Get our comprehensive PDF packed with knowledge on eRoaming, hubs and protocols!

Being an eMobility leader in various projects across multiple startups, Piotr was responsible for OCPI and OCPP integration as well as EMP and CPO platforms development. With extensive expertise in the open standards field and eMobility tech solutions, he is leading teams of experienced developers and contributing with invaluable knowledge and experience.

Piotr Majcher

Certainly, roaming is something known to everyone at this point. However, what that has to do with eMobility?

Being a broad term for services allowing for connection outside of the usual network, roaming turns out to be an on-point solution for EV charging. With many players in the eMobility game (i.e. Charging Point Operators, eMobility Service Providers), some type of a connector is a must. Here’s exactly where eRoaming comes into play allowing for multi-dimensional connection between operators and EV drivers.

In short, eRoaming can be established via the use of hubs and protocols. A hub here can be an open platform which, after subscribing, can be used by many operators, who operate on common terms. This all happens in such a way that a certain charging pool introduced to a common hub can then be easily used by clients (EV drivers) of different providers. Such a solution allows electric vehicle users to charge their car across cities/countries with limited hussle.

In order to facilitate such a solution, the hubs developed their own open protocols, which are essentially responsible for the connection. They also define the functionalities of each eRoaming platform.

Amongst the existing hubs, we can differentiate three major ones. They all come with their own open standards and unify hundreds of CPOs and EMPs as well as millions of EV drivers.

The three biggest hubs and their protocols are:

(eMobility Inter-Operation Protocol - eMIP)

Apart from the proprietary protocols coming from hubs, it’s worth mentioning that there's also an independent one - 

Open Charge Point Interface Protocol (OCPI)

. It allows for eRoaming between the hubs as well as peer-to-peer connection.

To learn more about eRoaming, hubs & protocols, their importance and functionality as well as the future of eMobility - take a look at our exclusive paper covering all that needs to be covered on the topic!

eRoaming Hubs explained

Download our comprehensive PDF and learn about the pricing structures in e-mobility

Although it would seem rather straightforward, the pricing system within the EV charging environment extends further than just to the payments made by electric vehicles right after they charge their car.

Being such an interconnected network of mutual dependencies between numerous involved parties, e-mobility charging services require various levels of settlements.


It must be noted that it takes a few units to build up and manage a charging network. From 

, which manufacture the hardware side of required components (connectors, chargers, cables, etc), through 

, which are responsible for the backend management, all the way to 

, which determine the final user (here: EV driver) experience, there is a whole network of reliabilities.

Put simply and briefly, CPO’s are to establish billing connections with both EVSE and eMSP’s, in order to put the entire charging formation in place, while ensuring all parties receive transparent information and clear instructions.

To facilitate it, there are multiple types of pricings and contracts, some of which allow for complex, dynamic price models. Such undertaking is required so that eMSP’s can shape their end-users pricing often based on certain conditions, leaving the rates flexible.


Interoperability - the core of proper functioning

It should go without saying, that managing a pool of charging stations - oftentimes distributed across entire countries/regions - is not an easy task to handle and can only be achieved via advanced levels of interoperability and clear, unified procedures.

Open Standards are the chief example of how this can be achieved and maintained. Through the utilization of API’s like OICP the flow of information can be sustained in a transparent manner. This allows for a seamless communication and can facilitate the management of a vast majority of proceedings remotely, which comes in handy while developing a state-wide network, especially when there are numerous parties involved.


Knowing the behind-the-scenes nuances and arrangements, we prepared a comprehensive paper portraying the pricing structure within the e-mobility industry. Those who are willing to learn more about tariffs within charging services, should definitely find it useful.

Download our free paper and broaden your horizons with some great knowledge!

E-mobility tariffs. How is the pricing structured within the industry?

Open standards can be a game changer for both eMSP's and CPO's. Here is why.

The initial stages of technologies lead to various types of solutions addressing the same problem. Each company develops a different approach. At the beginning of the XXth century, when commercial electricity had come to the mainstream, multiple energy producers offered power supply with miscellaneous frequencies and voltages. As time passed, governments began to impose certain standards on suppliers. This standard-setting led to the joint effort to create the first power grid.

