Assessing the potential of combined vehicle-to-grid and rooftop photovoltaics strategies for reshaping city-level power load profiles

The rapid growth of electric vehicles (EVs) and rooftop photovoltaics (RPVs) is transforming urban energy systems, their combined impacts on city-level power load demand remain underexplored. This study develops a scenario-based framework to evaluate combined impact of vehicle-to-grid (V2G) discharging strategies and RPV deployment on representative weekday hourly net load, peak and valley loads, and load fluctuation intensity across 41 cities in the Yangtze River Delta (YRD). Results indicate that the combined strategies integrating orderly EV charging and discharging with RPV generation in scenario S9 can reduce the peak load by approximately 21.9 GW, lower the peak–valley difference to around 51.6 GW, and reduce the load fluctuation intensity by approximately 50 % compared with the baseline scenario in 2030 in YRD region. Lower electricity demand cities, such as Lianyungang, exhibit up to 70 % reductions in midday load, whereas high-load metropolitan areas, such Shanghai, show relatively limited improvements. However, when an excessive number of EVs participate in V2G or the RPV penetration becomes too high, load may experience stronger fluctuations. Policy recommendations include promoting coordinated EV charging and discharging, and the integrated deployment of RPV and energy storage systems to enhance energy system resilience.