Quick Answer: OCPI vs OCPP vs ISO 15118
OCPP, OCPI and ISO 15118 are three important EV charging protocols, but they do not do the same job.
OCPP connects charging stations with a backend charging management system. It helps operators monitor chargers, manage transactions, control charging sessions, update firmware and troubleshoot issues remotely.
OCPI connects charge point operators with e-mobility service providers, roaming platforms and partner networks. It helps exchange location data, tariffs, tokens, session data and charge detail records for roaming and partner access.
ISO 15118 connects the electric vehicle and the charger. It enables advanced vehicle-to-charger communication, including authentication, smart charging support and Plug & Charge.
In simple terms: OCPP is for charger-to-backend communication, OCPI is for operator-to-partner communication, and ISO 15118 is for EV-to-charger communication. They are complementary, not direct replacements for one another.
For CPOs, charger manufacturers and EV charging software buyers, understanding OCPI vs OCPP is not only a technical question. It is a business decision about interoperability, roaming, user experience and long-term network scalability.
Why EV Charging Protocols Matter for Interoperability
EV charging interoperability means different chargers, software platforms, vehicles, apps and payment systems can work together reliably.
Without open and well-supported protocols, a charging network can quickly become difficult to scale. A CPO may be locked into one charger vendor. A charger manufacturer may struggle to integrate with multiple software platforms. An eMSP may not be able to access charging locations or tariff data. Drivers may face failed sessions, unclear pricing or too many apps.
This is why EV charging protocols are central to the growth of public, commercial and fleet charging networks.
For a CPO, protocol support affects:
- Which charger brands can be connected to the backend
- Whether chargers can be monitored and controlled remotely
- Whether drivers can access stations through roaming partners
- Whether tariffs and session data can be exchanged accurately
- Whether the network can support future features such as Plug & Charge
For a charger manufacturer, protocol support affects:
- Which markets the charger can enter
- Which charging management systems it can connect with
- Whether customers see the hardware as future-ready
- How easily the charger can pass integration and certification processes
- Whether the charger can support advanced user experiences
For software buyers, protocol support affects the flexibility of the entire EV charging business. A strong charging management system should not only manage chargers today. It should also support roaming, payment workflows, partner integrations and future protocol requirements as the market evolves.
To understand backend platform capabilities in more detail, read our CPMS Complete Guide.
What Is OCPP?
OCPP stands for Open Charge Point Protocol. It is one of the most widely used EV charging protocols for communication between charging stations and a central backend system.
In a typical charging network, the charger does not operate alone. It needs to send information to the backend and receive instructions from the backend. This is where OCPP plays a key role.
OCPP allows a charger to communicate with a charging management system for tasks such as:
- Starting and stopping charging sessions
- Sending meter values and transaction data
- Reporting charger status
- Managing errors and diagnostics
- Updating firmware
- Supporting remote commands
- Enabling smart charging functions
- Handling authorization with RFID, apps or other methods
For CPOs, OCPP is the foundation of day-to-day charging network operation. If a charger cannot communicate properly with the backend, the operator may lose visibility into availability, revenue, faults and customer experience.
For charger manufacturers, OCPP support is often essential for commercial sales. Many CPOs and software vendors expect chargers to support OCPP because it reduces vendor lock-in and improves interoperability.
However, OCPP is not mainly a roaming protocol. It does not primarily connect a CPO to an eMSP. It focuses on communication between the charging station and the backend charging management system.
For a deeper look at different protocol versions and their business impact, read our OCPP version comparison article.
What Is OCPI?
OCPI stands for Open Charge Point Interface. It is a protocol designed to support communication between charge point operators, e-mobility service providers and roaming platforms.
If OCPP is about managing chargers, OCPI is about making charging networks accessible through partner ecosystems.
For example, a CPO may own and operate charging stations. An eMSP may provide a driver-facing app, RFID card or subscription service. Through OCPI, the eMSP can access the CPO’s charging location data, pricing information, availability, session status and billing-related records.
