Does BEV always help to reduce CO2 emission? impact of charging strategy

The environmental impact of battery electric vehicles (BEVs), which are an integral part of climate change mitigation measures, depends on charging strategies, such as uncontrolled charging, controlled charging (V1G), and discharging (V2G). However, the impact is unclear because power system operation involves the cost of carbon dioxide (CO2) emissions and flexibility requirements for imbalances caused by renewable energies. To clarify the robustness of the environmental impact of BEVs, we assessed the interactions between CO2 prices and flexibility requirements in Japan in 2030 using a production cost model. The results showed that uncontrolled charging increases CO2 emissions, whereas V1G or V2G reduces them. Further, the impact of BEVs was non-monotonic with respect to CO2 prices, implying that policymakers should carefully evaluate CO2 prices to achieve decarbonization as BEVs do not always reduce CO2 emissions. This study provides useful insights for policymakers in countries with low-cost, inflexible, and high-emission power plants.