Electric car (EV) being charged

Electric car charging (Photo by CHUTTERSNAP on Unsplash)

STANFORD, Calif. — Leaving your luxury electric car charging overnight to have it ready in the morning seems like a good idea in theory. But in reality, research suggests doing so does more harm in the long run. Stanford scientists say that it’s more costly to charge your electric car at night and it could stress out your local electric grid.

Instead, researchers suggest drivers should switch to charging their vehicle at work or in public charging stations. Another added benefit to charging in the daytime at a public station is that it reduces greenhouse gas emissions.

With the effects of climate change more apparent than ever—frequent forest fires, widespread flooding, and stronger hurricanes—car companies are expecting people to start investing in electric-powered cars in the future. For example, California residents are expected to buy more electric cars as the state is planning to ban sales of gasoline-powered cars and light trucks in 2035.

“We encourage policymakers to consider utility rates that encourage day charging and incentivize investment in charging infrastructure to shift drivers from home to work for charging,” says study’s co-senior author, Ram Rajagopal, an associate professor of civil and environmental engineering at Stanford University, in a statement.

So far, electric cars make up one million or 6% of automobile sales in California. The state’s goal is to increase that number to five million electric vehicles by 2030. However, the study authors say that the change from gas to electric will cause a strain in the electric grid when there’s 30% to 40% of cars on the road.

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“We were able to show that with less home charging and more daytime charging, the Western U.S. would need less generating capacity and storage, and it would not waste as much solar and wind power,” explains Siobhan Powell, a doctor of mechanical engineering and lead study author. “And it’s not just California and Western states. All states may need to rethink electricity pricing structures as their EV charging needs increase and their grid changes.”

If half of vehicles in the western United States are electric, the team estimates it would take over 5.4 gigawatts of energy storage—equivalent to five large nuclear power reactors—to charge the cars. However, if people charged their electric cars at work instead of home, the electric demand is expected to go down to 4.2 gigawatts.

California currently uses time-of-use rates to encourage people to use electricity at night such as running the dishwasher and charging cars. However, the authors argue that with growing demand of electric cars, this strategy is outdated and will soon incur high demand with low supply. More specifically, the teams says if a third of homes were to charge their electric cars at 11 PM or whenever electricity rates go down, the local grid would become unstable.

“The findings from this paper have two profound implications: the first is that the price signals are not aligned with what would be best for the grid – and for ratepayers. The second is that it calls for considering investments in a charging infrastructure for where people work,” says Ines Azevedo, associate professor of energy science and engineering and co-senior author.

“We need to move quickly toward decarbonizing the transportation sector, which accounts for the bulk of emissions in California,” Azevedo adds. “This work provides insight on how to get there. Let’s ensure that we pursue policies and investment strategies that allow us to do so in a way that is sustainable.”

The study is published in Nature Energy.

About Jocelyn Solis-Moreira

Jocelyn is a New York-based science journalist whose work has appeared in Discover Magazine, Health, and Live Science, among other publications. She holds a Master's of Science in Psychology with a concentration in behavioral neuroscience and a Bachelor's of Science in integrative neuroscience from Binghamton University. Jocelyn has reported on several medical and science topics ranging from coronavirus news to the latest findings in women's health.

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207 Comments

  1. Eric says:

    Wejo and Palantir have a partnership and have developed a EV Operating System that is designed to be used nationwide to regulate charging station usage to the most optimal times of the day based on power grid demand. Google search “Wejo” and you can read about it. It is very interesting and they have daily data on over 18 million vehicles and are already working with cities on projects such as this.

  2. Farhad says:

    This is the biggest BS I ever heard, charging car during daytime reduces greenhouse gas. How is charging at day any different than charging at night. Its using the same means to produce energy. Especially during night time there is less stress on the grid when most of the industries are shut down at night. Except if you charge during daytime u ll be hiking your bill 3 folds. And office and public places do not have enough port to cover the the charging need for how many cars are out there, also most places its not free. You will be paying a lot more if you are not charging at home. Especially if you have solar, your bills will be significantly less. The only way to reduce this grid stress is make the renewable energy requirement to 70% instead of 30, and place solar on the top of every roof possible where sunlight is available year round, like FL and CA. That is the only solution. Not some stupid theory when and where to charge, focus on not the consumption of energy but the production of energy by increasing twice than it is now, if you want to reduce dependencies on fossil fuel and make most cars EV by 2050.

  3. Scott Fletcher says:

    Everybody, read “One Second After” by Willam Forstchen. Its only fiction for now. Won’t matter EV or ICG, we are all gonna be screwed! LOL

  4. James says:

    Agreed…. that’s exactly what I’m doing. My commute costs free firty free per charge.

  5. Roger says:

    My uncle invited a car to run off of water. The oil companies hired someone to shoot at him. So he didn’t go on and get it going. So now they have electric cars and they still have problems. Mankind will kill mankind lucky for me I’ll be dead soon and I have no children

  6. doug baltzer says:

    stating the results of climate change are more hurricanes, flooding and fires or that they are more extreme is false. Temps have risen about 1 degree in 100 years and deaths from climate or weather related events has dropped by over 90% in that same time. There is no data to show we have more events than we had 100 years ago, so please stop stating incorrect facts.
    The US has reduced its CO@ emissions by over a billion tons since 2005, while China, India, Africa and the Middle East have all increased dramatically over that same time; BUT we are supposed to pay higher utility rates and endure brown outs so we can feel good about our impact on the climate.
    WAKE UP

  7. Dragan says:

    In south Ontario where I live 92% of the electricity comes from hydro and nuclear during night time. I charge my Leaf at night. Intermittent few seconds outages all happen during daytime. (I know that because then I have internet outage.) The problem with mass charging can be easily alleviated by dividing urban areas into zones that have lower price at different times of the day to flatten the demand curve. All EVs can be programmed when to charge, no issue there. Plus Leaf has chargers available to upload electricity back to grid when the demand is high.
    Mining minerals for batteries is polluting, but unlike fossil fuels that once burnt are gone forever, batteries can be recycled. It is surely easier to melt and separate metals than to mine.
    CO2 levels can disrupt life if change too rapidly because the evolution takes time to adapt organisms to new conditions. Nowadays organisms would not thrive in dinosaurs’ times and vice versa. Plants cannot use too much more CO2 as food, because they are adapted to current concentration. If the concertation was higher for long enough then most likely the plants would be able to use it and grow faster. And so our lungs and blood would be different.

  8. geoff says:

    This article is dead wrong if you don’t live in California. California has a surplus of power during the day and imports 35% of its power from neighboring states at night. The author did not state that his comments only pertain to California. The opposite is true in all the other states.

  9. renewableguy says:

    It seems that the match up of production of renewable energy to the charging of electric cars. Different geographic locations of the country will have different power production times. With excess solar, daytime would work very well. If wind production overproduces at night then night time would be a good working time. I don’t see transmission issues at night, it would be time of transmission. Should we still want to charge cars at night, battery storage could be increased to be used for car charging.