Photos of charging vehicle and solar panel
Key takeaways
Vehicle-to-grid (V2G) chargers enable electric vehicles to behave as a battery network, potentially helping to level out electricity demand throughout the day.
Since this cannot completely offset the increased demands on the grid from EV adoption, the grid should be upgraded first, with V2G charging added later.
The analysis by a team from the National University of Singapore, the Chinese University of Hong Kong, Shenzhen, and University of Michigan Engineering calls for grid upgrades targeting long-term demand expectations to reduce the total costs.
Vehicle-to-grid chargers, which enable grid operators to use plugged-in electric vehicles as a battery network, could help utilities distribute electricity more efficiently. But even with advanced chargers, existing infrastructure cannot supply enough electricity to growing numbers of EVs, computer models from an international team of researchers suggest.
The research team recommends focusing on grid upgrades that plan for anticipated power needs 30 years ahead, while installing cheaper, basic chargers now. Then, when more EVs are on the road, future charger buildouts should prioritize V2G, enabling the upgraded grid to make the most of the expanding fleet of grid-connected batteries.
The study was led by a University of Michigan Engineering researcher, working with colleagues at the National University of Singapore and the Chinese University of Hong Kong, Shenzhen.
Advanced chargers that support vehicle-to-grid (V2G) electricity flow could help smooth out the electricity demand that power plants must meet, as demand rises and falls throughout the day. For example, the vehicles of people who charge at home could discharge after their commutes to help with the evening demand peak and then charge up overnight. Participating drivers could charge their EVs for free or even be compensated for the use of their vehicle battery.
However, this picture is more complicated in urban areas, where home chargers may not be available, and daytime charging adds to the peak. Local solar energy changes the calculation again, with charging vehicles able to store energy when the sun is high and release it at other times of day. The research team wanted to get a handle on what all this means for the grid.
"V2G has been discussed for the past 20 years, and we all know that it is useful in some contexts, but nobody has clearly demonstrated what context that is. Our study lays a foundation to express the context that maximizes V2G capability," said Ziyou Song , U-M assistant professor of electrical and computer engineering and co-corresponding author of the study in Joule.
Case study: EV and solar projections plus census data
The team dug into data from California's Bay Area, which has already seen enthusiastic EV adoption. More than 25% of new cars registered in the area were EVs in 2024. Using census data, the researchers modeled factors such as when households were likely to begin using an EV, where they would likely charge it, potential solar panel installations and the projected rise in baseline energy demand.
They tried different circumstances for the charging build-out, with basic chargers that allow the car to draw energy on demand, those that allow the grid to provide energy anywhere within a set time window, and the V2G chargers that provide power to the vehicle or draw power from it, depending on the needs of the driver and the utility. They also experimented with likely solar panel installations.
With this information in hand, the researchers looked at various approaches to upgrading the grid. In one case, they gamed out installing next-level transformers, transmission lines and other equipment as needed in the near future. In another, they upgraded to match the projected needs of 2050, when nearly all California vehicles are expected to be electric.
"V2G can be a powerful tool for reducing emissions and grid stress, but it isn't a silver bullet. The most cost-effective path forward requires strategically pairing progressive V2G adoption with forward-looking grid investment," said Shunbo Lei , assistant professor of electrical engineering at the Chinese University of Hong Kong, Shenzhen, and co-corresponding author of the study.
The research team had anticipated that upgrading charging infrastructure to V2G might delay the need for grid upgrades, and it can, but they found that the smarter money is on upgrading the grid with 2050 in mind as soon as upgrades are needed. The key reason is that chargers last about a decade, while transformers have expected lifetimes of up to 40 years. Upgrading a transformer in 2030 and again in 2045 represents a significant loss compared to doing a larger upgrade once. In contrast, building out V2G offers a much bigger payoff when more EVs and solar panels are deployed.
"If grid upgrades are inevitable, relying on V2G to delay them is not the most cost-effective approach. In fact, upgrading the grid early turns out to be the more economical strategy in the long run," said Lingcai Xu , first author of the study and a postdoctoral research fellow in the department of built environment at the National University of Singapore.
Beefing up the grid early means that the initial charger build-out can be done with cheaper, basic chargers, and those can be replaced in a decade or so when the advantage V2G capability more than pays for the cost of the charger. V2G will shine particularly when local solar panels can store energy in the local EV network, reducing the load on transmission infrastructure.
Study: Proactive grid investment enables V2G for 100% adoption of electric vehicles in urban areas (DOI: 10.1016/j.joule.2026.102393)
Joule