Electric Vehicles Tested for Grid Energy Storage in Delaware Pilot

A pilot project in the U.S. state of Delaware has shown that electric vehicles (EVs) can store renewable energy during periods of excess supply and return it to the grid during high demand. The project involved four Ford EVs owned by energy company Delmarva Power, which were retrofitted for vehicle-to-grid (V2G) charging.

Researchers monitored the vehicles throughout 2025 and calculated that each could earn up to $3359 annually if the supplied energy was sold at market prices. At least 90 percent of new electricity generation is renewable, but sources like solar and wind produce power intermittently.

EVs, which are driven only about 5 percent of the time and often parked and plugged in, could serve as distributed storage to balance the grid. This approach might cost about one-tenth as much as building dedicated battery farms, according to Willett Kempton at the University of Delaware, who led the project.

technology requires converting direct current (DC) from EV batteries back to alternating current (AC) for the grid, which involves safety standards to prevent hazards. Some companies, including Volkswagen and Nissan, offer wall chargers that handle this conversion, similar to those used for solar panels.

However, these chargers can cost thousands of dollars. Other manufacturers, such as Tesla, BYD, and Renault, are developing EVs that perform the DC-to-AC conversion internally. This could add only a few hundred dollars to the vehicle's cost. A rivalry exists between DC-based and AC-based V2G systems, with AC potentially being cheaper and more scalable, according to Alex Schoch at UK electricity retailer Octopus Energy.

For widespread adoption, buyback tariffs are needed to allow EV owners to profit from supplying energy. In 2024, Octopus Energy launched the UK's first V2G tariff and partnered with BYD to lease compatible vehicles and chargers. Many upcoming EVs will be V2G-capable, potentially providing gigawatts of distributed capacity.

V2G could help balance grid supply and demand in real time but may strain existing infrastructure. A study from the National University of Singapore recommends early grid upgrades to handle increased charging demands cost-effectively. Lead author Liangcai Xu and co-author Ziyou Song noted that significant upgrades are necessary to support large-scale V2G.

The concept of V2G dates back to 1997, when Willett Kempton began investigating it, but it remains mostly in test programs in the US, Europe, Japan, and China. Coordination among vehicle makers, utilities, and governments is required for broader implementation.

As renewable energy grows, V2G could enhance grid reliability and support more renewables.