California’s Electric Vehicle Demand Peak is 2 percent of the Grid’s Peak Demand

California needs to charge electric vehicles during day, not night, to save grid, study says

California should phase in charging stations at night to reduce the strain on its grid during peak hours, a new study finds.

After analyzing data from across the state, the report from the Department of Water Resources finds California’s energy use and demand during nighttime hours was higher than during the day, and is the main factor driving the use of electricity by plug-in electric vehicles.

The study, in the latest version of California’s electric vehicle plan, also found that the most efficient charging stations were located on the state’s freeways — in the worst and least environmentally sound cities in the state.

“You want that charging station to be in the middle of the freeway and on the shoulder, not in the middle of an urban area,” said Ben Kieschnick, an energy specialist at UC Berkeley, who led the study.

The report finds that the peak demand by electric vehicles during the day is 2 percent of what is required for grid stability. After setting the peak demand during the day at 2 percent of the peak demand, the peak demand during the night climbs to 8 percent. Peak demand during the day is primarily met by “standby” generation, in the form of electricity from other utility-owned plants. This means that the most energy is “deregulated” or used by utilities that are subject to greater price competition.

The study finds that the electric vehicle demand peak occurs when the amount of grid-supplied electricity used to charge a battery decreases to 0.8 percent of maximum demand. This happens in California at 3:01 p.m. in the afternoon.

During this time of day, during peak hours, the electric vehicle demand can easily be met with energy generated by other utilities (the “snow” generation). In other words, the peak demand during the day is covered by the “snow” generation. During the night, the electric vehicle demand

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