Ultimate Guide to EV Roaming: The Executive Playbook

Roaming refers to the ability of an EV driver to access charging infrastructure from various operators without the need for multiple subscriptions or membership cards. With growing pressure from regulators and competition, providing a seamless EV roaming experience is increasingly essential to the survival of Charge Point Operators (CPOs). In this guide, we'll explore the critical aspects of implementing EV roaming. We'll provide clear insights and actionable recommendations to help you make informed and strategic decisions.
Ultimate Guide to EV Roaming: The Executive Playbook

What we will cover:

  • The why's of EV roaming
  • Evaluating Roaming Partners
  • Laying the Foundation of an OCPI Implementation
  • Building and Integrating Roaming Solutions
  • Key Takeaways

The why's of EV roaming

While the cost and complexities of providing roaming capabilities may initially seem daunting, implementing EV roaming offers several compelling benefits that make it a worthwhile endeavor.

Expanded Customer Base and Revenue 

By making your charging stations accessible to a broader customer pool, you can tap into new revenue streams and boost the usage of your existing stations.

Cost Savings

Partnering with other EV charging providers allows you to share the responsibilities and expenses of installation, operation, and maintenance.

Enhanced Customer Experience

Improving services through EV roaming can enhance customer satisfaction and foster brand loyalty.

Competitive Advantage

By offering EV roaming, you differentiate your charging network from competitors and position yourself as a forward-thinking, customer-centric provider.

Regulatory Compliance

As the EV industry matures, governments and regulatory bodies will likely introduce and enforce interoperability standards for charging networks. Implementing EV roaming prepares your charging network for future regulations and may help you stay ahead of the curve and comply with current standards.

Environmental Impact 

Implementing EV roaming encourages more people to use electric vehicles by making charging more convenient. This contributes to reducing carbon emissions and supports the transition to cleaner transportation options.

Evaluating Roaming Partners

Understanding the business advantages of EV roaming, you're now poised to identify the right partners to extend your reach. As a CPO or eMSP, you have two primary options for establishing partnerships:

Bilateral Agreements 

You can forge independent agreements with each partner you wish to collaborate with for roaming. Smaller operators often favor these peer-to-peer arrangements to leverage collective strength in the market.  Other stakeholders, such as car park service providers, may also pursue bilateral agreements with charging operators to provide charging services in their parking areas.

Roaming Hub Integration

By connecting with roaming hubs like Hubject and Gireve, you can grant your customers access to any charging station within the hub's network through a single integration. Some hubs even offer additional services, including real-time monitoring of charging stations, simplified billing, and data analytics.

Though roaming hubs offer multiple benefits, in some markets, CPOs and eMSPs are progressively favoring peer-to-peer agreements for greater flexibility in cost and pricing structures. 

To ascertain the best approach for your business, evaluate your specific use case and thoroughly weigh the pros and cons of each option. Consulting experts in EV roaming implementations can facilitate a more informed decision-making process.

Choosing bilateral partners

If you go the route of bilateral roaming partnerships, evaluating potential partners' capabilities, compatibility, and overall fit with your company's objectives is essential.

Network Coverage: Assess the geographical reach and density of a potential partner's charging network. A partner with extensive network coverage can provide broader roaming access to your customers.

Interoperability Standards: Confirm that potential partners adhere to established interoperability standards such as Open Charge Point Interface (OCPI). Standardized communication ensures seamless data exchange and reduces integration complexity.

Service Quality: Evaluate potential partners' track records regarding service quality, customer support, and network uptime. Reliable partners contribute to a seamless and positive roaming experience for your customers.

Laying the Foundation of an OCPI Implementation

Once you clearly understand your business goals and approach to roaming, it is time to prepare for an OCPI implementation. Below is an outline of the steps we typically follow during the discovery and design phase of an OCPI implementation.

Step 1: Understanding the data model

In the EV world, several industry-specific protocols are used to standardize the terminology, data models, format, and "rules" for when different systems exchange information about their charging points, customers, sessions, transactions, and more.

There are currently four main protocols in use across the global market. Two of these protocols - eMIP and OICP - are proprietary of the large roaming hubs Gireve and Hubject. The other two - OCHP and OCPI - are independent. 

Over the past few years, OCPI has slowly established itself as the "de facto" standard, especially for peer-to-peer roaming. To learn more about OCPI, we recommend you read our guide: OCPI In a Nutshell: A Brief Overview for Modern EV Operators

Determining which protocol will be used for your roaming implementation will help guide you on the next step of the journey.

Step 2: Preparing Your Data

Getting your models and actual data ready for an OCPI roaming implementation can be much more complicated than you think. Before you start, you will likely have to do considerable housekeeping in your current systems. 

