Parked EVs save money, reduce emissions, provide energy to homes

By relying on their vehicle's batteries for more than just transportation, EV drivers could save thousands on their energy bills and cut carbon emissions

Peer-Reviewed Publication

University of Michigan

News Release 16-Dec-2025

Electric vehicles batteries to power households could save their owners thousands of dollars in bills while cutting emissions from the power grid, according to new research from the University of Michigan and Ford Motor Company.

Published in the journal Nature Energy, the team investigated scenarios related to vehicle-to-home charging, or V2H. This emerging technology lets EV drivers tap into energy from their vehicles' batteries to help manage power to their homes. It's almost like using EVs that are parked in garages as generators, but instead of burning gasoline, they provide electricity from their batteries that have been charged by the grid.

"Putting vehicle batteries between the electricity grid and homes makes it possible for homes to buy electricity for all household uses when it is cheap and clean—for example, in the afternoon, when there is a lot of solar power—and to store it in the car’s battery for later use," said Parth Vaishnav, an assistant professor in the University of Michigan's School for Environment and Sustainability, or SEAS.

"If you're buying an EV because you want to cut greenhouse gas emissions—or if you're making an EV because you want to cut greenhouse gas emissions—this tells you that, in addition to reducing greenhouse gas emissions from transport, the EV could also help cut building sector greenhouse gas emissions." 

According to the study, supported by the Ford-University of Michigan Alliance Program, V2H could save EV owners 40 to 90% of their charging costs over the lifetime of the vehicle. That translates to between $2,400 to $5,600 in vehicle lifetime savings.

Furthermore, V2H could reduce lifecycle greenhouse gas emissions from a household’s electricity use by 70 to 250%, which would amount to cutting between 24 and 57 tons of lifetime carbon dioxide emissions. That'd be equivalent to driving a small gas-powered SUV for 80,000 to 190,000 miles, or 80 to 190 one-way flights between New York and Los Angeles. The reduction can surpass 100% when it more than makes up for emissions from the extra electricity needed to drive the car, Vaishnav said.

V2H in the U.S.A.

Vaishnav stressed that this idea is not new, but the discussion around V2H has been largely about its possibility and benefits in principle. What he and his colleagues have done is provided a more thorough and comprehensive outlook for the benefits of V2H in practice across the country.

The team evaluated the impact of V2H using a representative mid-sized SUV considering a variety of factors that vary by location. That included grid energy cost and emissions, housing stock and even the temperature outside, which affects energy efficiency. The team broke the contiguous U.S. into 432 regions defined by shared climates and grid conditions to map out the different impacts.

"We have a lot of geography-based insight," said Jiahui Chen, lead author of the study and a doctoral student in SEAS. For instance, not all regions saw the same benefit. 

But the research showed that V2H enabled greenhouse gas reductions that more than fully offset emissions from charging in regions that account for 60% of the U.S. population. In parts of Texas and California, the cost savings of V2H compared to conventional charging can be so great that it more than pays for the electricity needed for driving.

"When people think of EV charging, it's usually thought of as a burden, a cost that is added to your electric bill," Chen said. "But, with this kind of technology integration, we can make charging an asset." 

A work in progress

While the study's take-home message is that V2H has serious economic and environmental upside, the team also stressed that there are important caveats to consider. One way of looking at the study is that it provides decision-makers with an estimate of whether equipping homes for V2H is worth it, Vaishnav said.

“Another important factor is that the technology to control charging and maximize V2H isn't fully plug-and-play in the U.S. yet, but it is actively being demonstrated with local utilities in various U.S. markets” said Hyung Chul Kim, a research scientist at Ford and a coauthor of the new study.

"This capability is promising but still in its early stages. We're working with utilities to identify the best use cases for them, and we’re also determining ways to optimize overall battery lifetime."

Solutions have been developed and are being tested to deliver on that optimization with utilities and customers. 

"Ultimately, the goal is that drivers won’t have to change anything—they would park and plug in their EVs as normal, then technology running in the background automatically finds the best charging and discharging times,” Kim said.

While that infrastructure begins to scale, the team hopes its collaboration can also lead to a more immediate shift in the way people think about energy and their vehicles.

"We know that vehicles are parked the vast majority of the time and, so as this infrastructure develops, there's a great opportunity here," said Robb De Kleine, a life cycle research analyst with Ford and a coauthor of the new study. 

"As we try to decarbonize the grid, we need energy storage to be able to do that. A lot of the time, the first instinct is to build stationary storage. But EVs could serve as electricity storage devices," De Kleine said. "They just happen to have wheels on them."

The research team also included James Anderson, a technical leader of sustainability and environmental science at Ford, and Greg Keoleian, a professor with SEAS. The team also published a corresponding policy brief about the work.