The rapid rise of electric vehicles (EVs) is a cornerstone of the US strategy to combat climate change.
Yet, a new study reveals a surprising barrier to success: the nation’s outdated transmission grid.
According to research by Northwestern University, electrifying the entire US vehicle fleet won’t significantly cut emissions unless the country also enhances its power grid infrastructure.
Even with ample renewable energy from wind and solar sources, congestion in the transmission grid prevents clean electricity from reaching EV chargers in many parts of the country.
This grid limitation forces reliance on nearby fossil fuel power plants, drastically undermining the emissions-saving potential of EVs.
Grid congestion: A hidden climate obstacle
The US transmission grid operates like a highway for electricity, carrying power over long distances from remote generation sites to urban areas where demand is highest.
But just as traffic jams hinder road travel, congestion on these electrical ‘highways’ can block clean energy from reaching its destination.
Using advanced simulations that modelled electricity demand, vehicle usage, and existing power infrastructure, researchers discovered that in every scenario with high EV adoption, grid congestion became a serious obstacle.
The problem is most acute in urban centres where EV charging demand is high, but the clean energy needed to power those chargers is often generated hundreds of miles away.
Wind farms in the Midwest and solar arrays in the Southwest are producing renewable electricity in abundance, but limited transmission capacity means that this clean energy can’t always reach cities efficiently.
Instead, the grid turns to nearer, and dirtier, fossil-fuel power plants, increasing carbon emissions despite a growing EV presence.
One-third of emissions savings lost without grid fixes
The study’s most comprehensive simulation imagined a future where all gasoline-powered vehicles in the US were replaced with EVs and renewable energy generation equalled that of fossil fuels.
In an ideal world with a fully upgraded transmission grid, this shift would eliminate nearly all transportation-related carbon dioxide emissions.
However, under current grid conditions, about one-third of these potential emissions reductions would be lost.
Even smart charging technologies that align EV charging with periods of peak renewable energy generation can’t overcome the limitations of congested transmission lines.
Strategic transmission grid upgrades are essential
Rather than calling for a complete overhaul of the power grid, the researchers advocate for targeted upgrades.
A modest 3 to 13% increase in transmission capacity could unlock the full climate benefits of EV adoption. These upgrades would involve building new high-voltage lines or reinforcing existing ones, particularly in areas where congestion is most likely to occur.
Crucially, the US grid is divided into three largely independent regions – Eastern, Western, and Texas. Limited ability to transfer power between these regions creates additional inefficiencies.
Strengthening interregional connections and improving coordination would allow clean energy to flow more freely across the country, ensuring that renewable electricity powers EVs regardless of where it is generated.
Clean energy requires clean infrastructure
The findings highlight an often-overlooked truth: decarbonising transportation isn’t just about replacing gas-powered cars with EVs or increasing wind and solar capacity. The transmission grid must be upgraded in tandem to deliver that clean energy where it’s needed.
As the US accelerates its transition to electric mobility, investments in the transmission grid will be essential to maximise environmental benefits.
Without these infrastructure improvements, the nation risks missing a critical opportunity to cut emissions, even in a future filled with electric cars.