OCPI can support data exchange for:
- Charging locations
- Connector information
- Real-time availability
- Tariffs
- Tokens
- Sessions
- Charge detail records
- Roaming agreements
- Partner access
This makes OCPI especially important for public charging networks, highway charging operators, regional charging groups, white-label networks and eMSPs that want to offer drivers broader access.
For CPOs, OCPI can help increase charger utilization by making stations visible to more users through partner apps and roaming networks. It can also reduce manual partner integrations by using a standardized interface.
For eMSPs, OCPI helps provide drivers with location discovery, pricing transparency and charging access across multiple CPO networks.
However, OCPI does not control chargers directly. It does not replace the backend charging management system. It works at a different layer of the EV charging ecosystem.
If you are building a branded charging network with partner access, explore our White Label EV Charging Software.
What Is ISO 15118?
ISO 15118 is a communication standard between the electric vehicle and the charging station. It is especially known for enabling Plug & Charge, where the driver can connect the vehicle to a compatible charger and the system can automatically handle authentication and authorization.
Unlike OCPP and OCPI, ISO 15118 is not mainly about backend software integration or roaming between operators. It focuses on the communication between the EV and the EVSE.
ISO 15118 can support use cases such as:
- Vehicle-to-charger communication
- Secure identification
- Plug & Charge
- Smart charging communication
- Energy transfer coordination
- Support for future vehicle-grid interaction scenarios
For drivers, the most visible benefit is convenience. Instead of opening an app, scanning a QR code or tapping an RFID card, a Plug & Charge experience can allow the vehicle and charger to exchange the required information automatically.
For CPOs, ISO 15118 can improve the charging experience and support premium network positioning. For charger manufacturers, ISO 15118 support can make hardware more attractive for markets where Plug & Charge and advanced communication are becoming important requirements.
However, it is important not to oversimplify Plug & Charge. It does not work with software alone. It requires support across the vehicle, charger, certificates, backend systems and payment or contract ecosystem. A CPO planning for Plug & Charge should evaluate hardware capability, software readiness, certificate handling and partner compatibility together.
OCPI vs OCPP vs ISO 15118 Comparison Table
| Protocol | Connects | Main Purpose | Typical Users | Software Impact |
|---|---|---|---|---|
| OCPP | Charger ↔ Backend charging management system | Remote monitoring, charger control, transactions, diagnostics, firmware updates and smart charging | CPOs, charger manufacturers, CPMS vendors, fleet operators | Determines charger compatibility, backend operation, remote control and network management capabilities |
| OCPI | CPO ↔ eMSP, roaming platform or partner network | Roaming, tariffs, location data, tokens, sessions and charge detail records | CPOs, eMSPs, roaming hubs, white-label networks, partner platforms | Enables roaming, public network visibility, partner integrations and tariff/session data exchange |
| ISO 15118 | EV ↔ Charger / EVSE | Vehicle-to-charger communication, authentication, Plug & Charge and smart charging support | Automakers, charger manufacturers, CPOs, backend/payment ecosystem partners | Supports Plug & Charge readiness, advanced user experience and future vehicle-grid communication scenarios |
The key takeaway is simple: these protocols solve different integration problems.
OCPP helps the operator run the charger. OCPI helps external partners access the charging network. ISO 15118 helps the vehicle communicate with the charger.
Which Protocol Matters Most for CPOs?
For most CPOs, OCPP is usually the first protocol to evaluate because it affects core network operation.
If the CPO cannot connect chargers to a backend system, the operator cannot reliably monitor charger status, track sessions, manage users, configure pricing or respond to faults. OCPP support is therefore a basic requirement for many charging projects.
However, OCPP alone is not enough for every business model.
If a CPO wants to join roaming networks, work with eMSPs or make chargers visible in third-party apps, OCPI becomes important. Without OCPI or a similar roaming integration, the operator may need custom integrations for each partner. This can slow expansion and increase software complexity.
