A moderate share of V2G outperforms large-scale smart charging of electric vehicles and benefits other consumers

While battery electric vehicles (BEVs) play a key role for decarbonizing the transport sector, their impact on the power sector heavily depends on their charging strategies. Here we systematically analyze various combinations between inflexible, smart and bidirectional (or vehicle-to-grid, V2G) charging of 15 million electric cars in Germany. Using a capacity expansion model, we find that even a moderate share of bidirectional charging below 30% leads to lower system costs than a fully smartly charging BEV fleet. At a V2G share of 50%, costs are even lower than in a system without any BEVs. This means that the flexibility effect of half of the BEV fleet charging bidirectionally outweighs the demand effect of the whole BEV fleet. We show how costs savings are driven by the ability of V2G to serve demand, especially during hours with high residual load. We also explore the distributional effects of respective electricity price changes. While V2G car owners internalize a substantial share of overall cost savings, the benefits increasingly spill over to other electricity consumers as the share of bidirectional charging grows. We conclude that policymakers should focus on enabling a moderate fleet share of V2G rather than on enabling every car to charge smartly.