Charging electric cars during the day could help the grid, study finds

To successfully increase Californians’ reliance on electric vehicles over the next decade without overloading the state’s electric grid, more drivers will need to charge their cars during the day, according to a Stanford study.

According to the study published this week in the scientific journal Nature Energy, the state needs to dramatically increase and improve public and workplace charging infrastructure that supports daytime charging, which can make better use of solar power. The increased availability of charging will also make owning electric vehicles more accessible, according to the study.

“If we pay a lot of attention to building a large public charging network wherever people are during the day – at work, in public places… that will be a big win for the network,” said said Siobhan Powell, the lead researcher on the study.

The study, part of Stanford’s Bits & Watts initiative, which pairs researchers with energy industry leaders, used modeling to forecast electric vehicle charging demands in 2035 in 11 Western states, including California. Forecasting that the use of electric vehicles and reliance on renewables will increase over the next 13 years, the team found that improvements to public charging infrastructure – reducing reliance on nightly power-ups – could ensure that plug-in vehicles have the least effect on the power grid.

Electric vehicle owners are likely to be in higher income brackets and charge their batteries at home overnight, often taking advantage of incentives offered by power companies to do so. If these charging habits persist as EV use dramatically increases, peak electricity demand could increase by up to 25%, the researchers say.

While a shift to more daytime charging isn’t expected to stem the rise in demand, it would shift the peak to when California has historically had excess capacity on the grid, thanks to solar power. The change could also help the West prepare for severe strain on its power system during heat waves, which continue to push the grid to its limits.

According to study co-author and associate professor of civil and environmental engineering Ram Rajagopal, by 2035, the year California pledges to end the sale of new fossil-fuel vehicles, the increased capacity will make daytime solar power cheaper. and electrical engineering at Stanford.

“Workplace charging, in particular, aligns very well with solar generation,” Powell added.

Scaling stations that support daytime charging “would improve the impacts of electric vehicle charging, support equitable widespread adoption, reduce emissions, support the integration of renewables, and facilitate the transition to a decarbonized future,” according to the study.

“Building more public daytime charging stations will benefit the network, but can also help provide charging access to more people,” Powell said.

She admits the state needs “millions more” of charging stations to reach its goal of having 5 million zero-emission vehicles on the road by 2030, nearly five times the current amount. But she hopes the research can help shape policy on how and where to implement the stations.

The results don’t mean people should stop charging electric vehicles at home and overnight if it’s best for them, Powell said, because the priority should be to encourage the use of low-emission vehicles or null. But she would like to see the study influence policymakers or companies building charging stations. That way, “it can be the practical choice for people to bill at the time, when it’s best for the network,” Powell said.

Rajagopal, director of Stanford Sustainable Systems Labs, said it could help people get into the habit of daytime charging.

“If we get people used to the right behavior now, when this transition is over, we’ll already be doing the right thing,” he said.