ISO 15118-20 (Second-Generation Vehicle-to-Grid Communication Interface)

ISO 15118-20 is the second-generation version of the ISO 15118 vehicle-to-grid communication standard, published in 2022. It adds native bidirectional power transfer (BPT) for vehicle-to-grid, vehicle-to-home, and vehicle-to-building use cases, makes mutual TLS 1.3 authentication mandatory, and supports multi-contract handling for Plug & Charge.

It is not backward-compatible at the application-protocol level with ISO 15118-2. A charger serving vehicles that use either version must therefore implement both protocol stacks and select the appropriate version when the charging session is established.

Key facts

What is ISO 15118-20?

ISO 15118-20 is one part of the ISO 15118 standard for digital communication between an electric vehicle and a charging station.

ISO 15118-2, published in 2014, defined the first-generation network- and application-layer communication used for functions including smart charging and Plug & Charge authentication for one-directional charging. ISO 15118-20, published in 2022, is the second generation of that application layer, and it is a substantial rework rather than a point revision.

Three changes define it. 

First, ISO 15118-20 specifies the messages and communication sequences required for bidirectional power transfer, the messaging that lets a vehicle both draw and return power, enabling standardized vehicle-charger communication for  vehicle-to-grid (V2G), vehicle-to-home, and vehicle-to-building use cases.

Second, it strengthens security. ISO 15118-20 uses TLS 1.3 and mutual authentication, with separate cryptographic profiles and certificate requirements from those used by ISO 15118-2. The vehicle and charging station can therefore verify each other during the secure Plug & Charge handshake. 

Third, ISO 15118-20 introduces new application-layer message sets rather than simply extending those in ISO 15118-2. Supporting both generations therefore, requires separate protocol profiles and careful negotiation of the corresponding TLS versions, cipher suites, and certificates. 

For the general mechanics of ISO 15118, the PKI trust chain, and the full V2G message flow, see the complete ISO 15118 guide for CPOs and eMSPs. This entry stays on what -20 adds and what that means in practice.

Why ISO 15118-20 matters

For charge point operators and eMSPs, ISO 15118-20 sits at the intersection of a regulatory deadline and a potential new energy-services market and revenue stream.

On the regulatory side, Commission Delegated Regulation (EU) 2025/656, which amends AFIR, requires newly installed or renovated publicly accessible AC and DC charging points to comply with EN ISO 15118-20:2022 from 1 January 2027. For private charging points, the requirement applies to Mode 3 and Mode 4 charging. Public charging points offering automatic authentication and authorisation must support both EN ISO 15118-2:2016 and EN ISO 15118-20:2022.

On the revenue side, ISO 15118-20 provides the standardized vehicle–charger communication needed for a parked EV to participate in bidirectional energy services. It standardizes the conversation a vehicle and charger need to negotiate discharge, which underpins energy arbitrage, peak shaving, and grid-balancing services. The catch, covered in Section 6, is that the standard is necessary but not sufficient for that value.

How it works in practice

The most common misread of ISO 15118-20 is treating a “-20-compliant” charger as a “V2G-ready, revenue-generating” charger. They are not the same thing, and the difference decides whether a bidirectional deployment actually earns anything.

ISO 15118-20 governs the communication between the vehicle and the charger. It allows them to agree whether power can flow in both directions, what limits apply, and how charging or discharging should be controlled locally. It says nothing about how the operator’s backend plans, meters, or bills that flow. That job belongs to the backend protocol, OCPP, and specifically to OCPP 2.1, released 23 January 2025, which added the functional block for bidirectional energy management, and a DER Control functional block. It adds native support for ISO 15118-20, a Bidirectional Charging functional block, and a DER Control functional block. It therefore provides a standardized way for a compatible charging station and CSMS to exchange the information needed for bidirectional operation. Complete commercial deployment may also require energy-management, metering, billing, aggregation and grid-integration systems.

The practical consequence: Buying ISO 15118-20-capable hardware without compatible backend and energy-management capabilities limits an operator’s ability to coordinate and commercialize bidirectional energy flows.

On AMPECO’s platform, ISO 15118 is supported natively via Hubject Plug & Charge, and both OCPP 2.0.1 and 2.1, so the vehicle-charger handshake and backend scheduling are handled as a single system.

Interoperability is continuing to mature. CharIN testing programs focus specifically on ISO 15118-20 communication, TLS 1.3, mutual authentication, controlled charging, and bidirectional charging, showing that these capabilities are moving into real implementation and testing while still requiring careful cross-vendor validation. 

7. ISO 15118-2 vs. ISO 15118-20 — What changed?

ISO 15118-20 is a substantial evolution of ISO 15118-2, not a minor revision. The standards use separate application-layer and security profiles, so a charger or vehicle that needs to support both must implement both protocol generations and select the appropriate profile during session establishment.

For CPOs planning infrastructure investments, the practical implication is that the standards will need to coexist. Chargers need ISO 15118-2 to serve vehicles using the first-generation protocol and ISO 15118-20 to support newer functionality and meet the applicable 2027 EU interoperability requirements.

ISO 15118-20 enables bidirectional communication at the vehicle–charger layer, but it does not by itself create a complete V2G deployment. Backend and energy-management capabilities are also needed to coordinate and commercialize bidirectional energy flows.

8. Related terms

• ISO 15118
• Vehicle-to-Grid (V2G)
• Bidirectional charging
• Plug & Charge
• OCPP
• Vehicle-to-Home (V2H)
• Smart charging
• Demand response