Why Virtual Mileage Can Threaten Vehicle-to-Grid

Vehicle-to-grid (V2G) technology is gaining interest, particularly for electricity trading using electric vehicle (EV) batteries. This study focuses on the economic impact of V2Ginduced vehicle degradation. Unlike traditional approaches that estimate costs based on battery capacity loss, upcoming "virtual mileage" regulations aim to provide a more tangible metric. Virtual mileage, deduced from the energy reinjected onto the grid by the vehicle, is meant to represent a similar wear as real mileage. However, it should be noted that this metric is flawed as it tends to overestimate vehicle degradation since it tacitly includes wear on components that are not used during V2G (for instance: tires, brakes), and overlooks other factors like battery calendar ageing: for example, an EV with high virtual mileage could retain better battery health than one stored at full charge. Virtual mileage could hence significantly affect EV residual value, around ~1 c€ per virtual kilometre in order of magnitude, translating to ~0.05 € per discharged kWh. This depreciation would pose a substantial barrier to V2G profitability. Using simulations of EVs in the French day-ahead electricity market for 2019, the study finds that accounting for devaluation reduces average annual V2G benefits to just 6.96 €/EV, compared to 29.2 €/EV without it. The paper highlights the aforementioned limitations to virtual mileage and advocates alternative metrics such as the state-of-health to assess vehicle degradation, aiming to enhance the feasibility of V2G.