Clean Energy Available, But Not for Electric Vehicles

The Critical Role of the Power Grid in Climate Change Mitigation

Even with an abundance of renewable energy, merely transitioning from gas-powered vehicles to electric vehicles (EVs) won't be sufficient to combat climate change—unless the U.S. modernizes its transmission grid, according to a new study by Northwestern University.

The research highlights that if all gas-powered vehicles in the country were replaced with EVs, the existing power grid would not be able to deliver the cleanest electricity to charging stations. This "grid congestion" would result in increased reliance on nearby fossil fuel plants, which undermines the environmental benefits of electrification.

Understanding the Problem

The study identifies the primary issue: while renewable energy sources are available, the current grid infrastructure is unable to efficiently transport this energy to where it is needed. This bottleneck limits the effectiveness of EV adoption in reducing carbon emissions.

Adilson Motter, a professor at Northwestern University and lead researcher of the study, explains that the main challenge lies not in the availability of renewable energy but in the ability to transmit it. He states, “The power lines are congested, and that leads to congestion-induced CO2 emissions.”

Motter, who is also the director of the Center for Network Dynamics, conducted the research alongside Chao Duan, a former Research Assistant Professor at Northwestern. Their findings were published in the journal Nature Communications.

How the Grid Works

The power grid functions similarly to a highway system, transmitting electricity across the United States. After being generated at power plants, electricity travels long distances through high-voltage transmission lines before reaching substations. From there, it is distributed to homes, businesses, and EV charging stations.

To understand how electricity moves through the grid, the researchers combined data on vehicle usage and power grid infrastructure. They used advanced computer models to simulate the flow of electricity under different scenarios of vehicle electrification and renewable energy generation.

In every scenario with high EV adoption, grid congestion was identified as a critical obstacle. As more people switch to EVs, the demand for electricity increases, particularly in urban areas. However, renewable energy sources like wind and solar are often located far from cities, such as on rural wind farms or in desert regions.

Despite the availability of clean energy, the current grid capacity is often insufficient to deliver it to where it's needed, including EV charging stations. As a result, the grid has to rely on closer, more polluting power plants that burn coal, oil, and gas.

The Impact of Grid Congestion

In one of the study’s most ambitious simulations, researchers converted the entire U.S. vehicle fleet to electric. If the grid had adequate transmission capacity, this shift could eliminate nearly all vehicle-related CO2 emissions once renewable energy matches nonrenewable energy generation. However, with current grid constraints, one-third of those potential emissions savings would be lost.

Motter notes that while EV charging schedules can be optimized to align with renewable energy generation, efficient use of clean energy still depends on having enough transmission capacity to deliver it where it's needed.

Smart, Targeted Upgrades

To address this issue, the researchers calculated the additional transmission capacity required. They found that increasing the existing grid’s transmission capacity by as little as 3 to 13% would significantly reduce congestion. This could involve building new high-voltage lines or expanding existing ones, allowing more clean power from remote wind and solar farms to reach cities and suburbs where EV charging demand is highest.

Motter emphasizes that the entire grid does not need to be rebuilt. Instead, he suggests targeted upgrades in areas where congestion is most likely to occur. The U.S. grid is divided into three largely independent regions—Eastern, Western, and Texas—with limited ability to transfer power between them. Improved connections and coordination among these regions would help clean energy reach the areas that need it most.

The Future of the Grid

Motter explains that power grids began as local networks, where consumption was close to generation. Over time, they evolved into nationwide systems. While no one wants to redesign the grid from scratch, he argues that targeted upgrades are necessary to reflect the large-scale reach of today’s grid.

The study provides valuable insights into the importance of modernizing the power grid to support the transition to electric vehicles and renewable energy. By addressing grid congestion, the U.S. can unlock the full potential of EV adoption in reducing carbon emissions and combating climate change.