Evaluating California’s Climate Policy Portfolio: Transportation Electrification, Electricity Decarbonization, and Policy Complementarity

Abstract

This capstone evaluates dual-sector climate policy interactions between California’s Transportation and energy sectors. Utilizing a 15-year dataset spanning 64 continuous quarters (2010–2025), this study tests the overarching hypothesis that the effectiveness of transportation environmental policies is endogenous to energy sector decarbonization efforts. Methodologically, EV Adoption rates were modeled via a first-order autoregressive ARIMA (1,0,0) framework, while vehicle and grid emissions intensity were evaluated using multi-interrupted piecewise linear regression. The empirical results reveal a significant cross-sector spillover from the energy sector-focused Senate Bill 100, which accelerated tailpipe emission cuts by -609,981 Metric Tons of CO₂ per quarter. However, SB 100 was also correlated with a reduction in short-term electric vehicle sales by -7,381 vehicles per quarter. Crucially, California’s 2020 EV mandate was not associated with a change in electrical grid emissions intensity (p = .452). This result shows that electrical grid emissions were not significantly influenced by the shift to electric vehicles. These findings offer vital takeaways for states like Washington, as they navigate overlapping regulatory timelines under the Climate Commitment Act. Specifically, any green policies implemented in the energy sector flow downstream to the transportation sector, amplifying outcomes relating to green transportation policies. Therefore, the state’s legislature should consider implementing tandem or bundled policies that utilize this downstream effect to maximize their desired environmental outcomes