions (regulation dilution effect) and considering zero emissions for the electric mileage by omitting electricity generation emissions (regulation leakage effect). This study quantifies greenhouse gas emission increases due to these two effects in the three markets. The authors show that plug-in electric vehicles sold in 2012–2025 in the three markets will result in greenhouse gas emission increases of more than 1 billion tonnes of CO₂ equivalent through 2050 relative to the case without the two effects. The increase is 671, 280, and 143 million tonnes in China, the U.S., and the EU, respectively. The dilution effect causes an increase of 615 million tonnes, and the leakage effect 479 million tonnes. As the plug-in electric vehicle market grows, their super-credits should be gradually withdrawn, and well-to-wheels emissions need to be considered to achieve holistic greenhouse gas emission reductions. Future regulations should be carefully designed to incentivize new technologies while mitigating the risk of increasing emissions elsewhere so that the intent of environmental regulations is not compromised. The modeling in this study has shown that internal combustion engine vehicles (ICEVs) will continue to dominate on-road vehicle stocks for a long time. Limiting and eventually eliminating the PEV dilution and leakage effects can directly and indirectly promote advancement in ICEV technologies and low-emission fuels for a low carbon transportation future.