Renewable energy sources now account for at least 90 percent of new electricity generation capacity being installed. However, the intermittent nature of solar and wind power means electricity supply will inevitably fluctuate, dependent on sunshine and wind conditions. A pilot project conducted in Delaware, United States, has demonstrated a novel approach: electric vehicle (EV) owners could potentially generate thousands of dollars annually by allowing their parked vehicles to function as a distributed battery system. This system would store surplus electricity during periods of high supply and discharge it when demand peaks.
Data suggests that the average electric vehicle is operational for as little as 5 percent of the time, often remaining parked and connected to the power grid. Willett Kempton of the University of Delaware, who led the project, posits that rather than investing in large-scale battery farms, power companies could achieve grid stability by drawing electricity from these readily available vehicles. Specifically, energy could be extracted during peak demand in the mornings and evenings, and the vehicles then recharged during off-peak hours. This arrangement would allow EV owners to sell electricity at a premium while simultaneously reducing costs for the grid.
Kempton estimates that an electric vehicle plugged in for 95 percent of its non-driving time can provide grid storage at approximately one-tenth the cost of conventional battery installations. This capability, he explains, could significantly enhance the reliability of any electrical system and bolster the capacity to integrate increasing amounts of renewable energy.
The Delaware project involved four Ford EVs, owned by the energy company Delmarva Power. These vehicles were modified to facilitate vehicle-to-grid (V2G) charging, enabling them to supply electricity back to the power network. Kempton and his team meticulously monitored the V2G charging performance throughout 2025. Based on the quantity of electricity these cars delivered to the grid, it was calculated that each EV could have accrued as much as $3,359 annually if the energy was sold at prevailing market rates.
The Long Road to V2G Commercialization
Kempton, an early investigator of V2G technology since 1997, was initially convinced that this integration would become a commercial reality within a few years due to its apparent logic. However, nearly three decades later, V2G technology remains largely confined to a few experimental programs across the United States, Europe, Japan, and China.
A significant impediment to widespread adoption is the inherent complexity of reversing energy flow from the grid to the vehicle. Kempton points out that this requires fundamental shifts in how vehicle manufacturers, utility companies, and governments approach electric vehicles.
A primary technical hurdle lies in the differing electrical current types used by power grids and electric vehicles. Power grids predominantly operate on alternating current (AC), while most household appliances, including EVs, convert this AC to direct current (DC) for internal use when drawing power. For an EV to feed electricity back into the grid, this DC power must be converted back to AC.
Ensuring this conversion occurs safely, without risk of electrical shock, necessitates V2G components that meet stringent safety standards. Currently, the most straightforward method for implementing V2G involves installing a dedicated wall charger. These chargers convert DC to AC, adhering to established standards designed for solar panel integration. A few automotive manufacturers, such as Volkswagen and Nissan, have already introduced such chargers for use in specific markets.
However, the cost of these specialized wall chargers can run into thousands of dollars. In response, companies like Tesla, BYD, and Renault are developing EVs with integrated internal converters that handle the DC to AC transformation. Concurrently, Kempton and other researchers are working on new safety protocols for AC chargers. Kempton suggests that if this integrated technology becomes prevalent, it could enable V2G functionality with an added cost of only a few hundred dollars per vehicle.
The Format War Analogy and the Need for Standardization
The current landscape of V2G technology is characterized by a rivalry between DC-based V2G, exemplified by Volkswagen’s approach, and AC-based V2G, as pursued by Tesla. Alex Schoch, from the UK electricity retailer Octopus Energy, draws a parallel to the VHS versus Betamax videotape format war of the 1980s. While DC chargers, akin to Betamax, offer superior efficiency, AC chargers, comparable to VHS, are significantly more affordable. Historically, the cheaper and more accessible format, VHS, ultimately dominated the market.
Schoch’s perspective is that while the market can initially accommodate dual standards, achieving mass-market adoption requires alignment on a single format. Octopus Energy, he states, is a strong proponent of the AC standard.
For drivers to consider the additional expenditure of a few hundred dollars for V2G capabilities, a compensatory buyback tariff is essential. This tariff would remunerate them for supplying energy to the grid. Octopus Energy launched the UK’s inaugural V2G tariff in 2024, though its current accessibility is limited to a small number of car owners. To broaden this access, the company has partnered with BYD to offer a leasing option that includes a charger and an electric vehicle equipped for AC V2G.
Schoch anticipates that a substantial number of future EVs will be V2G-capable, either from their initial release or through upcoming models. He predicts this will result in the widespread availability of gigawatts of distributed grid storage capacity across countries.
Grid Infrastructure Challenges with V2G Expansion
The widespread adoption of V2G technology holds the potential to dynamically balance supply and demand on the power grid. However, as an increasing number of EVs with V2G chargers connect to the network, this will inevitably place greater strain on existing electrical infrastructure. Consequently, V2G deployment is likely to necessitate significant upgrades to national power grids.
A recent study indicated that a coordinated, comprehensive upgrade of national power grids would be more cost-effective than incremental improvements made as V2G capacity grows. Liangcai Xu, the lead author of the study from the National University of Singapore, advises that nations should prepare their power systems at a very early stage for the impending V2G revolution.
Co-author Ziyou Song, also from the National University of Singapore, expressed surprise at the findings. While initially believing V2G could be a comprehensive solution, the study revealed a substantial gap. Song concluded that power systems require significant upgrades to effectively accommodate the projected increase in electrical charging demand.