White paper

Calculating electric drive vehicle GHG emissions

Calculating the greenhouse gas (GHG) emissions attributable to the production of electricity and hydrogen used to power electric drive vehicles is important for understanding the role such vehicles could play in meeting GHG reduction goals, implementing passenger vehicle emissions standards, and providing consumer information about energy efficiency and emissions.

This paper identifies methods to determine e-drive vehicle efficiency, energy supply “well-to-tank” GHG intensity, e-drive vehicle miles traveled, and mode split for plug-in hybrids, which together can provide a basis for calculating edrive upstream emissions. Additionally, it highlights some needs for more and better data—e.g., test cycles used to determine e-drive vehicle efficiency should reflect urbanization trends, aggressive driving, and cabin climate control.

Procedures to account for GHG emissions related to electric vehicles can now be established with reasonable accuracy, based on real-world vehicle efficiency, energy supply carbon intensity, and vehicle usage data. As more experience operating EVs yields more data, the methodology can be updated, but in the meantime it can provide appropriate signals to guide policymakers’s, automakers’, and consumers’ efforts to reduce GHG emissions.