Do electric vehicle purchase incentives drive equity? The relationship between incentive policies and vehicle registration rates across California

Transportation electrification needs to occur quickly to combat climate change. To that end, clean vehicle and charging incentive policies have increasingly been implemented at the state and federal level. However, previous research has not evaluated the distributive equity of the full suite of electric vehicle (EV) purchase incentive programs at a spatially-resolved scale, or characterized the quantitative relationship between these programs and EV registration levels. We fill these gaps by focusing on California given its unique incentive program history, with nearly a million clean vehicle incentives distributed since 2010 – totaling approximately $1.9 billion – through six purchase incentive programs. We compile data from each of these vehicle purchase incentive programs, as well as on residential fleet type registration, population and neighborhood characteristics, and measures of socioeconomic and environmental burden in each of the more than 8000 census tracts across the state. We find that the number of registered clean vehicles has sizably increased over time throughout most regions — yet adoption rates remain persistently low in lower-income and state-identified disadvantaged communities. Only 16 % of clean vehicle purchase incentive funds have been delivered to households in disadvantaged communities, falling short of Justice40-aligned aims, with more equitable outcomes coming from regionally-administered as compared to statewide programs. To assess the effect of vehicle purchase incentives on clean vehicle adoption rates, we employ negative binomial multivariate regression models using census tract-level panel data from 2015 to 2022. Our primary model results show that, controlling for other factors also influencing registration rates, the level of incentives affects clean vehicle registration, but also attenuates over time. We also find that the effect of incentives is larger in state-identified disadvantaged communities than for the rest of the population. We conclude by outlining implications for future and more equitable EV incentive policy design and implementation. • $1.9 billion in clean vehicle incentives distributed across California since 2010. • Only 16 % of incentive funds have reached disadvantaged communities. • Negative binomial regression was used to assess incentives' impact on EV adoption. • Incentives positively impact EV adoption rates, but the effect weakens over time. • Incentives have a stronger effect in state-identified disadvantaged communities.