Glossary

ISO 15118

An international standard defining the vehicle-to-grid communication interface for bidirectional charging, enabling secure digital certificate-based authentication known as Plug & Charge.

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V2G COMMUNICATION STANDARD

What is ISO 15118?

ISO 15118 is an international standard defining the digital communication interface between electric vehicles and the charging infrastructure, enabling secure, high-level data exchange for smart charging and bidirectional power transfer.

ISO 15118 is an international standard specifying the vehicle-to-grid (V2G) communication interface for bidirectional charging. It defines the digital handshake between an electric vehicle (EV) and the charging station, enabling advanced functions like Plug & Charge authentication, where the vehicle automatically identifies itself using encrypted digital certificates without requiring an RFID card or mobile app.

The standard's core mechanism relies on Transport Layer Security (TLS) encryption to establish a secure channel over power-line communication (PLC) or a wireless link. Beyond authentication, it facilitates smart charging by exchanging data on grid tariffs, energy schedules, and the vehicle's State of Charge (SoC), allowing the Charge Point Operator (CPO) to dynamically optimize power flow and enable Vehicle-to-Grid (V2G) energy export.

PLUG & CHARGE STANDARD

Key Features of ISO 15118

ISO 15118 defines the vehicle-to-grid (V2G) communication interface, enabling secure, automated authentication and bidirectional power flow between electric vehicles and charging infrastructure.

Plug & Charge (PnC)

An automated authentication mechanism that eliminates the need for RFID cards or mobile apps. The electric vehicle presents a digital certificate to the charging station upon physical connection, enabling instant, cryptographically secure identification and billing. This is governed by the ISO 15118-2 and ISO 15118-20 clauses on Transport Layer Security (TLS).

TLS 1.2+

Encryption Standard

X.509

Certificate Format

Bidirectional Power Transfer (V2G)

ISO 15118-20 specifies the communication protocols for Vehicle-to-Grid (V2G) energy transfer. It defines the message sequences for an EV to discharge stored battery energy back to the grid, supporting services like frequency regulation and peak shaving. The standard handles the complex handshake for power scheduling and grid code compliance.

ISO 15118-20

Governing Clause

Smart Charging (V1G) Scheduling

The standard enables dynamic control of the charging rate based on external signals from the grid operator. Using charge parameter discovery and power schedule messages, the EV and charge point negotiate an optimal charging profile that respects grid constraints, energy tariffs, and the driver's departure time without exporting power.

Dynamic

Power Modulation

High-Level Communication (HLC)

ISO 15118 mandates communication over a Power Line Communication (PLC) carrier, specifically HomePlug Green PHY. This transforms the charging cable into a secure IP-based data link. Unlike basic PWM control, HLC allows rich data exchange for certificate handling, value-added services, and complex energy management.

HomePlug GP

Physical Layer

Value-Added Services (VAS)

Beyond energy transfer, the protocol supports ancillary digital services. This includes wireless internet access for the vehicle, location-based services, and remote diagnostics. The standard defines a generic VAS interface allowing manufacturers to deploy proprietary applications over the established secure communication channel.

Public Key Infrastructure (PKI)

The security architecture relies on a hierarchical Public Key Infrastructure. A root Certificate Authority (CA) issues certificates to OEMs, which provision unique digital identities into vehicles during manufacturing. This chain of trust ensures that only authenticated EVs can initiate a Plug & Charge session, preventing fraud.

V2G PKI

Trust Model

ISO 15118 EXPLAINED

Frequently Asked Questions

Clear, technically precise answers to the most common questions about the international standard defining vehicle-to-grid communication and Plug & Charge authentication.

ISO 15118 is an international standard defining a digital communication interface between an electric vehicle (EV) and the charging infrastructure, specifically designed for bidirectional charging and automated authentication. It works by establishing a high-level communication protocol over power-line communication (PLC) or a wireless link, enabling the EV and the charging station to exchange complex data beyond basic power delivery. This includes negotiating charging schedules, exchanging digital certificates for the Plug & Charge mechanism, and managing bidirectional power flow for Vehicle-to-Grid (V2G) services. The standard specifies the use of Internet Protocol (IP)-based communication, with the EV acting as a client and the charging station as a server, ensuring a secure, encrypted tunnel for all transactions.

COMMUNICATION PROTOCOL COMPARISON

ISO 15118 vs. OCPP: Key Differences

A technical comparison of the communication scope, security architecture, and functional domains of ISO 15118 and the Open Charge Point Protocol.

Feature	ISO 15118	OCPP	Combined Use
Communication Endpoints	EV ↔ Charging Station	Charging Station ↔ Central System	End-to-end ecosystem
Primary Function	Bidirectional power control and authentication	Station management and remote monitoring	Full smart charging infrastructure
Plug & Charge (ISO 15118-2)
Bidirectional Power Flow (V2G)
Transport Layer Security	TLS 1.2+ with X.509 certificates	TLS 1.2+ (OCPP 2.0.1)	Layered security architecture
Authentication Method	Public Key Infrastructure (PKI)	Basic auth, token-based, or client certificates	Multi-factor across layers
Smart Charging Control	Direct load management via EV	Indirect via station profiles	Coordinated optimization
Firmware Update Management

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About the author

Prasad Kumkar

CEO & MD, Inference Systems

Prasad Kumkar is the CEO & MD of Inference Systems and writes about AI systems architecture, LLM infrastructure, model serving, evaluation, and production deployment. Over 5+ years, he has worked across computer vision models, L5 autonomous vehicle systems, and LLM research, with a focus on taking complex AI ideas into real-world engineering systems.

His work and writing cover AI systems, large language models, AI agents, multimodal systems, autonomous systems, inference optimization, RAG, evaluation, and production AI engineering.

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ISO 15118

What is ISO 15118?