From the first power plant to the moment when all energy providers linked to the same network, decades passed. This was only possible because they took a mutual direction.

 - literally and figuratively. With global warming, exhaustion of solid fuel resources, and lifestyle changes, companies face the challenge of how to provide accessible new charging forms of green power.

Now, as the e-mobility era is here, we are on the same page, like we were at the very beginning of the XXth century. We already have plenty of providers: eMobility Service Providers (eMSP) and Charge Point Operators (CPO) - two substantial sides of the e-Mobility world. One of the main challenges ahead of this market is to deliver the best user experience, at possible minimum resources use. As usual, user experience is a matter of well-designed apps, customer support, and simplicity itself. But there is an additional fact. End-users need to be able to charge cars at any charging station without being concerned about accessibility. The issue is - having the contract signed with the Charge Point Operators recharging point service. How to achieve this? Partners must take the same course, and this is where the standards start to play a major role. There are two possibilities: Open Charge Point Interfaces or Open Intercharge Protocols. What are the benefits?

The main goal of the Open Charge Point Interface (OCPI) is to allow electric vehicle drivers to charge their cars at any station. OCPI defines a set of modules that cover most cases the driver may need. There are two technical modules that are used to establish connectivity between two platforms using OCPI: Credentials module and Versions module. Other modules are strongly related to real-life use cases. These would be:

Locations - module responsible for sharing information about the Charge Points, like address, geolocation, real-time data about the current status, electrical parameters.

Sessions & Commands - module allows the end-user to start the charging session and be informed about the current status of the charging session.

OCPI is an open standard, and what may be very important for the adopters - it’s very flexible. For instance, CPOs (Charge Point Operators) may implement only the Locations module (apart from two technical mandatory modules) when only sharing Point Of Interest data. With no necessary exposing the eRoaming functionality. But the ultimate goal for many CPOs is to allow end-users to charge their car. In that case, many more modules need to be implemented (Sessions, Commands, CDRs). Some others are optional, even for the eRoaming (Tokens, Tariffs), and that depends on the agreement between certain allies. It’s in terms of how financial flow and security is modeled.

The biggest advantage of having OCPI implemented is that it’s almost a one-time investment. The initial effort is significant, as it might be challenging to transfer internal models and processes to the OCPI. But once it’s done for a partner, it opens the company for quick and cost-effective integration with a lot of other associates.

A bit different concept is proposed by the Berlin-based innovative company - Hubject. Hubject developed its own API (OICP) covering almost the same cases as OCPI. There is one extra. Hubject also acts as a hub. It connects CPOs and eMSPs. Once a company is connected to the Hubject platform, it becomes open for integration with any other comrade being already assigned. That’s a huge advantage because the integration is done once, with one platform, and of course it becomes profitable when it comes to an alliance with multiple partners.

Yet another advantage of the Open Intercharge Protocol is that it’s quite easy to implement. Like with most protocols, the main challenge is to synchronize our internal models with the standard one. What is comforting with OICP - there is not too much to implement. It depends on the level of integration we want to achieve, but it’s enough to implement about 5 HTTP calls to expose eRoaming through the Hubject platform.

Having in mind multiple historical examples, it may be difficult to be a part of a developed market without following widely adopted standards. Initially, it may need some additional effort. But when the standard is implemented, our platform becomes open for the whole market 

. Without it, we would need to spend weeks or months doing the integration with each partner separately.

OICP and OCPI protocols - open standards for CPOs and eMSPs

Actively supported two commercial open standards facilitating EV roaming.

Interoperability demands a flexible approach and cooperation between market participants. For opening the electric car charging market open standards have been established. Two are an initiative of independent associations (responsible for the development of Open Charge Point Interface and Open Clearing House Protocol). The two other open standards for EV roaming are privately held but similarly open and free to apply. Hub operators GIREVE and Hubject offer innovative customer-friendly service networks for cross-border charging. Both hubs actively support network growth. Becoming a marketplace for charge point operators, e-mobility service providers, car manufacturers, energy suppliers, and public institutions Hubject and GIREVE offer a broad range of profitable solutions and facilitated communication benefits.

