V2G charging

Exporting energy from a compatible EV through an approved bidirectional charging system.

V2G (vehicle-to-grid) charging allows energy stored in an EV battery to be exported through the property’s connection to the public electricity network. A control service may schedule that export in response to prices, network needs or another flexibility signal.

Ordinary smart charging is sometimes called V1G. It can vary when or how quickly the car charges, but the power flow remains from the electricity system to the vehicle. V2G adds reverse power flow and therefore needs compatible power electronics, control, protection and a permitted grid connection.

V2G, V2H and V2L are different

The labels describe where the vehicle’s energy can go:

V2L (vehicle-to-load) supplies appliances from an outlet or adaptor provided for that purpose.
V2H (vehicle-to-home) supplies loads within the property through a designed electrical connection.
V2B (vehicle-to-building) is the equivalent arrangement for a larger building.
V2G (vehicle-to-grid) allows controlled export through the grid connection.

A vehicle described as bidirectional may support only one of these uses. V2L does not prove that the vehicle can synchronise with a building or the grid. A portable output must never be connected to a socket to backfeed fixed wiring.

Where the conversion happens

The traction battery stores DC, while a grid-connected installation uses AC. The reverse conversion can be handled in two broad ways.

With DC bidirectional charging, the charger contains the grid-connected bidirectional inverter and communicates with the vehicle’s high-voltage battery system. With AC bidirectional charging, compatible power electronics in the vehicle export AC through charging equipment designed to control and protect that mode.

Neither route is automatically interchangeable with ordinary charging. The following must form a tested combination:

exact vehicle model, model year and software
charging equipment model and firmware
connector and charging mode
supported vehicle-to-charger communication functions
grid-interface type test and settings
chargepoint management or aggregation service, where required

The presence of CCS, Type 2, CHAdeMO or ISO 15118 in marketing material is not enough on its own. ISO 15118-20 provides communication for bidirectional power transfer, but it does not add reverse-capable power electronics, a grid approval or commercial service.

The grid connection is an embedded-generation connection

When a vehicle can export through the property, the bidirectional converter is generation equipment for connection purposes. Its route must be assessed under the current ENA engineering recommendations.

G98 may apply where the generating equipment, type-test evidence and registered capacity meet its requirements. Equipment outside that route requires a G99 application and permission before operation. Existing solar, battery storage or other generation must be included in the assessment. Installing a zero-export control does not remove the need to agree the connection route.

Where the DNO sets an export limit, a G100-compliant customer limitation scheme may be part of the approved design. That scheme controls the net flow at the connection point. It is different from an EV charger’s dynamic load control, which usually protects an import or site-current limit.

The handover documents retain the accepted application or notification, type-test record, single-line diagram, export settings and commissioning evidence.

Control and metering

A practical V2G service needs to know when the vehicle may charge or discharge and how much energy the driver wants to keep for travel. It may also need half-hourly import and export data, a compatible tariff or flexibility contract and access to the chargepoint through a back-end platform.

OCPP can carry instructions between a networked charger and its management system. ISO 15118 covers the separate link between vehicle and charging equipment. Support for one protocol does not prove support for the other, and a version number does not prove that every optional function is implemented.

The design should define what happens if the internet, cloud service, smart meter data or control platform is unavailable. A safe local limit and a usable charging fallback matter more than a promise that the unit is merely “smart”. Ownership of the charger account, credentials and historical data should be clear at handover.

Export does not mean power-cut backup

A grid-following V2G system normally disconnects when the public supply fails. That anti-islanding behaviour protects network workers and prevents an uncontrolled local island.

Supplying the home during an outage is a separate V2H backup function. It needs a compliant method of separating the installation from the grid, a source able to establish local voltage and frequency, suitable earthing and protection in island mode, and defined backup circuits or whole-home load management. A product able to export while the grid is present may have no outage capability at all.

Battery use and driving reserve

V2G makes the vehicle battery serve two jobs. A schedule that earns from export is of little use if it leaves too little energy for the next journey or the car is away when the service expects it to be connected.

The service configuration includes:

minimum state of charge and departure-time controls
whether the vehicle can override a dispatch request
the effect of cabin or battery preconditioning
conversion losses and the system’s standby consumption
how imported and exported energy is measured and settled
the vehicle battery warranty, lease terms and permitted bidirectional use
who is responsible if a software or tariff change removes compatibility

Extra cycling contributes to battery throughput, but there is no universal degradation percentage for V2G. Cell chemistry, temperature, state-of-charge window, power, calendar age and the control strategy all matter. A manufacturer-approved operating mode and explicit warranty position are more meaningful than a generic cycle-life estimate.

Assessing the value

V2G value is not a fixed annual saving. It depends on the difference between import and export value, conversion losses, time plugged in, energy reserved for driving, service fees, hardware and installation costs, and any effect on the vehicle contract or battery.

Tariffs, supported vehicle-and-charger combinations and service rules change too quickly for a permanent compatibility table to stay reliable. The applicable provider terms define the service and vehicle combination. Any financial forecast needs stated prices, plug-in availability, energy throughput and equipment life rather than one typical payback period.

Compatibility and service boundaries

Working V2G depends on:

support for the exact UK vehicle and software, not only a “ready” description
a tested charger and vehicle combination
the required UK grid-interface evidence
a DNO route covering existing and proposed generation
coordination between export limitation, solar and battery controls
acceptance of the vehicle, charger and meter arrangement by the tariff or aggregator
safe, usable charging after a loss of communications
vehicle warranty or lease terms that permit the intended cycling
a separately designed outage-backup system where required

Applies to

EV charging, Battery

Last reviewed

22 Jul 2026