Here are some of the considerations you could be facing:

Where Are Your Chargers?

An apparent first focus area is a data entity such as the chargers themselves. Consider questions like:

  • How are you representing your chargers across your systems landscape? What entities and what structure is used?
  • Where do you keep the master data about the chargers and their configuration?
  • How do you uniquely identify them, and their location in the physical world?
  • What connects your charger IDs to your operations or to the operations of others?


As an example of data preparation, in the world of OCPI, using the eMI3-based format as a unique identifier for chargers is recommended. The eMI3 syntax is a unique format that, in simple terms, requires you to present the ID in the format of


e.g., DE*ABC*E123456A, to ensure global identification. So, during your implementation, bear in mind that you might have to rename your chargers or, at the very least, create a mapping between the chargers' internal IDs and the new OC-

PI-compliant ones.

It is common to see setups based on OCPP 1.5 or 1.6, where a complete data restructuring is needed. It might even be necessary to introduce new entities in your data models, new tables into your database, or even completely rethink how you represent your equipment in the field.

Who is Actually Charging?

It is not only physical equipment that needs to be represented according to OCPI standards, but also customers, drivers, and subscribers. In OCPI, a contract ID, per definition, identifies the EV driver within an eMSPs platform, and it is recommended to follow the eMI3 standard here as well. Analogous to the EVSE ID discussion above, the so-called eMA ID syntax should be used instead for driver contracts.

In real-world scenarios, almost no platform represents the hierarchy and details of a customer, billing party, driver, subscription, token, or RFID in quite the same way. Add to this, references and constraints imposed e.g., by a fleet management scenario, and it gets even more complex. Some of the data might even be stored in a master ERP system, meaning that extensive mapping work and data cleanup operations could be needed before getting started with the new models.

Step 3: Aligning the Business Operations

In the above section, we discussed some of the questions and preparations that need to be addressed concerning your current data and models. 

However, the ripple effects of these decisions touch various operational areas:

Technical Operations: Adjusting charging station IDs for roaming may necessitate the distribution of new QR-coded stickers or EVSE IDs, a process that can be both time-intensive and costly.

Customer Support: Involve your support team from the outset. Roaming introduces the possibility of serving customers from other providers.

Financial Management: Determining roaming transaction rates is crucial. It's not just about setting rates but implementing an efficient billing and reconciliation system. Is your finance team prepared for nuanced reporting, possibly spanning multiple jurisdictions?

Pricing Strategy: The OCPI tariff module is comprehensive but may not capture all your pricing intricacies. Whether it's straightforward energy/time-based pricing or layered with additional fees, each model has its challenges.

Step 4: Assess Your IT Landscape and Architecture

For a CPO, there are two typical ways of implementing OCPI. Either it is integrated directly into an existing Charging Station Management System (CSMS), or it is built as a separate platform (or set of services). This separate platform then usually communicates with the CSMS via custom APIs, event buses, and/or other shared resources. 

The approach to pursue depends on factors such as existing architecture, technology stack, and future roadmap activities. Here are some guidelines and pointers to get started:

  • Always start by drawing out your current system or service landscape. Consider what services hold what data, and what are the defined roles of each?
  • Once this is done, the roaming implementation can be fitted. You will also need to inventory all data needed according to the OCPI standard and map this to your own models and data sources.
  • Identify what business logic flows need to be established to and from the OCPI side and what integrations need to be built. Do you, for example, rely on a third-party ERP system that needs extension work?
  • Research what endpoints your CSMS already provides out-of-the-box and whether you would need to extend some of them. Often, some parts of an existing API can be re-used but rarely does it contain everything needed.

Bringing in a Solutions Architect with experience in OCPI can be helpful for all of the above. An experienced professional can guide and support you in completing an analysis, mapping all the integration points, and identifying any dependencies.

Summing up:

  • Make sure you know where your data lives and what structure it has.
  • Consider whether you are ready for data cleaning, or do you need some help?
  • Identify internal stakeholders in your organization, and bring in experts to explain the process to them and support them.
  • Review your current solution architecture and how a roaming service would fit in.

Building and Integrating Roaming Solutions

In the following section, we'll touch on:

  • How to adopt an MVP mindset for roaming
  • Some practical ways you can start small while still thinking big

Most software professionals have witnessed projects that didn't hit the mark, be it due to delays, budget overruns, scope changes, or other hurdles. While there's no magic formula guaranteeing the perfect implementation, especially for projects of vast scale, there are time-tested strategies to minimize risk and sidestep classic mistakes.

Among these strategies, real-world experience, a robust Software Development Lifecycle (SDLC), commitment to agile methodologies, and active project governance stand out as especially effective.