If the CPO wants to offer a premium charging experience, support Plug & Charge or prepare for advanced EV-to-charger communication, ISO 15118 becomes more relevant. This is especially important for highway fast charging, OEM partnerships, advanced public charging networks and future-ready charging infrastructure.
So the question is not “Which protocol is the best?” The better question is “Which protocol matters most for this business model?”
A workplace charging operator may prioritize OCPP and payment integration first. A public charging network may need both OCPP and OCPI. A DC fast charging network working with OEMs may need OCPP, OCPI and ISO 15118 readiness.
ISO 15118 vs OCPP: Why They Are Often Confused
Many buyers compare ISO 15118 vs OCPP because both are related to charging communication. But they operate between different parties.
OCPP is used between the charger and the backend charging management system. It helps the operator manage the charger remotely.
ISO 15118 is used between the EV and the charger. It helps the vehicle and charging station communicate about identity, charging requirements and advanced functions such as Plug & Charge.
A simple way to understand the difference is this:
OCPP answers: “How does the charger talk to the backend?”
ISO 15118 answers: “How does the vehicle talk to the charger?”
This difference matters during procurement. A charger may support OCPP but not ISO 15118. Another charger may support ISO 15118 hardware features, but the backend may not be ready for Plug & Charge workflows. A software platform may support OCPP-based charger management but still require additional integration for ISO 15118-related certificate and authorization processes.
For CPOs, the safest approach is to evaluate the full charging ecosystem: vehicle compatibility, charger hardware, backend software, certificate management, payment systems and roaming partners.
How Protocol Support Affects EV Charging Software Selection
Choosing EV charging software is not only about dashboards and pricing pages. It is also about integration depth.
A strong software platform should help CPOs manage chargers, users, payments, tariffs, partners and data across multiple sites. Protocol support directly affects how well the platform can do this.
When evaluating a charging management system, ask these questions:
1. Which OCPP versions are supported?
OCPP support affects charger compatibility. A CPO should check whether the platform supports the charger models already deployed and the charger models planned for future procurement.
It is also important to understand whether the platform supports key functions such as remote start and stop, meter values, firmware updates, diagnostics, smart charging and security-related features.
2. Does the platform support OCPI for roaming?
If the business model includes public charging or partner access, OCPI support can be a major advantage.
CPOs should ask whether the platform can exchange location data, tariffs, sessions, tokens and charge detail records with eMSPs or roaming hubs. They should also check how partner settlement and reporting are handled.
For billing and transaction workflows, see our EV Charging Payment Solution.
3. Is the platform ready for Plug & Charge workflows?
ISO 15118 readiness requires more than a checkbox. CPOs should ask how the software handles authorization, contracts, certificates, payment links and backend coordination.
Even if Plug & Charge is not required immediately, planning for it can reduce future migration costs.
4. Can the platform support multi-vendor hardware?
Many CPOs do not want to rely on one charger brand forever. OCPP-based interoperability can make it easier to operate a mixed hardware network, but real-world integration quality still matters.
Software buyers should ask for tested charger compatibility, not only protocol claims.
5. Can the platform scale across sites and partners?
As a network grows, protocol support must work together with business features such as tariff management, revenue sharing, multi-site settlement, tax reporting, user management and white-label branding.
This is why interoperability should be evaluated together with business operations.
Common Mistakes When Comparing EV Charging Protocols
Mistake 1: Thinking OCPI replaces OCPP
OCPI does not replace OCPP because it connects different ecosystem participants. OCPP connects chargers to a backend. OCPI connects operators and service providers for roaming and data exchange.
A CPO may need both.
Mistake 2: Thinking OCPP is enough for roaming
OCPP can help manage chargers, but roaming usually requires operator-to-partner data exchange. That is where OCPI is commonly used.
If a CPO wants drivers from partner apps to access its network, OCPI support is often more relevant than OCPP alone.
