Transportation electrification is expected to be a key factor in climate change mitigation, with global electric vehicle (EV) adoption accelerating due to technological advancements and supportive policies. The growing integration of EVs into the power grid presents significant challenges and opportunities, requiring a deep understanding of both the power and transportation sectors. This dissertation investigates the impacts of transportation electrification on greenhouse gas emissions, electric distribution system stress, and energy equity within the context of California's ambitious climate policies. The research encompasses personal vehicles, medium- and heavy-duty trucks, shared mobility services, and implications for disadvantaged communities.The power system operates across three levels: generation, where electricity is produced; transmission, which transfers it over long distances; and distribution, where it is delivered to end-users. This dissertation investigates various issues at both the bulk power system (generation and transmission) and distribution levels. At bulk level, the impact of vehicle electrification is examined alongside two other emerging trends in the transportation sector – shared mobility and autonomous vehicle, by evaluating the environmental benefits of shared autonomous electric vehicles (SAEVs). Current studies simplify SAEV travel demand projections with private vehicle travel data and lack investigation coupling SAEV charging load with grid operation, especially with respect to an evolving power system. Unlike privately owned EVs, SAEVs are expected to exhibit usage patterns more similar to ride-hailing services. Using real-world Uber and Lyft trip data, I simulate SAEV demand and evaluate emissions by integrating their charging load into a grid dispatch model that optimizes renewable capacity expansion. Results show that SAEVs can be more than five times less carbon-intensive than private internal combustion vehicles (ICVs) on a per-mile basis under the Californian power grid. Aligning SAEV charging schedules with renewable energy generation maximizes the emission benefits, and the addition of a carbon tax can further amplify the advantage of smart charging in the cost-effectiveness of emission mitigation by approximately 1.5 times. At distribution level, the network characteristics and electricity usage patterns are highly diverse. This study conducts a novel quantification of EVs’ impact on distribution grids at unprecedented scale and resolution, and tackles the challenge of capturing the spatial and temporal diversity in EV charging demand. The study estimates that 67% of distribution feeders will require upgrades by 2045, with the projected need for infrastructure upgrades totaling 25 GW, at a cost of $6 to $20 billion. Despite the additional infrastructure costs, increased electricity consumption could reduce overall electricity rates by $0.01-$0.06/kWh by 2045. Residential feeders will face higher stress than commercial ones, and shifting home charging demand can potentially reduce upgrade costs. The research also addresses equity concerns, incorporating medium- and heavy-duty EV charging load into the distribution-level analysis. An evaluation of spatial disparities in grid resource access shows that disadvantaged communities, identified by higher CalEnviroScreen scores, are expected to have a higher share of feeders needing upgrades but with a lower average upgrade size per feeder. Despite varying capacity upgrade requirements, the distribution of costs and benefits from the upgraded grid infrastructure is expected to be relatively proportional across communities.