Electric cars could make their owners money while they sit idle
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At least 90 percent of the electricity generation being built today is renewable. But solar and wind farms only produce electricity when the sun is shining and the wind is blowing, so the supply of electricity will fluctuate more. A pilot project in the US state of Delaware has shown that electric vehicle (EV) owners could make thousands of dollars each year by allowing their parked cars to serve as part of a giant collective battery that stores electricity when supply is high and distributes it when demand is high.
Some data suggest that the average EV is driving only 5 percent of the time. Otherwise, it is often parked and plugged in. That means instead of building giant battery farms, electric companies could balance the grid by taking power from these cars when usage peaks in the morning and evening and then recharging them during the day, he says. Willett Kempton at the University of Delaware, which he led project. EV owners could sell electricity at a premium while saving money for the grid.
“An electric car plugged in 95 percent of the time it’s not driving can provide storage for the grid at about a tenth of the cost of building batteries,” says Kempton. “[That could] to help increase the reliability of any electricity system and increase our ability to bring more and more renewables into the system.”
As part of the project, four Ford electric vehicles owned by Delmarva Power were retrofitted to feed electricity back into the power system through vehicle-to-grid (V2G) charging. Kempton and his colleagues monitored their V2G charging throughout the year 2025. Given the amount of electricity the cars fed into the grid, each electric car could earn up to $3,359 a year if that energy were sold at market price.
When Kempton became one of the first to explore V2G in 1997, it made so much sense that he thought it would become a commercial reality within a few years. But nearly 30 years later, V2G largely exists in a few test programs in the US, Europe, Japan and China.
The main reason is that reversing the flow of power from the grid to the car is proving surprisingly complex, requiring vehicle manufacturers, energy companies and governments to change the way they approach EVs, Kempton says.
The biggest problem is that power grids run largely or exclusively on alternating current (AC), while most home appliances, including electric cars, convert that alternating current to direct current (DC) when they draw power from the outlet. In order for an electric car to supply the grid, the energy must be converted back into alternating current.
To do this without electrocution requires V2G components to be manufactured to safety standards. The easiest way to set up V2G these days is to install a wall charger that converts DC to AC according to standards designed to allow solar panels to feed into the grid. Several automakers, including Volkswagen and Nissan, offer wall chargers that do this in some markets.
But these wall chargers can cost thousands of dollars. So companies including Tesla, BYD and Renault have begun developing electric cars that convert DC to AC inside the car itself, and Kempton and others are working on new safety standards for AC chargers. If the technology becomes widespread, it could enable V2G while adding just a few hundred dollars to the price of the car, Kempton says.
Currently, there is a rivalry between DC V2G like Volkswagen and AC V2G like Tesla. It’s similar to the format war between VHS and Betamax videotapes in the 80’s. Alex Schoch at the British electricity retailer Octopus Energy. Betamax offered better quality, similar to DC chargers that are more efficient. But VHS players were much cheaper, as were AC chargers, and VHS eventually dominated the market.
“Our view is that there is a period where the market can deal with two different standards, but to really scale and get to the mass market, you have to adapt to one,” says Shoch. “We are firmly team… AC.
But for drivers to want to spend even an extra few hundred dollars to set up V2G, there needs to be a feed-in tariff that allows them to earn money by feeding power into the grid. In 2024, Octopus launched the UK’s first V2G tariff, although there are still few car owners who can use it. To this end, it has also partnered with BYD to allow consumers to rent a charger and electric vehicle equipped for AC V2G.
“Many manufacturers, the electric cars they put on the road are V2G capable, or the next generation that will hit the road today or tomorrow,” says Schoch. “And you [will] suddenly they have gigawatts of capacity that is distributed across the country.”
The adoption of V2G could help balance demand and supply in the network in real time. But once more electric cars with V2G chargers start connecting, it will also put more strain on the existing electrical system. As a result, V2G is likely to force countries to upgrade their power grids.
Recent studies It has been calculated that it would be more cost-effective for countries to upgrade their networks all at once, rather than upgrading them gradually as V2G increases gradually. According to the study’s lead author, states should “prepare the energy system at a very early stage” for the coming V2G revolution, Liangcai Xu at the National University of Singapore.
“I was surprised because I thought V2G could be a silver bullet, it could solve everything,” says co-author Ziyou Song, also at the National University of Singapore. “[But] the gap is quite significant. We need to properly modernize our energy system [so] we can facilitate so much demand for electric charging.”
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