Vehicle-to-grid

Also known as V2G, Vehicle to grid, Bidirectional charging

Vehicle-to-grid (V2G) lets an electric car send power from its battery back to a home or the grid, not only take power in. A few UK and Dutch schemes are running, but the evidence on whether discharging speeds up battery wear is mixed, and most of it comes from lab cells or simulations.

Pilot and early commercialReported, unverifiedReviewed 21 Oct 2026
AI illustration · Illustrative scene, not a photograph of the specific device or experiment.

In plain language

An electric car battery is normally only filled. Vehicle-to-grid, or V2G, adds the reverse direction: the battery can also feed electricity back through a bidirectional charger into the home or the wider grid. The idea is that many parked cars could together act as a store of power, charging when electricity is cheap and plentiful and releasing it when demand is high.

To do this, three things have to work together: a car that can discharge, a charger that can convert power in both directions, and a way for the car, the charger and an energy company to communicate. Early schemes in the UK offer owners a discount or a free-charging bundle in return for letting the operator decide when the car charges and discharges. The open questions are whether owners will accept the extra wear on their battery, and whether the payments are large enough to matter.

Technical explanation

A bidirectional charger converts power between the grid's alternating current and the battery's direct current in both directions. V2G therefore needs both a charger and a vehicle that support bidirectional power flow, and the two must exchange messages to agree on how much power to move and when. ISO 15118-20:2022 is the second-generation standard for this communication. It specifies the messages and their sequence for bidirectional power transfer between battery electric or plug-in hybrid vehicles and the supply equipment, and it covers wireless as well as conductive charging.

Battery wear is the central technical question. Discharging adds charge and discharge cycles and can change how deeply and how often the battery is cycled. A University of Hawaii study on commercial lithium-ion cells reported faster capacity loss with daily V2G cycling. A 2021 simulation study from the University of Warwick reported that charging strategies which set the state of charge before V2G operation did not speed up ageing and reduced total ageing. These studies use different cells, protocols and models, so their results cannot be compared directly, and neither measures how a real car ages in everyday use.

The value of V2G depends on the services a car can provide, such as export at times of peak demand, balancing and local network support. The UK Vehicle to Grid Britain (V2GB) project modelled residential V2G and found that income depended heavily on plug-in patterns, metering costs and the ability to combine revenue streams. The Utrecht Energized car-sharing scheme, which uses bidirectional Renault 5 vehicles, has been reported as live, but no measured grid-service volumes were published in the sources reviewed.

What the evidence says

Each statement is typed by the strength of its evidence and linked to the source that supports it.

Demonstrated Shown in a published experiment, test or shipping product.

Octopus Power Pack is offered in the UK as a V2G tariff, and its page lists one qualifying combination: a V2G-enabled BYD Dolphin with a V2G-enabled Zaptec Pro charger.

Sources: [1] · Eligibility section

Octopus Power Pack requires the vehicle to be plugged in for 12 hours a day on 20 days a month, with charging under 210 kWh a month, a smart electricity meter and a G99 certificate for export to the local network.

Sources: [1] · Usage conditions section

ISO 15118-20:2022, published on 26 April 2022, specifies the communication messages and sequence for bidirectional power transfer between battery electric or plug-in hybrid vehicles and their supply equipment.

Sources: [7] · Scope

Reported, unverified Stated by a company or team but not independently confirmed.

Octopus says a typical V2G driver could save 620 pounds a year compared with Flexible Octopus, based on a customer driving 7,500 miles a year at 0.306 kWh per mile; the FAQ names a standard variable tariff as the comparison.

Sources: [1] · Header and FAQ · medium confidence

Utrecht Energized was reported live in June 2025 with 50 Renault 5 E-Tech vehicles, with a total of 500 V2G-capable vehicles planned, operated through a MyWheels car-sharing service with We Drive Solar supplying bidirectional public AC chargers.

Sources: [3] · Article body · medium confidence

The V2GB project found that residential V2G viability depended on high plug-in rates, lower costs for high-accuracy smart metering and stacking several revenue streams, and that a typical residential 7 kW charger earned about 100 pounds a year, with over 400 pounds only in ideal circumstances.