Hubject’s network expands beyond Europe. At the moment hub operator connects 767 partners in 52 countries offering over 250 000 charging stations. Hubject is a joint venture of the BMW Group, Bosch, EnBW, Enel X, Mercedes-Benz, innogy, Siemens, and the Volkswagen Group. Initiated in 2012, forms now the largest pool of charging stations. Via intercharge, the dedicated e-mobility platform, provides standardized access to charging infrastructure. Besides, Hubject advises automotive manufacturers, charging providers, and other EV-related businesses launching e-mobility services or implementing Plug&Charge with ISO 15118.

GIREVE has been created as a startup by leading French players in electric mobility: Renault, CNR, la Caisse des Dépôts, EDF et Enedis. At the moment GIREVE operates on 31 European markets and offers 185 charging networks with 109 476 charging stations accessible via EV roaming. Following the open policy in November 2020 hub operator announced becoming a Full Contributor of EV Roaming Foundation (the one responsible for the development of the OCPI open standard). This provides enhanced opportunities for partners. For instance, for an operator being already OCPI compliant, there is no extra cost to connect to GIREVE. Offering two standards for interoperability enables innovation and progress for e-mobility.

OICP was designed in 2012 by Hubject - formed by leading automotive experts in Germany. Besides being the roaming platform, Hubject offers technical connection and contractual arrangements for e-roaming. The general structure of the OICP is divided into two parts - for the eMobility Service Providers and Charge Point Operators, nevertheless, the product offer is constantly being developed. Hubject proclaims the OCIP is “the most widely implemented communication standard between European eMSP and CPO systems”. The most recent version, 2.3, was released in October 2020. The newest update of the protocol follows market requirements - improves the POI quality in an upscaling market, calibration law compatibility, data process performance, and offers higher transparency on the different charging use cases. Additionally, Hubject offers helpful and relevant for CPOs set of remote testing functionalities, for complex examination of various use cases. With the recent protocol update, from July 1st, OCPI 2.1 will be withdrawn.

The protocol is publicly available at no cost and requires no registration. From May 2019, OICP became an open-source protocol, free of charge, distributed on Hubject’s website and on open code distribution systems. The aim is to include more stakeholders in the evolution of OICP. The protocol is published under the Creative Commons Attribution-ShareAlike 4.0 International License. This grants easy distribution and to be shared under the same consent. Additionally, Hubject offers Hubject-compatibility certification.

OICP is formed on SOAP (Simple Object Access Protocol) and uses an object-based approach. It’s a real-time protocol, that also offers asynchronous operations. Although a back-up database is provided, Hubject doesn’t actively support downloads to the charging station. The platform maintains a record of the transaction data.

The OICP protocol documentation establishes market roles as follows:

The EV user/owner wants to charge an EV at a charge point/charge station, and has an agreement with the eMSP.

The eMobility Service Provider wants to enable EV owners the access the charge points. In most cases, the eMSP has a valid contract and transfers information with the Charge Point Operator via Hubject’s platform. Hubject offers connection via eMSP aggregator, which enables communication with the platform. This means several eMSPs can integrate via an eMSP aggregator, hence, the sub-partners do not need to associate with Hubject.

The Charge Point Operator (CPO) manages a charge point. The operator has a signed contract and exchanges information via Hubject’s platform. Like eMSPs, several CPOs can integrate via a CPO aggregator. Appropriately the sub-partners do not need to register with Hubject, because the communication with Hubject is done via the CPO aggregator.

Hubject, being a roaming hub, facilitates communication between eMSPs and CPOs via the EV roaming platform Hubject Brokering System.

OICP supports the following functionalities:

Roaming via hub - The CPO and the eMSP system connect to based on web services Hubject B2B Service Platform. Both parties, the CPO and MSP, have an e-roaming contract through Hubject.

Ad hoc payment - ‘Intercharge direct’ is an ad hoc payment dedicated solution integrated in OICP and Hubject platform. This allows any contractless EV owner to charge up and pay at any charging station.

