ISO 15118 plug-and-charge

ISO 15118 is a family of standards for digital communication between an EV and charging equipment. It can carry charging limits and schedules, support certificate-based identification and, in the newer generation, exchange the information needed for bidirectional power transfer.

Plug & Charge is one ISO 15118 use case, not another name for the whole standard. It allows a compatible vehicle to identify a charging contract and authorise a session through the cable, without the driver presenting an RFID card, bank card or charging app at the unit.

What happens when Plug & Charge works

The vehicle holds a contract certificate associated with an e-mobility service. When it connects to compatible charging equipment, the vehicle and charging system exchange and validate certificate information. The operator’s back-end authorises the contract and attributes the charging session to the account for billing.

Public key infrastructure provides the chain of trust behind those certificates. It deals with issuing, installing, renewing and revoking certificates and with establishing which certificate authorities the participants trust.

This means Plug & Charge depends on more than the socket and cable. The working chain includes:

• vehicle hardware and software implementing the relevant ISO 15118 functions
• charging equipment implementing the same compatible functions
• a valid contract certificate in the vehicle
• a back-end able to process ISO 15118 certificate and authorisation messages
• compatible trust infrastructure and commercial agreements

If any part is missing, the charger may still charge the car using an app, RFID card, contactless payment or another authorisation method. It is the automatic certificate-based route that fails, not necessarily the ability to transfer energy.

Vehicle-to-charger and charger-to-back-end are different links

ISO 15118 governs communication between the vehicle and the EV supply equipment. OCPP usually governs the separate connection between the charge point and its management system.

They need to work together for a networked Plug & Charge service, but one does not prove the other:

• ISO 15118 support in the charger does not confirm that its back-end can manage the certificates
• OCPP support does not confirm that the vehicle-facing ISO 15118 function is present
• a physical Type 2 or CCS connection does not, by itself, establish high-level communication support

OCPP 2.0.1 includes native support for ISO 15118 Plug & Charge, but the Open Charge Alliance certification scheme treats ISO 15118 support as an optional profile. An OCPP 2.0.1 certificate therefore needs to be checked for that profile rather than read as automatic proof.

The Open Charge Alliance also published a route for handling Plug & Charge over OCPP 1.6 using its DataTransfer mechanism. It describes this as an intermediate solution. ISO 15118 smart-charging functions need OCPP 2.0.1 under that guidance, while OCPP 2.1 adds support for ISO 15118-20 and bidirectional power transfer.

The two application-layer generations

The two references most often encountered are ISO 15118-2 and ISO 15118-20.

ISO 15118-2:2014 defines first-generation network and application-layer communication for energy transfer from the charger to the vehicle. It includes the data model and use of technologies such as TLS, TCP, IPv6 and XML/EXI data representation. ISO confirmed this edition in 2024, so it remains current as at 22 July 2026, but ISO also marks it “to be revised” and has a replacement draft in development.

ISO 15118-20:2022 is the second-generation network and application-layer standard. It includes communication for bidirectional power transfer and covers additional communication arrangements, including wireless communication and automatic connection devices.

ISO published Amendment 1:2026 to Part 20 on 13 July 2026. Its stated scope adds an AC distributed-energy-resource service, a Megawatt Charging System service and an improved security concept. A claim of current Part 20 compliance should therefore state whether the amendment is included.

The generations should not be treated as a feature switch that any older charger can gain by changing one setting. Compatibility depends on the implemented protocol stack, hardware, firmware, conformance and back-end. Ask for the exact part, amendment and supported use cases.

Plug & Charge is not the same as automatic recognition

Some networks start a session automatically by recognising another vehicle identifier. A proprietary “autocharge” feature can feel similar to the driver because plugging in is the only visible action.

The distinction is how identity and trust are established. ISO 15118 Plug & Charge uses the contract-certificate and public-key-infrastructure model. A network-specific automatic-start service may use a different identifier and work only with that operator. The words “automatic charging” or “plug and charge” in general marketing copy are not enough to prove ISO 15118 implementation.

Look for an explicit reference to ISO 15118 Plug & Charge and evidence that the function is enabled for the exact vehicle, market, software version, charge point and service contract.

Smart charging and state-of-charge data

ISO 15118 can exchange richer charging information than the basic signalling used to establish that an EV is connected and the current available to it. That creates a route for negotiating charging schedules and other limits between vehicle and charger.

It does not follow that every ISO 15118-capable vehicle exposes battery state of charge to every home charger. Support can differ between AC and DC charging and between software versions. The charger’s app may also depend on its back-end receiving and displaying the relevant message.

A complete data path requires:

1. vehicle support for the required ISO 15118 function on the charging method in use
2. charger implementation of that function and access to the result
3. a local energy-management system or cloud platform able to use it
4. defined behaviour if the internet or manufacturer’s service is unavailable

Without that complete path, “ISO 15118 ready” does not establish working state-of-charge-based control.

Bidirectional charging

ISO 15118-20 defines the communication messages and sequence requirements for bidirectional power transfer. This is necessary communication infrastructure for vehicle-to-grid or vehicle-to-home systems, but it is not the entire system.

Actual export also depends on:

• bidirectional power electronics in the vehicle and charging equipment
• a mutually supported charging mode
• installation design and protective equipment
• DNO connection requirements
• metering, tariff and service arrangements
• backup isolation and changeover design where the home can run during a power cut

A vehicle or charger listing ISO 15118-20 is therefore not, by itself, proof that bidirectional operation is enabled or approved in a particular UK installation.

UK regulatory position

The Great Britain EVs (Smart Charge Points) Regulations require covered private chargers to have smart functionality and meet requirements for supplier switching, loss of communications, default control, information and security.

The government guidance does not name ISO 15118 as the mandatory way to meet those duties. A product can comply with the UK smart-charge-point rules without offering Plug & Charge, and ISO 15118 support does not on its own prove compliance with all of those product rules.

No official UK timetable establishes that a foreign regulatory requirement will make an existing vehicle and charger combination interoperable. UK operation depends on actual vehicle, chargepoint, service and back-end support.

Vehicle, chargepoint and contract support

Interoperability depends on:

• the supported ISO 15118 part and amendment
• whether support is on AC charging, DC charging or both
• whether Plug & Charge is implemented, tested and enabled
• which vehicles and software versions have been interoperably tested
• how the contract certificate is installed and renewed
• which mobility services and trust infrastructure are supported
• the OCPP version and whether the ISO 15118 profile is included
• whether state of charge is available to local or cloud controls
• what bidirectional functions, if any, are enabled in the UK

The exact answers matter more than a general ISO 15118 logo or “future-ready” claim.

Related entries

• EVs Smart Charge Points Regulations
• OCPP charger control
• Vehicle-to-home backup charging
• Vehicle-to-home storage overlap
• CCS rapid charging
• Type 2 connector
• Smart charging schedules
• EV chargepoint commissioning