You may be charging your electric car wrong, new study reveals

Charging your EV in the daytime is good for you and the environment.
Rupendra Brahambhatt
An EV charging at home.
An EV charging at home.


Charging an electric vehicle overnight at home is a common behavior among many EV users, as it seems both practical and convenient to let your vehicle fully charge at night so that you can drive tension-free during the daytime. However, researchers at Stanford University claim that since the number of EV users is increasing, night charging is adversely affecting our electric grids.

The researchers suggest that in order to meet the increased demand at night from residential properties, the existing electrical systems needs to be upgraded. Plus, we would also have to develop an infrastructure powerful enough to support EV charging at homes on a massive scale. This might take a lot of time and cause a spike in home electricity bills as operating costs of power plants would increase.

However, there is a way to limit the cost of generating and storing more electricity for EVs at night and reduce stress on the electric grid. Here is how it can work:

Overnight charging at home vs. daytime charging (at work)

You may be charging your electric car wrong, new study reveals
An EV charging station.

The researchers propose that instead of plugging in their EVs overnight at home if users charge them during the daytime at their workplace or public charging stations. This will prevent our electric grids from overloading at night and would also encourage the rapid development of EV charging infrastructure. Moreover, a major proportion of electricity from non-fossil fuel sources such as solar and wind power is produced and used during the daytime.

On the other side, when electricity demand at homes increases at night, carbon emissions from fossil-fuel-based power grids also increase. Therefore, daytime charging is a more environment-friendly habit as it allows us to use more electricity from renewable sources. The researchers studied the effects of overnight EV charging on the electrical system of the western part of the US, including California, the state with the highest number of EVs on the road.

According to the US Department of Energy, California currently accounts for 39 percent of the total registered EVs in the country. EV sales in the state have already hit the mark of one million in 2022, and recently in August, the authorities signed a rule that bans the sale of gas-powered SUVs, light trucks, and cars from 2035.

While highlighting their findings, the lead author and Ph.D. candidate at Stanford University, Siobhan Powell, told IE, “The scenarios we tested which were dominated by at-home, overnight charging lead to larger increases in peak net demand, larger need for grid storage to shift generation to cover that peak, higher ramping in net demand in the evening, larger amounts of non-fossil fuel generation capacity going unused, and higher operating emissions. The scenarios with more daytime (workplace or public) charging improved on all of these metrics.”

Daytime charging at work should be the new normal

You may be charging your electric car wrong, new study reveals
An EV charger installed inside the parking facility of an office.

Powell and her team found that the western states are required to produce less electricity during the night with daytime charging. It puts less stress on the grid and saves the extra cost associated with storage and generating the extra power for EVs. Moreover, daytime charging allows more and more solar and wind energy, much of which is otherwise wasted.

When asked that charging EVs during the daytime may not sound practical to many users and even policymakers, so how could we convince people and go ahead with this approach," Powell replied, “Charging habits and the availability of different options vary a lot from place to place. In California, workplace and public charging are quite common, and many drivers without access to home charging rely on them completely.”

She further added, “Expanding access to daytime charging options will be an important part of building out the future charging network - both to benefit the grid, as we showed in our study, and to make EVs more accessible to future adopters for whom installing home charging would be too expensive or impossible.”

The researchers also point out that currently, the policymakers are putting in a lot of effort to build the EV infrastructure for the next 10 years, and if a significant amount of that investment and attention gets focused on making daytime charging more accessible and feasible. This could allow the western US states to manage the energy demands of their growing EV ecosystem much better and more efficiently.

The current findings could be an excellent resource for understanding the connection between policy decisions, EV charging infrastructure, and the long-term impact on a region's grid. The researchers hope that policymakers will implement their recommendations in the Western US. They will continue to collect new data to improve their model further.

The study is published in the journal Nature Energy.

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