The relationship between EV chargers and vehicles is shifting from "one-way power supply" to "intelligent energy and data exchange." ISO 15118-20 is the core protocol behind this change—this article breaks down in plain language its impact on V2G, Plug & Charge, security, and the EU 2027 requirements.
EV charging is evolving from simple power transfer to intelligent energy and data exchange. ISO 15118-2 introduced Plug & Charge, enabling vehicles and charging stations to automatically authenticate, communicate, and start charging sessions with minimal manual intervention; ISO 15118-20 pushes the communication architecture even further.
ISO 15118-20, published in 2022, is the second-generation network and application layer standard in the ISO 15118 series, defining communication between the EV Communication Controller (EVCC) and the Supply Equipment Communication Controller (SECC), including bidirectional power transfer. In 2026, the standard was further supplemented by ISO 15118-20:2022/AMD 1:2026 with AC distributed energy resources, megawatt charging system services, and improved security concepts.
For EV charger manufacturers, charge point operators, and system integrators, ISO 15118-20 is not just a protocol update—it affects communication architecture, cybersecurity, interoperability testing, and future V2G capabilities.
What is ISO 15118-20?
Its formal title is "Road vehicles — Vehicle to grid communication interface — Part 20: 2nd generation network layer and application layer requirements," used to standardize high-level communication between EVs and supply equipment. In practice, it enables vehicles and chargers to exchange the following information:
Charging and discharging capabilities;
Requested and available power;
Billing plans;
Authentication and authorization;
Battery and energy-related parameters;
Charging service negotiation;
Security certificates and encrypted communication.
In one sentence
ISO 15118-20 is the second-generation vehicle-to-charger communication standard, introducing standardized communication for bidirectional power transfer while enhancing security and expanding the communication architecture for future charging applications.
But note: ISO 15118-20 itself does not turn an ordinary charger into a bidirectional charger—it only provides the communication framework for vehicles and supply equipment (EVSE) to coordinate bidirectional services. The charger, power electronics, vehicle hardware, battery management system, grid connection, and local regulations must all support bidirectional operation as well.
ISO 15118-20 vs. ISO 15118-2: What has changed?
ISO 15118-20 is not just a revision of ISO 15118-2—it is a new-generation communication architecture.
Feature | ISO 15118-2 | ISO 15118-20 |
|---|---|---|
Protocol generation | First-generation network/application protocol | Second-generation network/application protocol |
Bidirectional power transfer | Not standardized as a complete BPT service | Defines BPT communication messages and sequences |
Plug & Charge | Supported | Supported, with updated communication and security architecture |
Transport security | Based on TLS 1.2 | TLS 1.3 as a mandatory requirement |
Certificate requirements | Early certificate and key architecture | Updated cryptographic and certificate requirements |
Wireless communication | Limited scope | Expanded communication requirements for conductive and wireless charging |
Automatic connection device | Limited | Explicit communication requirements |
Future high-power services | Early architecture | Framework continues to evolve, incorporating MCS-related services |
The most significant change is bidirectional charging, but the deeper shift is this: chargers and vehicles can exchange more detailed information and coordinate increasingly complex energy services.
1. Bidirectional power transfer: From charging to energy interaction
The most important new capability in ISO 15118-20 is bidirectional power transfer (BPT). Traditional charging is one-way: power grid → EV; bidirectional charging can transfer energy in either direction: power grid ⇄ EV. This enables vehicles and charging platforms to dynamically negotiate charging and discharging parameters, laying the foundation for a variety of energy applications.
Vehicle-to-grid (V2G)
Through V2G, EVs can export stored energy via compatible charging infrastructure and participate in grid-related services. Potential applications include:
Peak load shaving;
Demand response;
Renewable energy balancing;
Frequency and grid support services;
Energy price optimization.
Large numbers of connected EVs can become distributed energy storage, but commercial deployment depends heavily on grid rules, electricity markets, and aggregation platforms.
Vehicle-to-home (V2H)
V2H allows a compatible EV battery to power a home. For example, the vehicle can charge when electricity prices are low or solar generation is high, then power the home when prices are high; depending on system design and local regulations, it may also provide limited backup power during outages.
Vehicle-to-building (V2B)
The same concept applies to commercial properties. Fleet vehicles at offices, warehouses, or industrial facilities can become part of building energy management, coordinating building loads, solar generation, stationary storage, and demand response.
What about V2L?
Vehicle-to-load (V2L) is also widely discussed in the bidirectional energy ecosystem, but it should not automatically be equated with ISO 15118-20-based V2G communication—many V2L implementations supply power directly from the vehicle to external loads and may use different architectures. This distinction is important when selecting charging equipment.
