Your car as a mobile battery: how V2G powers the grid

Cars spend about 95% of their lifetime parked. Electric vehicles (EVs) are no exception. Under their hoods, there is also a battery – notably their most expensive component – which, most of the time, does nothing. Vehicle-to-grid (V2G) technology starts from a question: what if that stored energy could flow out, powering a home or supporting the grid rather than staying idle? 

The idea of using EV batteries as an integral part of the electricity grid has been around for a decade now — and Europe is at the forefront of the technology development. Let’s dive into it.  

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What is V2G? 

V2G is the technology that enables energy stored in an EV battery to be fed back into the electricity grid. EV batteries act as backup power for the electrical grid when needed. In turn, EV owners receive compensation for giving their power back to the grid. V2G falls under an umbrella of technologies known as V2X (vehicle-to-everything), where the energy stored in an EV battery can serve multiple purposes. 

How does V2G work? 

A V2G setup uses bidirectional EV charging stations to draw and feed energy back to the electricity grid. Standard EV charging routes electricity from the grid through your charger into your car’s battery. V2G can invert this path. 

When connected to a bidirectional charger linked to a V2G program, the charger's inverter converts the direct current (DC) stored in the battery pack into AC power that matches the grid’s frequency. Power then flows from your electrical panel and meter to the grid. 

However, there are three elements needed to make this system work: 

1. Your car must be V2G capable. Not all EVs are built with this feature, which essentially consists of both hardware and software to support bidirectional power flow. 
2. A bidirectional charger capable of converting power from and to the vehicle. 
3. Enrollment in a V2G program. Having a car and a charger that support V2G is not enough; a link to the electricity grid is the key. A V2G program does that, coordinating when your vehicle discharges electricity and how you are compensated. The EV battery management system (BMS) must be programmed to enable discharging and to communicate with the external charger using the appropriate protocols. 

Once these three elements are in place, an EV can do different things: power a home during a blackout, support a building’s electrical load, or simply sell electricity back to the grid when demand and prices are highest. 

What are the pros of V2G? 

• A giant, distributed battery for the grid. Electric grids need flexibility to absorb the rise of intermittent renewables like wind and solar. Parked EVs represent enormous storage capacity that already exists — no new batteries need to be built. The International Energy Agency has flagged V2G as offering some of the largest hourly energy flexibility of any technology it has evaluated, with the potential to reduce the need for new grid investment.
• Extra income for EV owners. Owners can be paid for feeding electricity back during peak demand, or for simply making their battery available to help balance the grid. Commercial offers launching in 2026, such as Volkswagen's V2G platform with its energy brand Elli, are built explicitly around this: charge cheaply, discharge profitably.
• Backup power. A bidirectional EV can act as a home battery during an outage, an appeal that's driving interest from utilities like Michigan's DTE Energy, which is piloting EV-based backup power with General Motors.
• Fleet economics. For fleets that sit unused for long periods — such as school buses or rental trucks — V2G turns dead time into a revenue stream, helping offset the higher upfront cost of electrifying a fleet.

What are the cons of V2G?

• Hardware isn't ready everywhere. Many existing chargers run on low-cost microcontrollers that simply cannot support the newer bidirectional standard without a hardware overhaul, not just a software update. Early UK type-testing of bidirectional chargers has seen a notably high failure rate, a sign the technology works in principle but isn't yet plug-and-play.
• Battery wear concerns. Extra charge-discharge cycling could, in theory, accelerate battery degradation, although smart V2G systems are designed to keep batteries within a moderate state-of-charge range specifically to limit this effect. Long-term, real-world data on this is still accumulating.
• Regulatory fragmentation. Rules on tariffs, grid fees, and who counts as an "energy aggregator" vary hugely by country, and in some places — Germany, until recently — bidirectional charging was effectively taxed twice, once for electricity in and once for electricity out.
• Interoperability is still maturing. Getting a car from one manufacturer to reliably talk to a charger from another, using an open standard rather than a proprietary one, has only recently been independently verified for the first time.

Where does the technology stand now?

Europe is leading the charge. France, the Netherlands, and the UK now have the regulatory conditions in place for commercial V2G, and Germany scrapped double grid fees for bidirectional charge points at the end of 2025.

Renault has run one of Europe's most closely watched V2G experiments. It started in Utrecht with "Utrecht Energized." The automaker supplied electric Renault 5 E-Tech and Renault 4 E-Tech models fitted with its Mobilize V2G toolkit, which were used as shared vehicles that charged when renewable energy was abundant and fed power back into the local grid during peak demand. Grid operator Stedin reported that over five months, 50 of these cars reduced evening grid congestion by up to 300 kW and fed more than 65,000 kWh back into the grid, prompting MyWheels to scale the fleet toward hundreds of V2G-capable vehicles. Eindhoven has also been hosting the experiment. 

In the United States, momentum is concentrated in fleets rather than private cars. The Department of Energy has funded fourteen V2G pilots nationwide using electric school buses, and utilities including ComEd in Illinois and PG&E in California have launched their own pilots — the latter upgrading a school district's entire electrical infrastructure to handle two-way power flows. GM says it already has over 250,000 bidirectional-capable vehicles on American roads.

Powering up, slowly

V2G is moving the first concrete steps. But the gap between marketing announcements and dependable, interoperable hardware is still real, and closing it will take a few more years of work on chips, certification, and tariffs. 

As EV adoption keeps growing, the potential of V2G to strengthen the electricity grid will improve accordingly. Analysts estimate that by 2050, there will be 11 million electric passenger cars and 1.2 million vans on Dutch streets — or 12.2 million batteries if you prefer. The potential for capillary storage, right where it is needed, is huge. 

If the further technology development needed to optimize the technology pays off, the EV in your driveway may end up doing double duty: getting you to work, and quietly helping keep the lights on.