Electric vehicles (EVs) are often seen as a key solution in the fight against climate change.
But a new study from Northwestern University warns that simply switching from gas-powered cars to EVs isn’t enough—at least not without a major update to the U.S. electricity grid.
The research, published in Nature Communications, shows that even if the U.S. had enough renewable energy to power every EV, the current power grid wouldn’t be able to deliver that clean energy where it’s needed.
This bottleneck, called grid congestion, means that many EVs would end up charging with electricity from nearby fossil fuel power plants, undercutting the environmental benefits of going electric.
Professor Adilson Motter, who led the study, explains that the biggest problem isn’t the availability of renewable power—it’s the outdated infrastructure that moves electricity across the country.
Just like traffic jams on a highway, congestion on the power grid prevents clean energy from reaching EV charging stations. This forces the system to fall back on more polluting sources.
To better understand the problem, Motter’s team used real-world data on driving habits and the layout of the U.S. electric grid.
They ran computer simulations showing what would happen if every vehicle in the country became electric and clean energy became the main power source. The result? Without upgrades, one-third of the possible reduction in carbon emissions would be lost because of the grid’s inability to deliver clean power efficiently.
The issue is especially noticeable in cities, where EV charging demand is highest. Renewable energy is often generated far from these areas—like solar power from deserts or wind from rural plains. But the long-distance transmission lines needed to carry that power into cities are often too limited or congested.
The good news is that the researchers also found a solution. They discovered that upgrading just 3 to 13% of the grid’s transmission capacity could dramatically ease congestion and allow more clean energy to flow. This doesn’t mean rebuilding the entire grid. Instead, they suggest targeted upgrades in the areas with the worst congestion.
The U.S. power grid is divided into three main regions—Eastern, Western, and Texas—that don’t share electricity efficiently. Improving the links between these regions would help renewable energy reach the areas where it’s needed most, especially for EV charging.
Motter says the grid was never designed to move energy on such a large scale. “It grew bit by bit,” he explains. “Now, with EVs and renewable energy becoming more common, it’s time for smarter, more strategic improvements that fit today’s energy demands.”
Without these changes, clean energy will remain stuck on the grid—unable to reach the vehicles that need it most.