2. ISO 15118-20 does not equal bidirectional hardware
The most common misconception is that protocol compatibility alone enables a V2G charger. That is not the case—a practical bidirectional charging system requires coordination across multiple layers:
Communication layer
The EVCC and SECC must be able to negotiate ISO 15118 communication sequences and correctly exchange charging and discharging parameters.
Power conversion layer
The charger must use power electronics capable of transferring energy in both directions. A one-way DC charger that was never designed for reverse power flow cannot become a V2G charger through a software update alone.
Vehicle layer
The EV itself must support bidirectional energy transfer, including appropriate battery management and vehicle control functions.
Grid layer and site layer
Installation may also require: grid protection, bidirectional metering, energy management, local utility approval, grid code compliance, and backend control.
For manufacturers, ISO 15118-20 compliance should be treated as a complete system architecture, not an isolated software feature.
3. Security: Why TLS 1.3 Matters So Much
Charging communication goes far beyond requesting current and voltage. The modern charging ecosystem involves vehicle identification, user contracts, payment authorization, charging configuration, certificates, and grid directives, so security is the foundation of interoperability. ISO 15118-20 requires TLS 1.3 for secure vehicle-to-charger communication and introduces stricter certificate and cryptographic requirements (larger keys and certificate structures).
For charger developers, the engineering question is not just whether the controller can "speak ISO 15118"; production implementation must also consider:
Certificate storage;
PKI integration;
Certificate verification;
Certificate lifecycle management;
Processor and memory resources;
Secure software updates;
Backend integration.
4. Plug & Charge Continues to Evolve
Plug & Charge is one of the most well-known features of ISO 15118: no scanning QR codes, opening apps, or tapping RFID cards—compatible vehicles and chargers automatically exchange credentials. Simplified flow: connect vehicle → establish communication → authenticate → authorize charging → start session.
ISO 15118-2 already supports Plug & Charge, and ISO 15118-20 builds the second-generation communication and security architecture on top of it. But commercial deployment also involves the entire ecosystem: vehicle certificates, charging station certificates, contract certificates, certificate provisioning, e-mobility service providers, charge point operators, PKI infrastructure, roaming, and backend platforms. Therefore, manufacturers need to plan simultaneously at both the embedded controller level and the backend ecosystem level.
5. Wireless Charging and Automated Connection
ISO 15118-20 also covers scenarios beyond wired charging, including conductive and wireless charging, as well as automated connection devices. With the growth of automated fleet depots, autonomous vehicles, robotic charging systems, wireless charging, and unattended charging operations, reliable machine-to-machine communication is becoming increasingly important—because drivers may no longer actively participate in initiating and supervising charging.
6. Megawatt Charging and the 2026 Amendment
Heavy-duty electric vehicles demand far higher charging power than passenger cars, which has accelerated the Megawatt Charging System (MCS). Rather than describing MCS as a built-in feature of the original 2022 standard, it is better to view ISO 15118-20 as a continuously evolving communication framework. As of 2026, ISO 15118-20:2022/AMD 1:2026 adds AC DER services, MCS services, and improved security concepts. For manufacturers targeting high-power applications such as electric trucks and buses, the communication protocol must evolve in step with connector technology, power conversion systems, and thermal management.
7. What Does the EU 2027 Requirement Mean?
Under European Commission Delegated Regulation 2025/656, from January 1, 2027, newly installed or renovated relevant charging points must meet updated interoperability requirements: public AC and DC charging points must comply at least with EN ISO 15118-20:2022 for interoperability; public charging points offering automatic authentication (such as Plug & Charge) must also comply with both EN ISO 15118-2:2016 and EN ISO 15118-20:2022; newly installed or renovated private Mode 3 / Mode 4 charging points also require EN ISO 15118-20:2022.
Does this mean all European chargers must support V2G from 2027?
No. Compliance with EN ISO 15118-20 does not mean every optional feature (such as bidirectional charging) must be commercially enabled on every charger—mandatory, conditional, and optional features still need to be interpreted according to specific billing use cases. But for EVSE manufacturers, the regulatory direction is clear: ISO 15118-20 must enter European product architecture and roadmaps.
8. Why ISO 15118-20 Is Critical for EV Charger Manufacturers
SECC Architecture
The Supply Equipment Communication Controller (SECC) is a key component for high-level communication between the EVSE and the vehicle, requiring reliable coordination of protocol states, vehicle information, and charging parameters.
