In 2008, University of Michigan researchers won a $2 million grant to make parked EVs feed power back to the grid. 18 years later, some firms have reached commercial offerings, turning some parked cars into grid-connected batteries

An electric car parked overnight may look completely inactive. Its battery, though, could become a useful piece of America's electricity system. That is the central idea behind vehicle-to-grid technology, which allows compatible electric vehicles to send electricity back toward the grid. Instead of treating every parked EV as a finished charging load, utilities could eventually treat groups of them as flexible energy storage.

The concept is not new, but the technology around it is changing. Researchers at the University of Michigan received a $2 million National Science Foundation grant in 2008 to study vehicle-to-grid integration. Their work examined how plug-in hybrid vehicles could connect transportation and electricity systems more closely.

What makes the idea compelling is the mismatch between how often people drive and how often their vehicles sit still. A car may spend most of a day parked at home, work or elsewhere. During those hours, a compatible battery could potentially help manage electricity demand without taking the vehicle away from its owner.

Parked EVs Are Quietly Turning Into Local Grid Batteries

Vehicle-to-grid technology is sometimes described as turning electric cars into mobile power plants. That description sounds dramatic, but it misses the more practical opportunity. The batteries are better suited to providing quick bursts of flexibility than replacing large power stations.

Electricity demand constantly moves up and down throughout the day. Grid operators must respond when supply and demand briefly fall out of balance. Frequency regulation helps make those corrections, and batteries can respond quickly because they do not need time to start burning fuel.

That is where a connected fleet becomes interesting. Hundreds or thousands of vehicles can be coordinated as one larger resource. Each individual battery contributes a small amount, while software manages the combined response for the grid.

A single electric car has already demonstrated the idea

The concept has been tested in the real world for years. On October 18, 2007, researchers at the University of Delaware connected an AC Propulsion electric car directly to the PJM grid. The vehicle responded to real-time control signals and provided frequency regulation.

PJM has continued exploring the technology since that early demonstration. Its current work describes electric vehicles as potential mobile storage devices that can charge and discharge according to grid needs. In one earlier demonstration, electric BMW Minis earned roughly $100 per month per car for providing regulation services.

More recent demonstrations have moved toward production vehicles and modern charging standards. PJM and Delmarva Power have worked with Ford vehicles to demonstrate bidirectional charging, showing how the concept could move beyond specialized research cars.

How does electricity move from a car back to the grid?

The basic idea is surprisingly straightforward. A normal charger mainly moves electricity in one direction, from the grid into the vehicle. A V2G system needs equipment that can safely reverse that flow when the grid needs support.

The car must be capable of bidirectional charging, and the charging equipment must support it as well. Software then becomes the traffic controller, deciding when the battery should charge, hold energy or discharge. The system also has to protect the driver's expected range before the vehicle is needed.

The U.S. Department of Energy describes these batteries as mobile storage resources. They can support buildings, provide backup electricity and, with the right arrangements, participate in grid programs.

Could drivers actually make money from their parked cars?

That possibility is real, but it needs some qualification. Vehicle owners generally would not receive a simple payment every time their car sends electricity into the grid. Instead, revenue could come through utility programs, aggregators or wholesale electricity markets.

PJM's earlier demonstrations showed that electric vehicles could earn payments for grid services. The DOE also says bidirectional vehicles can generate revenue through demand management and other grid-related services.

Still, American drivers should not assume V2G will immediately pay hundreds of dollars each month. The DOE says programs that compensate vehicles for grid services are not yet widely available. Equipment costs, utility rules, market structures and vehicle compatibility remain important barriers.

The battery question could decide whether V2G succeeds

There is another concern that matters to anyone who owns an EV. Batteries do not last forever, and repeated charging and discharging can affect their condition. That means a V2G program must create enough value to justify whatever additional battery use occurs.

Researchers are still working through that trade-off. The DOE's 2025 Vehicle Grid Integration Assessment identified vehicle impacts, grid services, standards, cybersecurity and business models as major areas requiring further development.

Drivers also need control over their vehicles. Someone leaving for work at 7 a.m. cannot discover that their car was used heavily overnight and lacks enough charge. A practical V2G system must therefore work around human schedules rather than treating every battery as permanently available.

Why could this matter as America's EV fleet grows?

America is confronting an unprecedented surge in electricity demand. Technology companies are building data centers at a record pace, adding tens of gigawatts to regional power grids as artificial intelligence workloads run continuously. At the same time, the national electric vehicle fleet is expanding rapidly. While millions of plugged-in cars initially look like an added strain on local utilities, their collective storage capacity tells a very different story.

The average passenger EV holds roughly 65 kilowatt-hours of battery capacity, meaning a million parked cars contain enough stored energy to supply hundreds of thousands of homes during peak hours.

When linked together through bidirectional chargers, these parked vehicles form dynamic storage networks capable of smoothing out heavy industrial loads. Instead of firing up expensive fossil-fuel peaker plants during late-afternoon power spikes, utilities can tap into the excess energy sitting in driveways and office parking lots.

This approach softens the strain caused by round-the-clock data center operation while compensating drivers for sharing their vehicle power. As energy grid operators race to support expanding digital infrastructure, leveraging electric cars as flexible grid assets offers a pragmatic way to keep the lights on without expanding carbon emissions.

Fleets may get there before ordinary drivers

The first large-scale winners may not be individual homeowners. Electric school buses, delivery vehicles and commercial fleets have predictable routes and long periods when they are parked. That makes them easier for utilities and aggregators to coordinate.

A school bus, for example, may return to its depot each afternoon and remain there overnight. Its battery can potentially provide grid support during those hours while still retaining enough energy for the next school day.

That predictability is valuable because V2G depends on coordination. The DOE's current strategy focuses on larger demonstrations, technical standards, cybersecurity and workable business models before widespread deployment can happen.

The original appeal of vehicle-to-grid technology was simple: a parked car does not have to remain an idle battery. Nearly two decades after early U.S. demonstrations, that idea is still being tested rather than fully commercialized. The question now is less about whether an EV can share electricity, because demonstrations have shown that it can. The harder question is whether automakers, utilities and drivers can build a system that makes sharing that energy worthwhile for everyone.