ISO 15118-20:2022/AMD 1:2026 Clause-by-Clause Analysis: What Exactly Has Changed in Each Amendment?

ISO 15118-20 was officially published in 2022. In July 2026, ISO 15118-20 was revised to become ISO 15118-20:2022/AMD 1:2026.

Full title: "Road Vehicle-to-Network Communication Interfaces—Part 20: Second-Generation Network Layer and Application Layer Requirements—Amendment 1: AC DER Service, MCS Service, and Improved Security Concept (ISO 15118-20:2022/Amd 1:2026 Road vehicles — Vehicle-to-grid communication interface — Part 20: Second-generation network layer and application layer requirements — Amendment 1: AC DER service, MCS service, and improved security concept)

Judging by the title, this appears to be merely an “Amendment,” but if you actually read the entire amendment document, you’ll find that it is not a simple textual revision, but rather the first major update for industrial applications since ISO 15118-20 was published in 2022.

Why does an international standard that was published just a few years ago need to be revised? Does this mean that ISO 15118-20 is not yet fully developed?

The release of a standard does not mean that the industry is complete.

It is only when a standard is actually put into practical use that many issues that could not be detected during the laboratory phase gradually come to light. For example:

• Differences in how various companies interpret protocol implementation;
• Interoperability issues between different devices;
• Changes in demand in real-world energy service scenarios;
• Improvements to security and authentication mechanisms.

Therefore, international standards typically go through the following stages: development, publication, implementation, feedback, revision, and re-implementation. This is the natural progression of all mature technical systems.

What Changes Did ISO 15118-20 Amendment 1 Introduce?

Three new areas of focus:

• AC DER Service (AC Distributed Energy Resources Service)
• MCS Service (Megawatt-Class Charging System Service)
• Improved Security Concept (Enhanced Security Mechanisms)

The main difference between ISO 15118-20:2022 and Amendment 1:2026:

Part 1: Normative References—The Standards Framework Begins to Expand

Amendment 1 adds two new normative references:​

• ISO 15118-10:2025

• IEC 61851-23-3:2025​

This is the most easily overlooked yet most significant change in the entire amendment. ​While ISO 15118-20 was originally centered on PLC communication, ISO 15118-10 defines the physical and data link layer requirements for Single Pair Ethernet (10BASE-T1S); IEC 61851-23-3, for the first time, systematically specifies MCS DC charging equipment. ​In other words, from this point forward, ISO 15118-20 no longer serves only CCS but has officially expanded to support megawatt-class charging systems.​

Part 2: Over a Dozen New Terms Added—ISO 15118 Begins to Enter the Power Grid Domain

These include:​

• DER (Distributed Energy Resource)

• Area EPS​

• Enter Service​

• Return to Service​

• Ride-through​

• May Trip Region​

• Must Trip Region​

• Momentary Cessation Region

• Frequency Droop Curve, etc.

These terms share a common characteristic: most do not originate from the automotive industry, but rather from the field of grid interconnection control. This indicates that ISO 15118 has begun to incorporate control concepts from distributed energy standards such as IEEE 1547. In the past, vehicles were merely objects to be charged. In the future, vehicles will be viewed as energy resources capable of participating in grid frequency regulation, voltage regulation, and demand response. This is one of the most significant strategic changes introduced by Amendment 1.

Part 3: MCS Officially Becomes Part of ISO 15118. This section contains the most significant changes in the entire revision.

1. New MCS sleep mechanism added

2. Mandatory adoption of 10BASE-T1S:

3. No longer compatible with ISO 15118-2

Part 4: The PKI Security Framework Enters the Engineering Phase

This revision has essentially rewritten the entire OCSP and certificate validation process.

Key changes include:

First, new Requirements V2G20-3000 and 3001 have been added, stipulating that the validity period of all certificates must be fully contained within the validity period of the issuing certificate, and requiring that EVCCs and SECCs perform this check during validation.

Second, new recommendations regarding certificate size have been added.

Third, the OCSP validation logic has been comprehensively updated.

Multiple requirements—including those for SECC certificates, Vehicle Certificates, Contract Certificates, and OEM Provisioning Certificates—have been replaced. These updates require that OCSP signature certificates align with the corresponding Root CA and further standardize the trust relationships between different certificate chains.

Although these modifications do not directly affect application-layer messages, they will determine whether Plug & Charge can truly achieve global interoperability in the future.

Part 5: Stricter TLS Handshake Logic

Conditions for sending the `certificate_authorities` extension in `ClientHello`;

How `ServerHello` selects the certificate chain;

Different policies for Public SECC and Private SECC;

Further clarification of certificate request methods in `CertificateRequest`;

How EVCC automatically selects the most appropriate certificate chain based on the Distinguished Name.

All of these changes are aimed at a single goal: reducing interoperability issues during cross-Root CA deployments and improving compatibility between different PKI systems.

Part 6: AC DER Service—ISO 15118’s First Support for AC-Side Distributed Energy Services

Unlike the MCS, which introduces a large number of new communication requirements, the modifications related to AC DER primarily focus on building foundational capabilities. The goal is to enable ISO 15118 to support AC Distributed Energy Resource (AC DER) services, rather than to redesign an entirely new communication protocol. Unlike the traditional AC Charging Service, the AC DER Service no longer focuses solely on the charging process but rather on the information exchange capabilities required when a vehicle participates in AC grid operations as a distributed energy resource.

• New Requirements Related to DER Operational Status
• New Descriptions of DER Control Capabilities

What Does ISO 15118-20:2022/AMD 1:2026 Really Mean?

If we look at all the amendments together, we can see that they revolve around three key areas.

First, enabling ISO 15118 to support megawatt-level charging.

Second, to enable ISO 15118 to support new energy vehicles as distributed energy resources participating in grid operations.

Third, to ensure that Plug & Charge is truly capable of global commercial deployment.

Therefore, Amendment 1 formally incorporates the industry’s practical experience from the past few years into the international standard. For the first time, ISO 15118-20 truly possesses the capability to support MCS, V2G, and the global PKI ecosystem.​ This also means that, starting in 2026, the industry will truly enter the second-generation ecosystem development phase of ISO 15118. It marks a watershed moment for next-generation product architecture.