Electric vehicles can reduce the cost of the power grid by charging during the day rather than at night

The spread of electric vehicles is progressing all over the world, such as the state of California in the United States declaring a ban on the sale of new gasoline vehicles after 2035. When charging an electric vehicle, charging at night when you can get discounts on electricity rates seems like a smart choice, but an analysis by Stanford University shows that in the United States, charging during the day is more costly for the entire electricity grid than at night. It turns out that it can be reduced.

Charging infrastructure access and operation to reduce the grid impacts of deep electric vehicle adoption | Nature Energy
https://doi.org/10.1038/s41560-022-01105-7

Scalable probabilistic estimates of electric vehicle charging given observed driver behavior - ScienceDirect
https://doi.org/10.1016/j.apenergy.2021.118382

Charging cars at home at night is not the way to go | Stanford News
https://news.stanford.edu/2022/09/22/charging-cars-home-night-not-way-go/

As of February 2022, there are 1 million electric vehicles on the road in California, which is expected to grow to 5 million by 2030. A research team at Stanford University analyzed the impact on the power grid as the spread of electric vehicles progressed, and modeled the relationship between electric vehicles and power supply in the western United States until 2035.

The analysis revealed that if 30-40% of the vehicles on the road were to become electric, a major capital investment in the power grid and changes in charging habits would be required. Specifically, if many people continue the charging habit of 'charging at home at night', power demand during peak hours will increase by up to 25%. Since California relies on out-of-state power plants for most of its power supply, the tight supply and demand of power in California also affects surrounding states. Siobhan Powell, a member of the research team, said, ``The impact of the increase in electric vehicles will affect not only California and surrounding states, but also all states in the United States.All states should reconsider the electricity tariff system. We may be forced, ”he argues that capital investment and changes in charging habits are necessary to reduce the risk of tight power supply and demand.

As a change in charging habits, the research team recommends `` charging at work or public charging facilities during the day instead of charging at home at night ''. If 50% of the cars driving in California are electric cars, the amount of power required for charging will reach 5.4 gigawatts, which is equivalent to five large nuclear reactors, if charging is continued at night. On the other hand, when many people start charging during the day, the required amount of power generation will be within 4.2 gigawatts.

Solar power generation is the reason why there is a difference in the amount of power generated at night and during the day. The current electricity rate system follows the days when photovoltaic power generation was not widespread and there was a high risk of tight power supply and demand during the daytime. However, it is said that surplus electricity is now generated during the day due to the spread of solar power generation. For this reason, by charging electric vehicles during the daytime, surplus electricity can be used without surplus.

Ines Azevedo, a member of the research team, said, ``This study shows two important facts. The other is that we need to invest in installing charging infrastructure where people work,” he said, emphasizing the importance of changing charging habits and investing in charging equipment.