Sources: [4] · Key findings · medium confidence

In a University of Hawaii lab study on commercial cells, one V2G cycle a day raised capacity loss by 33% and resistance by 5%, and two cycles a day raised them by 75% and 10%.

Sources: [5] · Article body · medium confidence

In a semi-empirical simulation, Bui and colleagues reported that five state-of-charge pre-conditioning strategies did not accelerate degradation and reduced total ageing by 7.3% to 26.7% over the first 100 days, and by 8.6% to 12.3% over one year, compared with a standard charging reference.

Sources: [6] · Abstract · medium confidence

Proposed A design or plan that has not yet been built or tested.

A We Drive Solar release, as reported by pv magazine, said 500 bidirectional cars could provide 10% of the flexibility needed in the Utrecht region at peak times. This is a projection, and no measured figure was reported.

Sources: [2] · Article body · medium confidence

Limitations and open problems

  • The effect of V2G on battery life is not settled. Lab work on commercial cells reports faster capacity loss with daily discharging, while a simulation reports that managed charging reduces ageing; neither is a long-term field measurement of cars in normal use.
  • Most public evidence on UK and Dutch schemes is press coverage or project reporting. No measured grid-service volumes or customer uptake were found for the Utrecht scheme.
  • Octopus Power Pack's terms require a qualifying vehicle and charger, a smart meter, a G99 certificate for export to the local network, and regular plug-in hours. Its page lists one qualifying combination, which limits who can join.
  • Owner savings figures are company claims, and the comparison tariff is named inconsistently on the Octopus page.
  • The V2GB modelling found a typical residential 7 kW V2G charger earning about 100 pounds a year, and above 400 pounds only in ideal circumstances. Payback therefore depends on the charger cost and on the tariff.

Possible future uses

Speculative

Ideas, not predictions. None of these has been demonstrated.

  • Fleets of parked vehicles at workplaces or depots providing peak-time support to local networks.
  • Vehicle-to-home use, where a car supplies a house during a power cut.
  • Vehicle-to-building use in offices or shops to reduce peak electricity demand charges.

Product concepts: Car battery backup for a house during power cuts

Timeline

  1. 31 May 2017Charged EVs reports a University of Hawaii lab study in which daily V2G cycling of commercial cells sped capacity loss by 33%, and twice-daily cycling by 75%. Sources: [5]
  2. 1 Oct 2018The Vehicle to Grid Britain (V2GB) project page is published. The project page is later marked complete, and it reports the conditions under which residential V2G is viable. Sources: [4]
  3. 16 Nov 2021Bui and colleagues publish a simulation study in IEEE Access, reporting that state-of-charge pre-conditioning reduced total ageing by 7.3% to 26.7% over the first 100 days. Sources: [6]
  4. 26 Apr 2022ISO 15118-20:2022 is published, specifying communication for bidirectional power transfer between vehicles and supply equipment. Sources: [7]
  5. 28 Nov 2024pv magazine reports the Utrecht bidirectional car-sharing plan, with 500 Renault 5 vehicles and a projected 10% of regional flexibility needs. Sources: [2]
  6. 16 Jun 2025Utrecht Energized is reported live with 50 Renault 5 E-Tech vehicles, with 500 V2G-capable vehicles planned. Sources: [3]

Futures this could help bring about

AI illustration
How far away?

Electric cars that power the grid

Pilots · 2 of 9 steps done

Glossary

Bidirectional charger
A charger that can move power from the grid into a vehicle battery and back again.
State of charge
How full a battery is at a given moment, usually given as a percentage of its capacity.
Capacity loss
The reduction over time in the amount of charge a battery can store, sometimes called capacity fade.
Smart meter
An electricity meter that records use in detail and can communicate with the energy supplier, needed for time-varying tariffs.