This approach often materializes in the form of an MVP (Minimum Viable Product). Its rise in popularity isn't accidental; countless insightful books and articles have dissected its merits. As we delve deeper, we'll zone in on MVP insights tailored for roaming implementations and OCPI. 

But first, here's a broad framework to guide your MVP thought process:

Identify core functionality

Identify the essential features and functionalities of your implementation that will provide the most value to your users and stakeholders.

Keep it simple

Your MVP should be simple. Avoid overcomplicating it with too many features, and don't worry too much about "future needs". Rather go for robustness.

Test and iterate

Be agile. Test your MVP early and gather feedback. Use this feedback to make necessary changes, and iterate. Fail fast!

Focus on scalability

Ensure your MVP is designed with scalability in mind. Consider how it will handle increased traffic and load. This approach will pay off sooner than you think.

Be cost-effective

As an MVP, it should be cost-effective to develop and maintain. Keep costs low and focus on the business value delivered in each and every iteration.

Have a clear vision

An MVP should be part of a larger vision for your product. Maintain a technical roadmap outlining what future iterations of the product will look like.

MVP Ideas for OCPI & Roaming

Given the critical importance of interoperability on your roadmap today, the first goal should be to implement your roaming project in some capacity. You can always add functionality and expand later on. Minimizing the initial scope is crucial to MVP thinking and speeding up time-to-market. With the right experience, it is possible to identify significant parts of a roaming implementation eligible for an iteration-based separation into the future backlog. 

Here are some practical suggestions for minimizing the initial scope of your OCPI implementation:

Streamline your modules from the get-go.

Consider beginning your CSO journey with a simple integration with a charging station location aggregator. This strategy means you'll only need to set up the locations module to broadcast your station details and their availability. It's a quick win to celebrate!

Focus your role within the OCPI landscape.

Even if you play dual roles in the ecosystem (both CPO and eMSP), start by establishing just one. This strategy effectively slices your initial development workload, setting you up to apply insights from the first phase to the next.

Lean into the "pull" method.

While OCPI doesn't mandate the "push" method, starting with only using "pull" minimizes the initial logic you'll need. When you're ready to expand to both methods, look for opportunities to streamline and repurpose your existing code.

Opt for a minimalist implementation approach.

Be discerning about which data objects or entities you integrate and which query parameters you support. A careful read of the specifications will help you focus on essentials. By leaving out the extras and keeping some processes straightforward, you not only conserve effort but also lay a clearer path for future iterations.

An important benefit of the iterative MVP approach is that you buy yourself some time to think through the bigger picture, prepare your existing platform, align external vendors, and start specifying internal APIs. All while getting started right away writing code, creating some essential scaffolding and groundwork that will be leveraged during the future full-blown implementation.

Some Additional Tips to Ensure Your Success

Have a roaming partner in mind from the start

Before you even start implementing OCPI, have a future roaming partner in mind. The best practice is to survey all your potential partners and research what version of OCPI they support. 

Also, look into things like what methods of push and pull to use in which scenarios and flows. 

Talk through the use cases with your future partners and "negotiate" exactly how things should be set up between you. This can save you time and effort, particularly if you can agree to leave certain optional parts out of the initial implementation.

Understand your counterparts' business and customers

Do they have any rare or special use cases or requirements? On what scale do they operate? How many EVSEs and sessions can you expect to face? Have you taken this volume and performance impact into account? Will their customers call your customer service if something goes wrong at your charging stations, and vice versa?

Know their OCPI platform

Do they use one of the major CSMS systems on the market? Then they will likely need to allocate vendor time or secure support agreements to get technical help if something goes wrong. Have they built their implementation in-house? 

If so, what level of EV knowledge does their development team have, and would it be beneficial to talk developer-to-developer or rather designate a single point of contact with a project manager or business analyst? In either case, check if your contact will be responsive, have a long backlog, work in long sprints, and will be willing to prioritize your project.

Test early and keep testing.

Ensure you have a QA environment ( and preferably one for staging). Use this environment to start testing together with your roaming partner as early in the project as possible. 

Exchange credentials and get the environments talking to each other from day one. Then dedicate QA resources in your team and book regular "live" testing sessions together with their team. Work through test cases systematically and retest for each environment. Remember that production data differs from test data; you never know when the configuration may have changed.

Anticipate failure and issues.

No integration is the same. Just because you successfully got through your first OCPI partner integration, the next one might throw up other unanticipated issues. OCPI is an excellent protocol, but at the end of the day, the implementation itself can lead to issues. 

There are many areas for misinterpretation and more bugs than one might expect, even among the major platforms. Prepare to swallow your pride and implement hotfixes, tweaks, and slight side steps from the standard to get things up and running in the field. 

