E-ROAMING BASICS 101: What is eRoaming and why it is critical for the growth of E-Mobility Interoperability


Think of a scenario where BP accepts only BP Tankpass; Shell accepts only ShellFuel card; likewise every gas station accepts only their own/preferred payment method. If you want to roam (refuel) between multiple gas stations, you will have to possess cards from every gas stations. Does the fueling of car will be easy & seamless anymore?.

This exactly is the issue many of the electric vehicle drivers are currently going through; they end up having contracts (cards) with multiple eMobility providers. 

Fortunately, the E-Mobility Roaming (eRoaming) solves this bottleneck, by allowing the EV driver to access to all available charging infrastructure with a single subscription (card) or a contract with one eMobility service provider.

This article may give an overview on the evolution of eRoaming, why it is important, how to implement, and how does it work in practice.


Traditionally emobility market players did not have distinct roles. The first pioneer CPOs provided access to their public charge points to EV drivers by issuing RFID charge cards. EV drivers could request the charge cards and use these charging cards to start and stop charging sessions at the charging stations operated by the CPO. The contractual agreement associated with the charge card issued determined the tariffs that would be applied for the charging sessions by the EV driver.

As the number of electric vehicles crossed a threshold there was a market opportunity to provide EV driver services and this led to the creation of eMobility service providers. The early EMSPs provided charge cards and an app to ensure that the EV driver could locate charge points and charge their vehicles.

These EMSPs did not own or operate charge points but had contractual agreements with CPOs wherein the backend systems of the CPOs recognised the charge cards and thereby enabled holders of these charge cards to charge at the charge points operated by the CPOs. This was roaming at its premature stages. The exchange of data on rfid tokens was based on a central database accessible to the CPOs and EMSPs who had the contractual agreement.

Range anxiety was and is still the number one cause of concern to switch to electric cars from the traditional internal combustion engine powers cars. The range of the early EVs was quite low. Moreover using a home charging box it took about 10 to 12 hours to charge the car battery to achieve about 80% of the full promised range. 

Drivers in western Europe on an average drive about 12000 km annually. These factors made the accessibility to public charging infrastructure a key selling point for the early market players. A large accessible public charging network made the charge card proposition more attractive for EV drivers. 

For charging at home one requires a home charging box and most importantly a private parking space. We all know that in most of the cities private parking spaces at home is a luxury. Additionally, the early adopters of electric vehicles were taxi service providers and these EV taxis were always on the road and needed access to public charging stations.

The public charging network is still quite sporadic and charge points are installed and operated by CPOs by winning public tenders. Several CPOs owned and operated a their part of the public charging infrastructure in different cities. 

These CPOs realised that the only way to promote EV adoption and hence growing the market would be to open  up their networks to EV drivers having contracts with other eMobility service providers. Hence roaming was born.


Electric mobility ecosystem has many key stakeholders, and when it comes to eRoaming at least charge point operators (CPOs), eMobility service providers (eMSP), and roaming hubs will be involved. An efficient and user-friendly eRoaming ecosystem requires all of them to communicate to each other, there by a need for common protocols arises.

Below illustrations  shall give a brief overview on how the eRoaming was implemented during the initial stages and how it’s being evolved with common protocols and roaming hubs.

Above picture: eRoaming implementations during initial stages (P.C: MDPI publishing)

 Above picture: eRoaming implementations today with common protocols (P.CMDPI publishing)


For CPOs and EMSPs, roaming in practice depends on contractual readiness, technical product readiness and operational readiness. These three go hand in hand and form the basic pillars of eRoaming.

1. Contractual Readiness

A roaming contract is an agreement between two parties creating mutual obligations enforceable by law. The roaming contract is between a CPO and an EMSP that defines the terms and conditions of access to the CPOs public charging infrastructure to the customers of the EMSP.  

Signing the contract by both parties is the first step towards enabling roaming. The roaming contract generally is structured in the following way.

·         Scope and Objective of the agreement
·         Definitions
·         Rights and obligations of parties involved
·         Roaming services
·         Charge detail records
·         Billing process
·         General intellectual property and data protection
·         Liability and termination
·         Appendices
o   Technical roaming setup
o   Pricing
o   General terms and conditions

2. Technical Readiness

eRoaming entails the bidirectional transfer of data between the CPO and the EMSP. Currently data can be exchanged in the following ways.

·         Direct connection of the backend IT systems of CPO and EMSP conforming to the international standard data transfer protocol also known as OCPI.
·         Exchange of data via a clearing house
·         Exchange of data via a roaming hub

Following the OCPI protocol is the most preferred way as it enables a direct connection between partners. Backend systems of the CPO and EMSP are required to exchange the following data in roaming:

1. Authentication data

The customers of the EMSP can be uniquely identified by the RFID card. The data of the RFID card consisting of RFID number and a visual identifier has to be sent from the EMSP to the CPOs backend.

2. Locations data

The CPO must provide the data of the locations its public charging infrastructure to the EMSP. This enables the EMSP to provide the information on the accessibility and availability of charge points to its end customers.

3. Sessions data

The CPO provides a real time information of the charging session to the EMSP. The customer of the EMSP can know the volume of electricity consumed and the price of the charging session.

4. Tariff data

The CPO provides the data on the tariffs that are applied for charging sessions on the charge points.

5. Charge detail record data

The CPO provides the CDR (Charging Data Records) data to the EMSP. The CDR is a collection of all the sessions completed on the charge points of the CPO by the customers of the EMSP. CDRs contain all the details which the EMSP can use to verify the invoice they receive from the CPO.

Billing and invoicing data can be sent automatically from the backend systems of the CPO to the IT systems of the EMSP. However currently this can be also sent manually involving human interaction.

Read more about the roaming protocols here.

3. Operational Readiness

Operation teams of both the CPO and the EMSP have to be ready and equipped to handle day to day operations and tackle operational issues. This also involves providing customer service to the charge card customer of the EMSP when necessary.  

Operation team of the CPO ensures that the customers of the EMSP can charge at the charge points operated by the CPO. The operations teams main focus is to validate the CDRs that are received and ensure that the invoice corresponds to the sessions detailed in the CDRs. Operational details are clearly defined in the roaming contract.


Range anxiety is the number one cause of concern in transitioning to drive an electric vehicle. This range anxiety can be addressed by providing access to a large public charging infrastructure. This would enable that the confidence to buy and use an electric vehicle will increase. This is quintessential for the growth of eMobility. Roaming plays a very crucial part in the growth of eMobility industry.

Hope this article have provided a brief understanding of eMobility roaming and its importance for the growth of the eMobility industry. Do not hesitate to contact us if you would like to know more about how to set up and enable eRoaming for your business.

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