Letting EVs take a load off the grid could result in 'negative emissions' while saving drivers money
University of Michigan
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New research from the University of Michigan and Carnegie Mellon University shows how emerging electric vehicle charging approaches could spur the growth of renewable energy and reduce emissions from power generation.
view moreCredit: J. Chen et al. Environ. Sci. Technol. 2025 (DOI: 10.1021/acs.est.5c06944) Image used under a CC BY license.
Letting electric vehicles strategically charge from and discharge to the grid could spark environmental and public health benefits for Americans, according to a new study from the University of Michigan and Carnegie Mellon University.
For one, it could reduce greenhouse gas and other air emissions in a way that would more than offset what's produced when charging EVs. In addition to mitigating climate change, this reduction in emissions would help alleviate some of the damaging health impacts and costs.
Furthermore, it could also help drivers sell stored energy to the grid and recoup some of their charging costs while incentivizing the construction of more renewable energy generators.
"These new installations would decarbonize not only EVs, but other parts of the whole power system," said Jiahui Chen, a lead author of the new study and U-M doctoral student in environment and sustainability. "By adding EV flexible loads, you actually reduce emissions from the entire grid."
The project was funded by U-M's School for Environment and Sustainability, as well as Carnegie Mellon's Department of Engineering and Public Policy and Department of Mechanical Engineering.
After solar panels and wind turbines are built, they provide nearly free energy without any greenhouse gas emissions. Unfortunately, nature doesn't work on our schedules. Without robust storage solutions, the clean energy that's made when the sun's shining and the wind is blowing is wasted when its supply exceeds the demand.
Companies are starting to roll out new large-scale storage technologies to try and change that. But researchers have also realized a growing number of Americans could have another established solution sitting in their garages: electric vehicles. By strategically charging EVs and enabling them to send their stored energy at appropriate times to the grid, Americans could access more affordable energy with less emissions.
"You'd think if you're buying more electricity, you'd be creating more emissions, but it turns out you can actually reverse it, if you charge your vehicle at the right time. We call it 'negative vehicle emissions,'" said study senior co-author Jeremy Michalek, professor of mechanical engineering and of engineering and public policy at Carnegie Mellon.
Central to these gains are two intertwined ideas that aren't brand new, but also aren't yet widely implemented in the U.S. The first is this idea of charging at the right time, or smart charging, when the grid is flush with energy from renewable sources.
The second key component is what's referred to as vehicle-to-grid, or V2G. With V2G, EV drivers could sell their stored clean energy to the grid when demand is high, instead of power plants needing to burn more fossil fuels to meet energy needs.
"There are times when wind and solar are generating so much power that it cannot be consumed and, sadly, we have to waste that," Chen said. "We can use EVs to absorb that otherwise wasted very cheap, very clean energy. We can then use that energy at a later time, when it would cost more, and avoid burning fossil fuels to make it."
The combination of smart charging and V2G would support a system that incentivizes the building of more renewable energy plants. Once they are built, these resources can inject clean energy into the grid whenever they produce it, because wind and sunshine are free while oil and gas are not.
"Once you have that wind and solar in place, it generates first. It displaces coal and natural gas even when EVs aren't charging. It's like the EVs trigger the building of these plants that then can run and displace fossil fuels all the time," Michalek said. "This low carbon infrastructure can supply everybody else who uses electricity as well."
The team is not the first to consider the ramifications of V2G and smart charging. But it is the first to model their impacts in a more comprehensive manner that accounts for their influence on the evolution of renewable energy in the country.
"We tend to think of these things as separate and static. For example, there's a bunch of studies—including ones that I've done and Jeremy has done—that try to figure out whether electric vehicles cut emissions or not with a static grid," said Parth Vaishnav, senior co-author of the study and U-M professor of environment and sustainability.
"But as things start electrifying and start interacting, it's incomplete to answer questions about one system without accounting for how it might change how another system is built and operated."
This modeling also used a fairly conservative outlook, Chen said. For example, it did not assume federal incentives, like the recently expired tax credits in the Inflation Reduction Act for renewable energy. The researchers also considered scenarios that allowed for the deployment of large, stationary battery banks to store energy from the grid. While the details varied in those scenarios, the take-home messages remained the same, the authors said.
"EVs could still produce a lot of substantial benefits," Chen said. "You could say there is an additive relationship."
Michael Craig, U-M associate professor of environment and sustainability and of industrial and operations engineering, also contributed to the study, as did Matthew Bruchon, who worked on the project as a doctoral student at Carnegie Mellon.
Journal
Environmental Science & Technology
Article Title
Negative Electric Vehicle Emissions: Vehicle-to-Grid Can Incentivize Enough Wind and Solar Investment to Reverse EV Charging Emissions