Backward Compatibility
The market will not migrate from ISO 15118-2 to ISO 15118-20 overnight. Charging infrastructure must be compatible with vehicles from different generations, manufacturers, and markets. Multi-protocol compatibility and transition strategies become important engineering considerations.
Cybersecurity
TLS 1.3, certificate handling, and PKI integration place additional demands on software architecture and embedded computing resources.
Bidirectional Hardware Design
Manufacturers planning V2G must coordinate: bidirectional power modules, charger control logic, energy meters, protection circuits, and site energy management.
Interoperability Testing
Supporting a standard on paper and communicating reliably with real vehicles are two different things. Different EV platforms behave differently during connection, authentication, parameter negotiation, and charging. Real-vehicle interoperability testing remains a critical part of EVSE development.
9. Why SECC Interoperability Is Increasingly Important
In the ISO 15118 architecture, the SECC sits between the vehicle communication layer and the charging control system. A robust implementation must not only establish the connection but also correctly exchange and coordinate information throughout the entire charging process, including connection establishment, protocol negotiation, parameter exchange, charging control, error handling, and session termination.
Willdigits has conducted real SECC communication compatibility tests on multiple electric vehicles, capturing and analyzing communication messages to verify protocol-level interactions, rather than just checking whether the vehicle can start charging. As protocols and vehicle platforms become more complex, this type of testing is increasingly valuable.
10. What should EVSE manufacturers prepare for ISO 15118-20?
Companies developing next-generation charging equipment should evaluate at least six areas:
Communication controller capability: confirm whether the SECC and main charging controller architecture support the required protocol stack;
ISO 15118-2 and 15118-20 coexistence: plan for the transition period and support vehicles from different generations of standards;
TLS 1.3 and certificate management: evaluate processing resources, secure storage, PKI integration, and certificate lifecycle;
Bidirectional power architecture: if V2G/V2H is required, confirm whether the power stage, metering, protection, and control support reverse power flow;
Backend integration: treat OCPP, operator platforms, Plug & Charge infrastructure, and energy management interfaces as a whole;
Vehicle interoperability testing: verify integration with real vehicles and different EV communication implementations, rather than relying solely on protocol-level simulation.
Frequently Asked Questions
What is ISO 15118-20?
It is the second-generation network and application layer standard for communication between electric vehicles and charging equipment, defining service communication including bidirectional power transfer, and introducing updated security and charging communication capabilities.
What are the main differences between ISO 15118-2 and ISO 15118-20?
ISO 15118-2 established smart charging and Plug & Charge capabilities; ISO 15118-20 introduces a second-generation architecture, including standardized communication messages for bidirectional power transfer and TLS 1.3-based security.
Can ISO 15118-20 enable V2G?
It provides the communication framework required for bidirectional power transfer, but actual V2G operation also requires compatible vehicle hardware, bidirectional chargers, power grid integration, and appropriate regulatory support.
Will an ISO 15118-20 charger automatically support bidirectional charging?
No. Communication protocol support and bidirectional power hardware are independent requirements; both the charger and the vehicle must be designed for reverse energy transfer.
Can ISO 15118-20 replace ISO 15118-2?
It is the second-generation standard, but ISO 15118-2 remains important during the market transition period because many existing electric vehicles rely on the earlier protocol.
Is ISO 15118-20 mandatory in Europe from 2027?
EU regulations require relevant newly installed or renovated public charging points, as well as certain private Mode 3/4 charging points, to comply with EN ISO 15118-20 requirements from January 1, 2027; however, this does not mean every charger must enable all optional features.
What is the role of the SECC?
The SECC (Supply Equipment Communication Controller) is responsible for managing high-level communication on the charging station side and exchanging information with the vehicle's EVCC. It is a key component of CCS- and ISO 15118-based charging systems.
Conclusion
ISO 15118-20 marks a significant shift in EV charging: charging stations are evolving from simple power supply equipment into intelligent energy interfaces that coordinate vehicles, operators, buildings, and even the power grid. Bidirectional power transfer may be the most notable change, but TLS 1.3 security, more advanced certificate management, automated charging, evolving MCS support, and new European interoperability requirements are all reshaping how charging equipment is designed.
For manufacturers, the key question is no longer "Can the charger communicate with the vehicle?" but rather "Can the complete charging system communicate securely, maintain cross-generation vehicle interoperability, and support future energy services?"
Willdigits develops DC charging solutions and charging control components (including SECC, CCU, PCU). If you are evaluating CCS/NACS communication, V2G applications, controller integration, or custom charging solutions, contact us to discuss your project requirements.
