Guide · ISO 15118 explained
ISO 15118: how electric vehicle and charging station communicate
What ISO 15118 regulates, how the parts -2 and -20 differ, what Plug & Charge needs and which ISO 15118 obligations AFIR sets for charging points from 2026 and 2027 – and how conformance, analysis and interoperability are tested with EVCA and comframe.
What is ISO 15118? The short answer
ISO 15118 is the international standard series for digital communication between an electric vehicle and a charging station. Its official title is “Road vehicles – Vehicle to grid communication interface”. On the vehicle side, the EVCC (Electric Vehicle Communication Controller) communicates; on the charging-station side, the SECC (Supply Equipment Communication Controller).
IEC 61851-1 only signals a few states and the maximum current via a PWM signal on the control pilot (CP). ISO 15118 adds a full data exchange: vehicle and charging station agree on energy demand, limits and charging schedule, authorise the charging contract and – with ISO 15118-20 – also control bidirectional charging.
ISO 15118 makes possible:
- Plug & Charge: the vehicle authorises itself with a certificate – no card, no app.
- Smart charging: charging power and schedule follow the limits the charging station passes on, for example from the grid or the tariff.
- Bidirectional charging: with ISO 15118-20 the vehicle can also feed energy back.
- Secure communication: TLS encryption, mandatory in ISO 15118-20.
For conductive AC and CCS charging, the data runs as power line communication (PLC) over the CP line – there is no extra wire in the cable. The Megawatt Charging System (MCS) uses single-pair Ethernet instead; a separate part covers wireless communication.
The parts of ISO 15118 at a glance
The series is split into requirement parts and conformance-test parts. These are the parts that matter most for vehicle and charging-station tests:
| Part | Content | Role in practice |
|---|---|---|
| ISO 15118-1 | General information and use-case definition | Terms and use cases for all other parts |
| ISO 15118-2 | Network and application protocol requirements (1st generation) | Charging sequence and Plug & Charge with TLS; required by AFIR since 2026 |
| ISO 15118-3 | Physical and data link layer requirements | PLC (HomePlug Green PHY) on the CP line, including connection set-up (SLAC) |
| ISO 15118-4 | Network and application protocol conformance test | Test cases for implementations of part 2; as SECC Test Library in comframe |
| ISO 15118-5 | Physical and data link layer conformance test | Test cases for implementations of part 3; as SECC Test Library in comframe |
| ISO 15118-8 | Physical and data link layer requirements for wireless communication | Wireless data link |
| ISO 15118-10 | Physical and data link layer requirements for single-pair Ethernet (2025) | 10BASE-T1S, for example for MCS |
| ISO 15118-20 | 2nd generation network and application layer requirements (2022; Amendment 1: 2026) | AC, DC, wireless and automated connection; bidirectional charging; required by AFIR from 2027 |
| ISO 15118-21 | Conformance test plan for the common requirements of part 20 (2025) | Abstract test suite for EVCC and SECC |
The table shows the parts relevant to charging tests; the ISO catalogue lists all parts and current editions. AFIR refers to the European editions (EN ISO 15118).
DIN 70121, ISO 15118-2 and ISO 15118-20 compared
Three protocol generations meet at today’s DC charging points. At the start of every session, vehicle and charging station agree on the protocol both support – many charging stations therefore implement several of them.
| Aspect | DIN 70121 | ISO 15118-2 | ISO 15118-20 |
|---|---|---|---|
| Charging types | DC only | AC and DC | AC, DC, wireless and automated connection |
| Encryption (TLS) | none | optional; required for Plug & Charge | mandatory (TLS 1.3) |
| Plug & Charge | no | yes | yes |
| Bidirectional charging | no | no | yes |
| AFIR | – | from 8 January 2026 (public charging points) | from 1 January 2027 (public and private charging points) |
DIN 70121 was the German specification for DC charging communication before ISO 15118-2. Older vehicles still use it, so charging stations keep it as a fallback. CharIN expects ISO 15118-2 and the older protocols to remain in use alongside ISO 15118-20 until at least 2028.
Plug & Charge: how automatic authorisation works
With Plug & Charge, the charging contract sits in the vehicle as a contract certificate. When the cable is plugged in, vehicle and charging station set up an encrypted TLS connection, the vehicle presents its certificate and the charging station checks it against the issuing certificate chain. If the check succeeds, charging starts – without an RFID card or app.
The alternative is external identification means (EIM): the driver identifies at the charging station, for example with an RFID card or an app; ISO 15118 then handles the charging sequence only.
Typical faults in Plug & Charge tests are an expired certificate, a missing root certificate in the charging station and a wrong system time on one side. A meaningful test therefore records the certificate status and device time together with the messages. In EVCA ComOnly, the certificate and security context is configurable for supported ISO 15118 charging profiles.
From 1 January 2027, AFIR requires publicly accessible charging points that offer automatic authentication such as Plug & Charge to support both ISO 15118-2 and ISO 15118-20.
