Electrification of delivery vehicles will play an important role in decarbonizing the transportation sector. As electricity-generating technologies vary regionally and temporally, where electric vehicles are deployed and when they are charged will determine the greenhouse gas (GHG) emissions and cost consequences of delivery vehicle electrification. We couple a vehicle charging model with a dataset that provides hourly projections of marginal electricity cost and marginal emissions factors across 134 electricity balancing areas in the United States. We calculate the cost and emissions of charging an electric delivery vehicle over a 10-year service life (2021–2030) at different times of day and in different locations. Using a multi-objective optimization framework, we explore two potential goals—minimizing GHG emissions and minimizing cost—and investigate the tradeoffs between those goals. We show emissions ranging from 136 to 485 g CO2/mile, and costs ranging from 0.79 to 3.18 cents/mile depending on location and optimization weighting. We demonstrate the impact of charge time-of-day optimization frequency, showing emissions reductions of 19-62% by choosing the optimal charging time every day, rather than annually. We show that the benefits of electrification are reduced when potential charge times are constrained (e.g., if charging must take place overnight), and we calculate the carbon price needed to align cost-optimized and emissions-optimized charge timing in different regions. Our results highlight the opportunity to reduce cost and emissions by strategically charging at certain times of day and show the importance of accounting for spatial and temporal variability when developing effective carbon-reduction strategies.