Quantifying V2G system value under carbon abatement pathways

Amid the deep integration of global energy transition and transportation electrification, vehicle-to-grid (V2G) technology has shown significant potential in mitigating renewable-energy fluctuations, enhancing grid stability, and reducing carbon emissions. However, existing studies lack a quantitative analysis of V2G system value composition and do not clearly reveal the substitution–complementation mechanisms between V2G and other energy sources. This study develops a region-specific capacity expansion model incorporating V2G technical features, source-grid-load synergy, and regional cost differences. K-means clustering is first used to identify representative regions based on power generation and consumption structures and electric vehicle stocks. An analytical framework is then constructed to decompose V2G system value into substitution value (SV), representing cost savings from displacing traditional generation, and scarcity value, representing additional value when V2G supplies electricity during periods of supply-demand tightness or low-carbon flexibility shortage. In addition, substitution-complementation indicators are proposed to quantify V2G interactions with other energy sources across multiple scenarios. Chinese case studies show that the V2G SV decays rapidly with increasing participation rate and exhibits strong regional heterogeneity. System value is mainly driven by variable renewable energy (VRE) and hydropower penetration: it rises in VRE-dependent regions under carbon constraints, but follows a U-shaped trend in hydropower-rich regions. The 100% participation case is used only as a boundary scenario, whereas the practically relevant range is 20%–50%. Hydropower partly crowds out V2G flexibility value in hydropower-rich regions during the early-to-mid stages of decarbonization. Sensitivity analysis further shows that battery degradation costs reduce, but do not eliminate, V2G system value.