OCPP 2.1 Is the First to Natively Support ISO 15118-20
The charge point to backend protocol adds native support for the bidirectional-capable revision of ISO 15118, completing the chain needed for V2G in production.
OCPP 2.1 is described as the first version of the Open Charge Point Protocol to natively support ISO 15118-20, the revision that carries bidirectional charging, unlocking the full potential of V2G in deployed systems.
The two protocols cover different links in the same chain and are often confused. ISO 15118 governs the conversation between the vehicle and the charge point — the cable end. OCPP governs the conversation between the charge point and the operator's backend. Bidirectional energy flow requires both to understand it: a charger that can negotiate discharge with a car but cannot report or be instructed about it by its backend is not usable for grid services.
That is why native support matters more than a workaround. Vendors have bridged the gap with proprietary extensions, which works within one supplier's ecosystem and fails at exactly the point V2G becomes valuable — when a grid operator wants to dispatch thousands of chargers from many manufacturers as one resource. Interoperability is not a feature of V2G here; it is the entire premise, since a distributed battery assembled from one vendor's hardware is not distributed enough to matter.
Source: EV Plug Fix