During the recent September heat wave in California there was a lot of press and misinformation about the impact of charging EVs on an already taxed California grid. But while EVs can pull a significant amount of power from the grid, as the recent threat of power outages in California proved, most EV drivers can and do charge during non-peak hours of the day.

According to estimates from the California Energy Commission (CEC), electric vehicles in California only consume 0.4% of grid demand during the peak hours of 4-9 pm. While the actual draw of EVs over a 24-hour period is much higher of course, except for commercial vehicles, driving on road trips, and those consumer vehicles that are used for work, most EVs will sit parked 22-23 hours per day. This means that when these vehicles are charged, they can be managed and optimized around the cost of electricity, the source of electricity, and the time of day to lessen the impact on the grid.

Historically, when EV drivers charged at home, a large percentage would do so overnight when electricity rates (and grid demand) were lower, often through utility EV time-of-use rates. But while rates are lower in the middle of the night and there is very little demand on the grid, in most regions a large percentage of grid power will be from non-renewable sources such as natural gas or coal. (This can vary widely as California uses almost no coal and states in the northwest often generate most of their electricity 24 hours a day from large hydro.)

But especially in states like California where solar is a large and growing source of power, and more solar power is often generated during the day than is used, we will start to see a shift of when some EV drivers charge, to during the day when solar power is dominant from the current middle of the night practice.