Sources

  1. company announcement
    Octopus Power Pack
    Octopus Energy, 2026. Accessed 21 Oct 2026.
  2. news
    Utrecht to host vehicle-to-grid car sharing service
    Patrick Jowett. pv magazine, 28 Nov 2024. Accessed 21 Oct 2026.
  3. news
    Vehicle-to-Grid-enabled car-sharing service goes live in Netherlands city
    Charged EVs, 16 Jun 2025. Accessed 21 Oct 2026.
  4. other
    Vehicle-to-Grid GB: Decarbonising Britain
    Catapult Energy Systems, 1 Oct 2018. Accessed 21 Oct 2026.
  5. news
    New study finds V2G discharging harmful to EV batteries
    Charged EVs, 31 May 2017. Accessed 21 Oct 2026.
  6. peer reviewed paper
    A Study of Reduced Battery Degradation Through State-of-Charge Pre-Conditioning for Vehicle-to-Grid Operations
    Truong Minh Ngoc Bui, Muhammad Sheikh, Quang Truong Dinh et al.. IEEE Access, 16 Nov 2021. DOI: 10.1109/ACCESS.2021.3128774. Accessed 21 Oct 2026.
  7. standard
    Road vehicles - Vehicle to grid communication interface - Part 20: Network and application protocol requirements
    International Electrotechnical Commission (IEC) webstore, 26 Apr 2022. Accessed 21 Oct 2026.

Revision history

3 changes since this profile was created.

Changes on 21 Oct 2026
Published on owner instruction (content loop iteration 9)81096f5
Sources and claims re-checked against originalsfbb434c
Initial profile drafted from primary sources7e66249

What it took to get here

The inventions this technology was built on, oldest foundations at the top. Lines show what each one required.

Built on: Vehicle-to-grid Unlocked Being researched Locked
  1. 1856ManufacturingIndustrial steelmakingCommercial Unlocked.
  1. 1774ManufacturingPrecision machine tools and interchangeable partsCommercialRequires: Industrial steelmaking. Unlocked.
  1. 1967Modern systemsCar electronics and engine controlCommercial Unlocked.
  2. 3500 BCMovementThe wheel and axleCommercial Unlocked.
  3. 1712PowerThe steam engineCommercialRequires: Precision machine tools and interchangeable parts. Unlocked.
  4. 1859PowerLead-acid batteriesCommercial Unlocked.
  5. 1859PowerPetroleum refiningCommercial Unlocked.
  1. 1816ControlVehicle steeringCommercialRequires: The wheel and axle. Unlocked.
  2. 1827ControlClutches, gearboxes and differentialsCommercialRequires: Precision machine tools and interchangeable parts. Unlocked.
  3. 1902ControlVehicle brakesCommercialRequires: Car electronics and engine control. Unlocked.
  4. 1901ManufacturingAssembly-line mass productionCommercialRequires: Precision machine tools and interchangeable parts. Unlocked.
  5. 1952Modern systemsVehicle safety systemsCommercial Unlocked.
  6. 1956Modern systemsCatalytic convertersCommercial Unlocked.
  7. 1964Modern systemsSatellite navigation (GNSS)Commercial Unlocked.
  8. 1750MovementSprings and vehicle suspensionCommercialRequires: The wheel and axle. Unlocked.
  9. 1794MovementRolling bearingsCommercialRequires: Precision machine tools and interchangeable parts. Unlocked.
  10. 1844MovementVulcanised rubber and pneumatic tyresCommercialRequires: The wheel and axle. Unlocked.
  11. 1821PowerThe electric motorCommercialRequires: Industrial steelmaking. Unlocked.
  12. 1860PowerThe internal combustion engineCommercialRequires: The steam engine, Petroleum refining, Precision machine tools and interchangeable parts. Unlocked.
  13. 1976PowerLithium-ion batteriesCommercialRequires: Lead-acid batteries. Unlocked.
  1. 1769VehicleThe motor carCommercialRequires: The wheel and axle, Vulcanised rubber and pneumatic tyres, Springs and vehicle suspension, Rolling bearings, The internal combustion engine, The electric motor, Lead-acid batteries, Vehicle steering, Vehicle brakes, Clutches, gearboxes and differentials, Assembly-line mass production, Industrial steelmaking, Car electronics and engine control, Vehicle safety systems, Catalytic converters, Satellite navigation (GNSS), Lithium-ion batteries, Petroleum refining, Precision machine tools and interchangeable parts, The steam engine. Unlocked.
  1. 2017Vehicle-to-gridPilot and early commercialRequires: The motor car, Lithium-ion batteries. Unlocked.