Which standards make it work?
Before the first evening, the installer checks three things: does the car speak the right protocol, does the wallbox, and does the energy manager?
All three have to fit for energy to flow out.
The questionWhich standards does this bidirectional session rely on?
| Connects | For bidirectional | |
|---|---|---|
| ISO 15118-20published 2022 | car and charger | messages for energy in both directions |
| OCPP 2.1released 2025 | charger and backend | functional block for V2X and DER |
| RED III, Art. 20aEU directive | rules and data | new private points, market access |
| AFIR, Art. 14 and 15EU regulation | national reporting | deployment and potential |
The stack of the CCS route this path follows. Sources: ISO, Open Charge Alliance, RED III and the OCA white paper on AFIR.
Car to charger: ISO 15118-20
ISO 15118-20 defines the communication messages and sequence requirements for bidirectional power transfer between car and charging equipment. It is the part of with bidirectional power transfer built into its services.
It is the route of this path, with a connector, not the only one. CHAdeMO has its own protocol for vehicle to home: the CHAdeMO Association lists certified home equipment that uses it, for example a 5 kW unit with the protocol DC version 2.1.
Charger to backend: OCPP 2.1
2.1 adds the bidirectional energy flows, V2X, as a new functional block, together with a block for distributed energy resources and support for ISO 15118-20. Limited forms of were possible before with customised versions of OCPP 1.6 and 2.0.1.
RED III requires that new and replaced private normal power charge points can support and, in line with , bidirectional functions.
Check your understanding
3 questions. Answer all of them to complete this stop. Each answer explains itself.
Which standard defines the messages for bidirectional power transfer between car and charger?
ISO 15118-20 covers car to charger; OCPP 2.1 covers charger to backend.
Which OCPP version added a functional block for V2X?
OCPP 2.1 added V2X and DER control blocks and support for ISO 15118-20.
What does RED III require of new private normal power charge points?
Article 20a(4) requires that they can support smart recharging and bidirectional functionalities in line with AFIR.
- OCPP Open Charge Point Protocol: the open protocol between a charger and its operator's backend. EV charging fundamentals, stop 03 Glossary
- ISO 15118 International standard for the digital communication between car and charger, the basis of Plug & Charge. EV charging fundamentals, stop 08 Glossary
- AFIR Alternative Fuels Infrastructure Regulation (EU) 2023/1804: EU rules for public charging, from payment to coverage. EV charging fundamentals, stop 08 Glossary
- Combo 2 The DC connector of the combined charging system: the Type 2 shape with two DC pins below, required at public DC points in the EU. Charging hardware, stop 03 Glossary
- Bidirectional charging Smart charging in which the electricity can also flow from the car's battery back to the charging point. Stop 01 Glossary
- V2H Vehicle to home: the car powers the house behind its meter through a bidirectional wallbox. Stop 02 Glossary
- Smart charging Charging whose power is adjusted in real time, based on information received electronically, for example from the grid operator or a price signal; EU law calls it smart recharging. Stop 01 Glossary
- ISO: ISO 15118-20:2022 and Amendment 1:2026 (AC DER service, MCS service, improved security). https://www.iso.org/standard/77845.html. Checked 09 Oct 2026.
- Open Charge Alliance: Open Charge Point Protocol (OCPP): versions 1.6, 2.0.1 and 2.1. https://openchargealliance.org/protocols/open-charge-point-protocol/. Checked 09 Oct 2026.
- EUR-Lex: Directive (EU) 2023/2413 (RED III), Article 20a inserted into Directive (EU) 2018/2001. https://eur-lex.europa.eu/eli/dir/2023/2413/oj. Checked 09 Oct 2026. © European Union, reused under Commission Decision 2011/833/EU.
- Open Charge Alliance: AFIR and OCPP, white paper v1.0, January 2024: bidirectional charging. https://openchargealliance.org/wp-content/uploads/2025/05/ocpp_and_afir-white-paper.pdf. Checked 09 Oct 2026. Licence: CC BY-ND 4.0.
- ISO: ISO 15118-20:2022 and Amendment 1:2026 (AC DER service, MCS service, improved security). https://www.iso.org/standard/77845.html. Checked 09 Oct 2026.
- CHAdeMO Association: Certified products: TSUBAKIMOTO CHAIN eLINK (TPS10), 5 kW, communication protocol V2H protocol DC version 2.1. https://www.chademo.com/wp2016/?p=12048. Checked 13 Oct 2026.
- Open Charge Alliance: Open Charge Point Protocol (OCPP): versions 1.6, 2.0.1 and 2.1. https://openchargealliance.org/protocols/open-charge-point-protocol/. Checked 09 Oct 2026.
- Open Charge Alliance: AFIR and OCPP, white paper v1.0, January 2024: bidirectional charging. https://openchargealliance.org/wp-content/uploads/2025/05/ocpp_and_afir-white-paper.pdf. Checked 09 Oct 2026. Licence: CC BY-ND 4.0.
- EUR-Lex: Directive (EU) 2023/2413 (RED III), Article 20a inserted into Directive (EU) 2018/2001. https://eur-lex.europa.eu/eli/dir/2023/2413/oj. Checked 09 Oct 2026. © European Union, reused under Commission Decision 2011/833/EU.