Interoperability by Design: Why OCPP and OCPI Decide How Fast a Charging Network Can Grow

Key takeaways

• OCPP connects charging stations to the back office (CSMS). OCPI connects a charge point operator to mobility service providers and roaming hubs.
• OCPP 2.0.1 became an international IEC standard in 2024. OCPP 2.1 followed in 2025.
• EU law does not prescribe OCPP or OCPI for public charging today, and roaming is not mandatory.
• France and the Netherlands already ask for open protocols in subsidies and public tenders.
• Since 2025, OCPP certification is linked to a specific firmware version, which makes it easier to check what is installed.

_{Sources: Open Charge Alliance, OCPP Achieves International Standard Status!; European Commission, Questions and answers on the regulation on the deployment of alternative fuels infrastructure; Advenir, Cahier des charges Infrastructure collective; Nationale Agenda Laadinfrastructuur, Wegwijzer Open Markt & Open Protocollen bij contractering; Open Charge Alliance, Renewed OCPP Certification Program launched}

OCPP vs OCPI: What is the Difference?

OCPP and OCPI each cover a different link in a charging network. 

• The Open Charge Point Protocol (OCPP) carries everything between a charging station and the charge point management system: starting and stopping sessions, status messages, meter values, firmware updates and smart charging commands. 

• The Open Charge Point Interface (OCPI) connects that management system to the outside world, so that mobility service providers can show the charge points in their apps, start sessions and receive the charging data they need for billing.

OCPI can be used directly between two parties or through a roaming hub that connects many operators and service providers at once. Both models rely on the same principle: one standard interface instead of a separate integration for every partner.

Read more about the roles of charge point operators and mobility service providers

_{Sources: ElaadNL, Interoperability; Open Charge Alliance, OCPP Achieves International Standard Status!; Open Charge Alliance, OCPP 2.1 edition 1 is now officially published by IEC as IEC 63584-210: 2025; EVRoaming Foundation, OCPI}

Why Does a Closed System Limit Growth?

A charging station that only works with one back office ties the operator to that supplier’s software, pricing and development plans. Switching to another back office then often means reconfiguring or even replacing hardware. 

With OCPP, the charging stations and the back office can be chosen separately, so a network can change software without touching the hardware in the field. The same freedom matters when a supplier changes its pricing or stops supporting a product: stations that speak OCPP can be moved to another back office and keep running.

The same applies to roaming. Without a common interface, every new service provider requires its own integration project. With OCPI, one connection opens the network to many partners. 

The scale of roaming shows why this matters: in February 2026, a single European roaming platform reported more than 687,000 connected charging points in 28 countries, while the EU counts around 1.16 million public charging points in total.

_{Sources: GIREVE, Roaming in Europe – February 2026; European Alternative Fuels Observatory, EAFO Data Update & News Flash September 2026}

What Does European Regulation Require?

European rules push towards open, connected charging, but they do not prescribe OCPP or OCPI for public charging today. The AFIR regulation requires public charging points to be digitally connected, to offer ad hoc payment and, for new points, to support smart charging. Since April 2026, operators must also share static and dynamic data with national access points in the DATEX II format.

The standards regulation that supplements AFIR makes ISO 15118 mandatory for the communication between vehicle and charging point, with ISO 15118-20 required from 1 January 2027. It does not mention OCPP or OCPI. The European Commission also considered making roaming mandatory, but decided against it.

For charging points in buildings, the revised energy performance of buildings directive (EPBD) goes further: they must operate on non-proprietary and non-discriminatory communication protocols and standards. The Open Charge Alliance has asked the Commission to make OCPP 2.1 mandatory in the ongoing AFIR review.

Read more about AFIR and ISO 15118

_{Sources: EUR-Lex, Directive (EU) 2024/1275 on the energy performance of buildings; Open Charge Alliance, OCA Response: Call for Evidence for the Review of EU rules on Alternative Fuels Infrastructure; EUR-Lex, Regulation (EU) 2023/1804 on the deployment of alternative fuels infrastructure; EUR-Lex, Commission Implementing Regulation (EU) 2025/655; EUR-Lex, Commission Delegated Regulation (EU) 2025/656; European Commission, Questions and answers on the regulation on the deployment of alternative fuels infrastructure}

Where do National Rules Already ask for Open Protocols?