What AFIR requires for ISO 15118
The EU Alternative Fuels Infrastructure Regulation (AFIR) makes ISO 15118 mandatory in steps. The technical details are set out in Delegated Regulation (EU) 2025/656. The obligations apply to charging points that are newly installed or renovated from the respective date; “renovated” means a major or complete replacement of the charging-point equipment.
| From | Charging points (newly installed or renovated) | Requirement |
|---|---|---|
| 8 January 2026 | Publicly accessible AC and DC charging points | At least EN ISO 15118-1, -2, -3, -4 and -5 |
| 1 January 2027 | Publicly accessible charging points | At least EN ISO 15118-20:2022; with automatic authentication such as Plug & Charge, both ISO 15118-2 and ISO 15118-20 |
| 1 January 2027 | Charging points that are not publicly accessible (Mode 3 and Mode 4) | At least EN ISO 15118-20:2022 |
The 2027 date is debated: in April 2026, CharIN recommended phasing in ISO 15118-20 and postponing the mandatory date until compliant solutions are mature. As far as we know (October 2026), 1 January 2027 still applies. This is engineering information, not legal advice. More context: AFIR: charging access, payment and technical requirements.
How ISO 15118 is tested: conformance, analysis and interoperability
ISO 15118 testing answers four different questions – from one implementation against the standard to a real vehicle at a real charging station. In the laboratory, comemso covers all four with the EV Charging Analyzer (EVCA) and the test software comframe: EVCA simulates the vehicle or the charging station, records communication and power on one timeline and checks both against the standard.
| Test task | Question it answers | EVCA and comframe |
|---|---|---|
| Conformance | Does one implementation – the SECC of a charging station or the EVCC of a vehicle – pass the standardised test cases? The cases come from ISO 15118-4 and -5 for the first generation and from ISO 15118-21 for ISO 15118-20. | Conformance Test Libraries in comframe: the ISO 15118-4/-5 SECC Test Libraries for AC and DC charging stations are released, with PICS/PIXIT configuration and a report for each test case. CharIN lists comemso as a validated Conformance Test System vendor for the Basic and Extended DC EVSE profiles. |
| Protocol analysis | Where does a recorded charging session deviate from the standard? | Automated Standards Analysis compares messages, state transitions and timing with the configured DIN 70121 and ISO 15118 requirements and highlights deviations; for ISO 15118-2 and -3 it lines up high-level communication with PLC and low-level timing. It supports, but does not replace, a formal conformance test. |
| Robustness | How does the device react when the partner behaves at the limit or does not conform? | Professional Simulation in EVCA ComOnly and EVCA Flex varies values, message availability, timing and sequence – for CCS with valid or invalid DIN 70121 and ISO 15118-2 parameters within the XML schema ranges. ComOnly tests the charging controller before the power hardware exists. |
| Interoperability | Why do a specific vehicle and a specific charging station not work together? | EVCA Interop sits between the real vehicle and the real station and, depending on the configuration, records PLC, SLAC and high-level communication, CP/PP signals, voltage and current on one timeline. Manipulating Gateway changes ISO 15118 messages while both partners stay connected; Charge Playback brings the recorded partner back into the laboratory (in CANoe today, in comframe planned for Q1/2027). |
The four tasks build on each other: a conformance verdict shows that one implementation passes the test cases, but it does not guarantee that two implementations work together. That is why interoperability is also tested with real partners – in the laboratory and at industry events such as the CharIN Testivals. Planning a test? Interoperability & charging analysis describes the method; the Product Finder suggests the matching EVCA system.
Communication check at commissioning
At the installed charging point, the test checks whether the charging station sets up the PLC connection and runs the communication sequence correctly. A conspicuously high attenuation during connection set-up points to an impaired signal path.
Easy Chester Micro tests AC charging points to ISO 15118-2 with EIM authentication; Easy Chester Ultimate does so for AC and DC. The ISO 15118-20 extension is planned for the first quarter of 2027 for both. The step-by-step field test is described in the guide Testing a wallbox; Plug & Charge and bidirectional cases in ISO 15118-20: Plug & Charge and BPT tests.
Frequently asked questions about ISO 15118
Is ISO 15118 mandatory?
In the EU, for newly installed or renovated charging points: for publicly accessible charging points since 8 January 2026 (parts 1 to 5), and from 1 January 2027 ISO 15118-20 for publicly accessible and private charging points. The legal basis is AFIR with Delegated Regulation (EU) 2025/656.
What is the difference between ISO 15118 and OCPP?
ISO 15118 covers communication between the vehicle and the charging station. OCPP (Open Charge Point Protocol) covers communication between the charging station and the operator’s backend. Plug & Charge needs both: the charging station exchanges certificate data with the vehicle via ISO 15118 and with the backend via OCPP.
What is the difference between ISO 15118 and IEC 61851?
IEC 61851-1 defines the basic signalling on the control pilot: PWM signal, states and maximum current. ISO 15118 builds on it and adds the digital data exchange for charging parameters, authentication and charging schedules.
Does ISO 15118 need a different cable or connector?
No. For AC and CCS charging, the PLC signal runs on the existing control pilot line of the Type 2 or CCS connector. MCS uses single-pair Ethernet in the MCS connector.
Sources
Regulation:
Commission Delegated Regulation (EU) 2025/656, Annex (AFIR technical specifications), EUR-Lex
Standards (ISO catalogue):
ISO 15118-10:2025 – single-pair Ethernet
ISO 15118-21:2025 – conformance test plan for ISO 15118-20
Industry and research:
CharIN: Position paper clarifying ISO 15118 implementation under AFIR, 28 April 2026
Technical content: comemso. Updated . German version: ISO 15118 erklärt.