Follow up and reconcile.

Once you are live with an OCPI integration, make sure to follow up by studying logs, running reports, and pulling data for reconciliation from your partners. This is especially important in the early stages of a new partnership, where things can get out of sync for several reasons, for example, temporary disruptions in network performance, systems availability, simple bugs or unforeseen business logic behavior. Keep an open dialogue with your counterparties; you are roaming partners, after all!

The integration of roaming solutions requires a careful approach and strategic planning. Adopting an MVP mindset, understanding your counterpart, and being open to continuous testing and adjustments can pave the way for a successful project. Remember, collaboration and communication with your roaming partner are vital for successfully integrating roaming solutions.

Key Takeaways from the Guide

1. Introduction to EV Roaming:

Roaming allows EV drivers to access multiple charging operators without needing multiple subscriptions or membership cards.

As the EV industry evolves, providing a seamless EV roaming experience becomes a competitive necessity for Charge Point Operators (CPOs).

2. Benefits of EV Roaming:

Expansion and Revenue: Roaming can tap into new revenue streams by making charging stations accessible to a wider customer base.

Cost Efficiency: Collaborating with other EV charging providers can distribute the responsibilities and costs.

Customer Experience: Roaming enhances user satisfaction and brand loyalty.

Competitive Positioning: Offering EV roaming distinguishes a charging network in the market.

Regulatory Readiness: As regulations around EV evolve, roaming prepares networks for potential standards.

Environmental Contribution: Simplified charging can promote EV adoption, contributing to a cleaner environment.

3. Evaluating Roaming Partners:

Two primary options: Bilateral Agreements and Roaming Hub Integration.

Bilateral Agreements: Individual contracts with partners, suitable for smaller operators and stakeholders like car park service providers.

Roaming Hub Integration: Connecting to hubs like Hubject and Gireve offers access to a broader network with a single integration.

Decision-making should consider specific business use cases and market trends.

4. Partner Selection for Bilateral Agreements:

Network Coverage: Consider the geographical reach and density of the partner's charging network.

Interoperability: Ensure partners follow standards like OCPI for smooth data exchange and reduced complexity.

Service Quality: Assess partners' reliability in terms of service quality, customer support, and network uptime.

5. Laying the Foundation of an OCPI Implementation:

Data Model Understanding: Recognize the protocols used in the EV world. OCPI is becoming a "de facto" standard for peer-to-peer roaming.

Data Preparation: Ensuring data is ready for OCPI implementation can be complex. Consider charger representation, ID structure, and data cleanup.

Business Operations Alignment: Roaming affects various operational areas from technical operations to financial management and pricing strategy.

IT Landscape and Architecture Assessment: Evaluate how OCPI integrates with the current IT system, whether through an existing CSMS or a separate platform. A Solutions Architect with OCPI experience can be invaluable.

6. Comprehensive Approach:

Recognize where data is stored and its structure.

Prepare for potential data cleaning or seek expert help.

Engage internal stakeholders early on and educate them about the process.

Review and understand how roaming services integrate with the current solution architecture.

7. Building and Integrating Roaming Solutions - A Recap

Integration of roaming solutions can be a daunting task. The challenges that come with it can range from technical difficulties to delays and budget constraints. However, adopting a strategic approach and a clear vision can ensure the successful implementation of such projects.

8. MVP Mindset for Roaming:

Start Small, Think Big: This is the essence of the MVP (Minimum Viable Product) approach. By focusing on the core functionality, keeping things simple, and continuously testing and iterating, you can achieve more robust results. Also, ensure scalability and cost-effectiveness while maintaining a broader vision.

9. MVP Ideas Tailored for OCPI & Roaming:

Start Simple: Initially, focus on integrating with a charging station location aggregator. This requires only the setup of the locations module.

Define Your Role: Choose one role in the OCPI ecosystem to begin with, either CPO or eMSP.

Utilize the "pull" method: This method simplifies the initial logic, making the starting phase more manageable.

10. Tips for Success:

Choose a Roaming Partner Early: Understand their platform, version, and business model.

Understand the Counterpart: Know their customers, scale of operation, and any special use cases. Ensure mutual customer service responsibilities.

Know the OCPI Platform of Your Counterpart: Ascertain their platform type, technical support availability, and the knowledge level of their team.

Continuous Testing: Start testing early with your roaming partner in a QA environment. Ensure systematic testing through various stages.

Prepare for Challenges: Every integration is unique. Be prepared for unforeseen issues and be open to making necessary adjustments.

Monitor and Reconcile: After going live, actively monitor logs and data. Regularly reconcile with your partners to ensure consistency.

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