Authorization - Hubject links the IDs of eMSPs or CPOs and SSL certificate information. Then each does or does not authorize the charge session. Hubject’s database performs as back-up, but not actively support downloads from their database to the charging station.

Reservation - An EV owner can book a charge point e.g. via eMSP app. Hubject checks charge point compatibility with the EV.  If matches send the request to the CPO, which in return responds whether the booking was successful. A reservation can also be withdrawn.

Billing - Charge session data is recorded in Charge detail records (CDRs). Hubject passes on the CDR to the eMSP and stores the CDR in the system.

Charge point information - Uploaded charge point information can be distributed between CPOs and eMSPs via Hubject’s platform. The information areas are charge point ID, CPO, charge point name, charge point location (name, address, geocode, type), time zone, opening times, current availability, accessibility, tariffs, authorization modes, means of payment, charge mode, connector type, maximum power, hub connection, support contact number, reservation possible, real-time status information possible, predictive charge point usage, smart charging services, and the date of the last update. OICP maintains flexible pricing based on charge facility, charge point location, and time-of-use.

Real-time charge point information - This covers dynamic charge point availability status and tariff information.

Session information - Session ID, service specifics, charge point ID, authentication data, start and end time of charging, start and end time of connection, starting and stopping meter value, meter value in between, consumed energy, CPO ID, MSP ID.

Remote start/stop - From within the eMSP application, a charging session can be operated.


eMIP is designed and developed by a French start-up. Created in 2013 by leading French players in electric mobility: Renault, CNR, la Caisse des Dépôts, EDF et Enedis with the main objective to provide “open access to vehicle charging stations”. The core business of GIREVE is to offer a roaming platform for eMSPs and CPOs.

The eMobility Interoperation Protocol enables roaming via clearinghouse data. The protocol provides access to charging point databases, and smart charging features. Although the GIREVE’s main market is France, in 2017 expansion covered the connection of European operators in Austria, Germany, Netherlands, Switzerland, Sweden, UK, Italy, Romania, Norway, Czech Republic, Lettonia, Hungary, Denmark, Belgium, Spain, Slovakia, Irland, and Luxembourg. In 2018 GIREVE’s platform was made compatible with the open protocol OCPI. Currently, the roaming platform operates in 28 countries.

The most recent version, eMIP 1.0.7, was released at the end of July 2019. eMIP is open for free although requires registration. GIREVE also proposes certification services. Moreover, to join GIREVE, the before-mentioned certification is required to connect to the platform. The eMIP protocol is open and, when a partner is approved by GIREVE, allows complete benefits. This includes connecting with a different hub platform or conducting peer-to-peer connections. Note, the protocol documentation explicitly declares GIREVE as the hub platform, the eMIP in practice does not apply to peer-to-peer connections. To ensure a high level of architectural openness and up-to-date offering, GIREVE consults with stakeholders potential future functionalities. GIREVE entirely takes responsibility for the eMIP protocol, in contrast to the previously mentioned approaches (commercial and non-commercial), there is no formal eMIP-member association.

eMIP is based on SOAP (Simple Object Access Protocol). Although eMIP is designed as a real-time protocol, it also supports asynchronous operations. The peculiarity of eMIP’s architecture makes it fairly adaptable and flexible. Any new sorts of data messages, or identification methods, can quickly be added via definition tables.

eMobility Interoperation Protocol documentation defines market roles as follows:

The EV user/owner wants to charge a vehicle at a charge point and an authorization medium.

The eMobility Services Providers warrant EV owners different services amongst which EV charging service, rental, car-sharing, navigation services, etc. The eMSP has a B2C agreement with the EV owner/user and a subscription to GIREVE’s platform.

The Charge Point Operator (CPO) accesses charging infrastructure and other services to EV users/owners and has a subscription to GIREVE’s platform.

The data aggregator applies to a system controlling charging infrastructure data in a given area and which can be inquired via GIREVE’s platform.

GIREVE, as a hub, manages the eMobility Services Platform which offers and ensures technical and functional means to standard services between the eMSPs, CPOs, and data aggregators.

eMobility Interopeational Protocol supports the following functionalities:

Roaming via hub - eMSPs, CPOs, and data aggregators join, based on web services, GIREVE’s roaming platform. The protocol documentation indicates GIREVE as the hub platform.

