It’s been almost 30 years since Willett Kempton came up with the startling claim that stationary electric vehicles could feed unused power back into the electric grid. In 1997, the University of Delaware professor argued that the then-emerging cars represented a significant source of unused power for the grid, since they were typically parked nearly all the time.
By plugging into the grid when they didn’t need the power themselves, EVs could become effectively a major source of storage, and even a source of income for their owners, he said.
It was a compelling claim but in order to be widely adopted, the principles of “Vehicle to Grid”, or V2G, would need to be supported by new industry standards, regulation, technology, and policies by state and federal governments – and it quickly became apparent none of those would change as fast as Kempton and his colleagues wanted.
Now, conditions are changing, thanks to a convergence of new government policy, increased demand for power storage, cash that’s potentially available to EV owners for feeding their power back to the grid, and the expectation that EV prices will fall soon. That combination could draw more drivers into a market that already represents around 10 percent of annual U.S. sales of new cars.
Coupled with rising utility demand for electric reliability, and urgent efforts by the regional grid operator, PJM, to make sure demand doesn’t soon exceed supply – as experts predict -- it could be that V2G’s time has come.
“Whether it could scale cost-effectively was an open question, and we’ve proven that it can – with the right combination of policies, standards and technology,” Kempton said in a mid-April statement asserting that V2G is how to unlock the earning potential of EVs.
This time around, V2G has attracted the interest of Delaware’s main electricity distributor, Delmarva Power, which supports the idea that fitting EVs with V2G equipment can support grid reliability, add customer value, and improve system flexibility as electrification grows.
Delmarva participated in a four-year pilot program whose results showed that V2G is indeed scalable, in part because it can pay drivers for installing technology that can feed power back to the grid, as well as taking power from it when required.
The pilot found that a V2G-enabled passenger EV could earn its owner as much as $3,359 a year, based on 2021-25 power prices, for storing and supplying power to the grid during the average 96 percent of the time that the vehicles are parked. Heavier EVs such as fleet vehicles, delivery trucks or school buses could earn some $9,000 a year each, the UD-Delmarva team concluded.
The pilot, which also included Ford Motor Co., tested the V2G concept on a small fleet of Delmarva Power EVs retrofitted with “biodirectional” charging technology that can both store extra energy from the grid when there’s a surplus, and discharge that energy when needed.
“V2G-enabled EVs can help the grid stay balanced, strengthening grid resilience and reliability, especially during peak demand and extreme weather events,” the team said in a joint statement.
The conclusion that V2G is scalable depends not on any individual retrofit of EVs with V2G technology but on the manufacture of new EVs that are already V2G-compatible.
At least one such car maker has already stated its interest in doing so, Kempton said, while refusing to identify the manufacturer because of his non-disclosure agreement with the company. “We expect to see at least one EV model in 2027 that will have this as a built-in capability,” he said in an interview.
The outlook for V2G is also brightened by a change in federal rules that requires regional transmission organizations like PJM to allow coordination by makers of EVs and charging systems. At the state level, Delaware lawmakers are considering proposed changes to a law that would aid the advance of V2G technology.
Kempton and other advocates want lawmakers to amend Title 26 of the Delaware Code on electric utility restructuring to facilitate V2G, according to a bill by Sen. Stephanie Hansen (D-Middletown), who chairs an Energy Stakeholders Group that includes energy-company executives, environmentalists and Delaware’s Public Advocate.
“The legislation has not been introduced as of now, but conversations amongst Senator Hansen and stakeholders are active regarding a path forward on this effort,” Joe Edelen, a spokesman for Senate Democrats, said this week.
After growing rapidly for several years before the second Trump administration, the rate of EV sales has flattened in the last year, probably because of the end in September 2025 of both a $7,500-per-vehicle federal tax subsidy for new EVs, and $4,000 for used EVs, Kempton said.
The previous federal support reduced a premium of around $10,000 on the purchase price of a new EV compared with an equivalent internal-combustion model, Kempton said. But the prospect of an EV owner making $3,000 or more a year for selling his or her power back to the grid may persuade potential EV owners to take another look at the vehicles. The addition of V2G technology by manufacturers would increase the retail cost of a new EV by only about $200, Kempton said.
For Delmarva Power, the pilot program showed that V2G is indeed scalable because it used real-world conditions to test the idea’s viability, said Matthew Ford, a spokesman for Delmarva’s parent, Exelon. By using commercially available EVs, alternate-current charging equipment, and emerging standards designed for broad deployment, “the project successfully combined utility interconnection, communications standards, and market participation rules in a way that can be replicated across large fleets,” he said.
The pilot showed that V2G-enabled vehicles can provide grid services during periods of high demand, Exelon found.
“While not a replacement for generation or infrastructure, V2G has the potential to help reduce peak demand and improve system flexibility by leveraging assets that already exist, and particularly as EV adoption increases,” Ford said.
PJM, which operates the grid in Delaware plus 12 other northeastern and midwestern states and the District of Columbia, said V2G has yet to be used at scale but already represents a large storage resource that could help consumers by cost-savings or providing direct payments. The nation’s largest grid operator, serving some 67 million people, has been under pressure from state and federal governments to ensure that electric supply rises to meet sharply higher expected demand in the next few years. PJM has been supporting emerging technologies like V2G for more than a decade, said spokesman Jeff Shields.
The availability of V2G means that utilities and grid operators can use EVs to store energy at a fraction of the cost of batteries, Kempton said.
“If you had big batteries or trailers it would cost thousands of dollars so this is very low-cost storage. For a utility like Delmarva Power, they have to balance supply and demand, and having storage makes it easy to do that,” he said. “Your customers can even get paid to provide a really valuable service. It makes it much easier to make the grid reliable at a much lower cost.”