Some countries already go further than the EU. In the Netherlands, the national charging infrastructure agenda advises municipalities to encourage OCPP and OCPI in public tenders, and the model tender set for public charging points requires charging data to reach service providers via OCPI. A market study for the Dutch government from September 2026 advises making OCPI mandatory.

In France, the Advenir subsidy programme requires OCPP 1.6 or later for collective charging infrastructure, and an interoperability certificate from a roaming platform for on-street charging points. In Belgium and Germany, public rules and concessions ask for interoperability and open data, without naming a specific protocol.

_{Sources: Nationale Agenda Laadinfrastructuur, Wegwijzer Open Markt & Open Protocollen bij contractering; NKL via TenderNed, Basisset AC, Standaardisatie voor publieke laadpalen; RVO, Eindrapport Onderzoek marktordening publiek toegankelijk laden; Advenir, Cahier des charges Infrastructure collective; Advenir, Cahier des charges Prime voirie; Vlaamse overheid, Besluit van de Vlaamse Regering over de laadinfrastructuur voor elektrische voertuigen; Bundesministerium der Justiz, Ladesäulenverordnung (LSV)}

What Should be Checked Before Choosing Hardware and Software?

Interoperability is easiest to secure at the moment of purchase. A few questions help to assess whether hardware and software leave room to grow:

• Is the charging station certified by the Open Charge Alliance for the exact firmware version that will be installed? Since 2025, the certificate includes a firmware hash.
• Which OCPP version does it support today, and is there an upgrade path to OCPP 2.0.1 or 2.1? Since 2026, OCPP 2.1 implementations can be tested with the Open Charge Alliance’s compliance test tool, which makes it easier to ask suppliers for test results.
• Which OCPI version does the back office support, and which roaming hubs and service providers is it already connected to?
• Can charging data, tariffs and station configurations be exported if the back office changes?

Moving from OCPP 1.6 to version 2.x is usually a migration project rather than a simple update. That is covered in more detail in our article on ISO 15118-20 from 2027.

Read more about what changes with ISO 15118-20

_{Sources: Open Charge Alliance, Renewed OCPP Certification Program launched}

What Does This Mean for a Growing Network?

Open protocols keep the important choices open: which hardware to install, which back office to use and which partners to connect to.

For a charge point operator, that freedom becomes more valuable with every site that is added. As networks expand across borders and more drivers reach them through roaming, interoperability is increasingly decided at the design stage, long before the first session starts.

Frequently Asked Questions

What is the difference between OCPP and OCPI?

OCPP is the protocol between a charging station and its back office. OCPI is the protocol between a charge point operator and mobility service providers or roaming hubs, so that drivers with other apps and charge cards can use the network.

Is roaming mandatory under AFIR?

No. The European Commission considered making roaming mandatory when preparing AFIR, but decided against it. AFIR does require public charging points to offer ad hoc payment, and an app that only works with one operator does not count as ad hoc payment.

Is OCPP mandatory in the EU?

No, EU law does not prescribe OCPP for public charging today. The EPBD requires charging points in buildings to use non-proprietary protocols, and some national subsidy schemes, such as Advenir in France, require OCPP.

Does AFIR require OCPP compliance?

No. AFIR and the standards regulation that supplements it require ISO 15118 for the communication between vehicle and charging point, but they do not require OCPP. AFIR does require public charging points to be digitally connected and new points to support smart charging, which in practice usually runs through a back-office protocol such as OCPP. The Open Charge Alliance has asked for OCPP 2.1 to become mandatory in the ongoing AFIR review.

Which OCPP version should a new charging network use?

OCPP 1.6, usually implemented as OCPP 1.6J (the variant that exchanges messages in JSON), is still widely used. OCPP 2.0.1 and 2.1, however, are now international IEC standards. Version 2.1 adds support for ISO 15118-20, bidirectional charging and ad hoc card payment, which makes it the most future-proof choice for new installations. Manufacturers can now test their OCPP 2.1 implementations with the Open Charge Alliance’s compliance test tool.

What does OCPP certification prove?

Certification by the Open Charge Alliance shows that a product has been tested by an independent lab against the OCPP specification. Since 2025, the certificate is linked to a specific firmware version. The certification programme covers OCPP 1.6 and 2.0.1; for OCPP 2.1, a compliance test tool is available, which manufacturers use to prepare for certification.