Authorization - eMIP offers several authorization processes.

Synchronous Authorization - check-in via the charge point (e.g. with an RFID card) or via the eMSP (e.g. an app).

Asynchronous Authorisation: Authentication Data Exchange. The eMSPs upload a list of approved subscribers to GIREVE’s platform. The list can be downloaded by CPOs. When charging at the charge point, e.g. via a RFID card, the CPO verifies the ID with the list provided.

Asynchronous Authentication Data Exchange & Synchronous Authorisation covers an event when CPOs do not download the list but request GIREVE to review the EV user ID. The decision on which authorization process to implement lies at the CPO's discretion.

Reservation - An EV driver can reserve a charge point via the eMSP app. (If the option is implemented and supported)

Billing - CDRs between CPOs and eMSPs are exchanged via GIREVE’s platform. This forms the foundation for invoicing. Via Asynchronous Exchange, the eMSP can download a CDR supplied by the CPO at any time, or via Synchronous Exchange - the eMSP gets quickly a CDR uploaded by the CPO.

Static charge point information - CPOs upload charge point information to GIREVE’s platform. GIREVE verifies the CPOs contract before updating their repository. The aforementioned data can be regained by CPOs, MSPs, and data aggregators. The information hold charge point ID, CPO, charge point manufacturer, charge point name, charge point location (address, geocode, type), time zone, opening times, current availability status, scheduled availability status, accessibility, tariffs, authorization modes, payment methods, charge mode, connector type, maximum power, guaranteed power, voltage, amperage, support contact, remote start/stop possible, reservation possible, and the time of the last update.

Real-time charge point information - GIREVE’s platform receives from CPOs the current availability status of the charge point. The CPOs agreement is verified before updating GIREVE’s repository. This includes scheduled status changes (e.g. for reservation).

Charge point search - The “charge point finder” function eMSPs can retrieve a list of charge points located in a given area and fulfill a set of charging criteria, (e.g. connector type).

Session information - Recorded and sent in the CDR - Charge Detail Record, covers the session ID, CPO ID, eMSP ID, EV user ID, charge point ID, contract ID, start and end time of charging session, metering report.

Real-time session information - With offered message service, CPOs can report events to eMSPs, and eMSPs can request actions while a charging session is in progress.

Remote start/stop - A charging session can be started or terminated by the eMSP.

Platform monitoring - GIREVE’s platform introduces a monitoring ability to check whether eMSPs, CPOs, and data aggregators have a valid connection to the platform. Specially designed “Heartbeat” tests the connection. The system sends “Heartbeat” requests to the associated companies.

EV roaming charging software of the e-mobility community

Privately held protocols offer great support and match users’ expectations. Joining at least one hub will be beneficial since emobility operators and providers can easily improve services and provide a top-notch experience. GIREVE and Hubject on a road to EV roaming extend charging infrastructure with additional user-friendly features. A cross-border network is on hand, and the support of emobility experts and industry leaders ensures the coherence and sustainability of the network. Keep in mind that even though both hubs are developing their individual protocols (OICP and eMIP), they also contribute to OCPI and OCHP growth.

OICP and eMIP refine the EV charging experience

The fact that both hubs were created at the initiative of automotive leaders makes the established EV charging e-roaming solution a guarantee of stability and accelerated growth of the whole network. Besides coverage of crucial functionalities, both protocols offer and develop additional services. The proof is in the numbers. Hubject operates on more than 50 markets on 4 continents and GIREVE offers a pan-European connection in nearly 30 countries. In light of the reality that the e-mobility market is growing rapidly and 2020 was a record year for electric car sales, it is expected that the scope of both hubs will continue to expand.

An extensive scientific analysis of the four most commonly developed protocols in terms of the search for the ideal protocol can be found 

Actively supported two commercial open standards facilitating EV roaming. Discover cross-border e-mobility standards for accessible charging network.

eRoaming Hubs explained

15 MARCH 2022 • 15 MIN READ