Mistake 3: Thinking ISO 15118 replaces backend software
ISO 15118 helps the EV communicate with the charger, but it does not replace the charging management system. The backend is still needed for operations, pricing, user accounts, reporting, payment workflows and network management.
Mistake 4: Treating protocol support as a yes-or-no feature
A vendor may say it supports a protocol, but the quality of implementation matters.
CPOs should ask which versions are supported, which functions are tested, which charger models are integrated, and whether the platform has experience with real operating environments.
Mistake 5: Ignoring future business needs
A small private charging project may not need OCPI on day one. But if the operator plans to open the network to the public, work with partners or expand across regions, protocol support becomes more important.
Software selection should consider both current operations and future expansion.
FAQ
Does OCPI replace OCPP?
No. OCPI does not replace OCPP.
OCPP is used for communication between charging stations and a backend charging management system. OCPI is used for communication between CPOs, eMSPs and roaming platforms.
They solve different problems. A CPO can use OCPP to operate chargers and OCPI to connect with roaming partners.
Is ISO 15118 required for Plug & Charge?
ISO 15118 is closely associated with Plug & Charge because it enables secure vehicle-to-charger communication for automatic authentication.
However, Plug & Charge requires more than ISO 15118 support in one place. It requires compatible vehicles, compatible chargers, certificate infrastructure, backend coordination and payment or contract handling.
CPOs should evaluate the full ecosystem before promoting Plug & Charge as a customer feature.
Can a CPO use OCPP and OCPI at the same time?
Yes. In many public charging networks, OCPP and OCPI are used together.
OCPP helps the CPO manage chargers through the backend system. OCPI helps the CPO exchange data with eMSPs, roaming platforms or partner networks.
For example, a charging session may be started by a driver using a partner eMSP app. OCPI may help handle roaming authorization and session data exchange, while OCPP helps the backend communicate with the physical charger.
Is ISO 15118 the same as OCPP?
No. ISO 15118 and OCPP are different protocols for different communication paths.
OCPP connects the charger and backend system. ISO 15118 connects the vehicle and charger.
They can work together in a modern charging ecosystem, but one does not directly replace the other.
Which protocol should charger manufacturers support?
Charger manufacturers should usually prioritize OCPP support because it helps their hardware connect with charging management systems used by CPOs.
For DC fast chargers, premium public charging, OEM-related projects and future-ready infrastructure, ISO 15118 support may also be important.
OCPI is typically more relevant to backend platforms, CPO systems, eMSPs and roaming integrations than to the charger hardware itself.
Which protocol matters most for eMSPs?
For eMSPs, OCPI is often the most relevant because it helps them connect with CPO networks, access location and tariff data, authorize users and receive session or billing records.
However, eMSPs still depend on the reliability of the CPO’s OCPP-based charger operations and the broader readiness of the ecosystem for features such as Plug & Charge.
Do all EV charging networks need all three protocols?
Not always.
A private workplace charging site may mainly need OCPP-based charger management. A public charging network may need both OCPP and OCPI. A future-focused fast charging network may also need ISO 15118 readiness.
The right combination depends on the business model, user access method, roaming strategy, charger type and long-term expansion plan.
Conclusion: Choose Interoperable EV Charging Software for Long-Term Growth
OCPI, OCPP and ISO 15118 are not competing answers to the same question. They are different tools for different parts of the EV charging ecosystem.
OCPP connects chargers with the backend charging management system. OCPI connects CPOs with eMSPs and roaming partners. ISO 15118 connects the EV with the charger and supports advanced features such as Plug & Charge.
For CPOs, charger manufacturers and software buyers, the best approach is to evaluate protocols based on real business goals. Do you need multi-vendor charger management? Do you need roaming? Do you need partner access? Do you need Plug & Charge readiness? Do you need scalable billing, tariffs and session data across multiple sites?
The more your charging business grows, the more important interoperability becomes.
Choose an EV charging software platform designed for interoperability and future expansion.
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