Tap a charge card at a public charger and it looks easy: card accepted, cable in, charging starts.
Behind that simple moment, though, sits a surprisingly busy chain of systems and companies. The charger has to talk to a backoffice. The card or app has to be recognized. Someone has to authorize the session. Tariffs need to be applied. Session data has to be stored. And somewhere down the line, an invoice, settlement file or reimbursement record needs to be created.
That is why EV charging billing in Europe can feel confusing. The driver sees one charging moment. The industry sees a stack of roles.
What happens when someone scans a charge card?
A public charging session usually follows a flow like this:
- 2.A driver taps an RFID card or starts with an app.
- 4.The charger sends an authorization request upstream.
- 6.A backoffice or billing operator checks whether that token is valid.
- 8.The session starts and usage data is recorded.
- 10.When charging stops, the session becomes a transaction record with timestamps, kWh, connector details and card data.
- 12.That transaction then feeds billing, reimbursement, reporting or roaming settlement.
This is the part many people never see. A charging session is not just "a car got power." It becomes a real data object. That matters, because the final bill depends on that data being passed around correctly.
What a CPO, eMSP and backoffice each actually do
This is where the acronym soup begins.
A CPO, or Charge Point Operator, is the party operating the charging points and their technical setup. On the public side, that may be a brand like Allego or Shell Recharge. But the brand on the charger is not always the whole story. The visible brand, the operating platform and the roaming layer can all be different companies.
An eMSP or MSP is the customer-facing mobility provider. That is the party giving the driver the app, account, RFID card, pricing view or invoice. Think of names like Plugsurfing, DKV Mobility, Shell Recharge or a Virta account. The key point is that an eMSP can give access to chargers it does not own.
A backoffice is the software environment behind the charger network. It tracks charger status, authorizes sessions, stores transactions, manages cards, applies logic and makes exports possible. In plain English: it is the operational brain around the charger.
Depending on the setup, platforms such as Last Mile Solutions, GreenFlux, Virta or Monta may sit closer to that operator, platform or roaming-service layer.
Where OCPP and OCPI fit into the billing chain
Two terms get mixed up all the time: OCPP and OCPI.
They are not the same thing.
OCPP is the communication layer between the charger and a central system or backoffice. It is the protocol, maintained by the Open Charge Alliance, that helps the charger report status, receive commands and push session information upstream.
OCPI, governed by the EVRoaming Foundation, lives higher up the stack. It is used for exchange between charging businesses such as CPOs and eMSPs. That is where roaming-related information gets shared: which charge points are available, whether a token is valid, what a session cost and how records move between parties.
A simple way to remember it:
The charger talks OCPP. The roaming world often talks OCPI.
That difference matters because people often assume "roaming" is just a charger feature. It is not. Roaming is a business and data exchange layer on top of charger communication.
Why public roaming feels simple but isn't
Public roaming feels a bit like mobile roaming. You have one card or app, but you can reach many networks.
Except the billing behind it is messier.
You might charge at an Allego station with a DKV Mobility card. The session might be recognized through a roaming relationship. Data might move directly between companies, or through a hub such as Hubject or Gireve. The charger itself is still talking to its own platform through OCPP. And the final session record still needs to end up in the right place for settlement and invoicing.
That is why no single company "owns" EV charging roaming in Europe. It is a network of operators, mobility providers, protocols, hubs and commercial agreements. Some setups are direct. Some go through hubs. Some mix both.
There is also another layer: not every public session starts with a charge card. Under EU rules such as AFIR for publicly accessible charging, ad-hoc charging and transparent pricing matter too. So the public billing landscape is not only about subscriptions and roaming cards. It also includes one-off payment flows.
Home reimbursement is not the same as public roaming
This is another place where people get tripped up.
Home charging reimbursement is usually simpler. One known charger, one driver, one company-car arrangement, one reimbursement or billing flow. Country-specific rules can still matter, especially around metering and compliance, but the architecture is usually more contained.
Private business-site charging sits somewhere in the middle. A company may want employees and visitors to charge, maybe with RFID cards and tariffs, without turning the site into a full public roaming operation.
Public roaming is more layered. The charger may belong to one party, the card to another, and the settlement route to a third. Add ad-hoc charging on top, and the billing logic gets broader fast.
Home charging reimbursement, private business-site charging and public roaming are related, but they are not the same billing problem.
So while these scenarios are related, they are not the same billing problem wearing different clothes.
Where Plugchoice fits if you want flexibility
This is where the story becomes practical.
A lot of charger owners do not just want charging to work today. They want to avoid getting boxed into one billing setup forever.
That is where Plugchoice fits best: as an open, OCPP-native launchpad and flexibility layer. In practical terms, it works as an OCPP Proxy and management layer that can connect chargers to third-party backoffices and billing providers instead of forcing everything into one fixed route.
That does not mean Plugchoice does every part of billing itself. It is better understood as the layer that helps keep options open: charger communication, platform flexibility, integrations and less vendor lock-in.
For installers, site owners and businesses, that matters more than it sounds. Billing models change. Roaming relationships change. Operator roles change. The boring architectural choice you make early can decide how much freedom you still have later.
The simple version to remember
If the whole ecosystem feels messy, that is because it is.
But the clean mental model is this:
- The driver sees a card, app or payment screen.
- The eMSP or payment flow represents the user.
- Roaming data may move directly or through hubs like Hubject or Gireve.
- The CPO and backoffice handle charger operations, authorization logic and transaction records.
- The charger itself talks upstream through OCPP.
- The final output is not just a charging event, but a billable transaction.
Once you see those layers separately, public EV charging makes a lot more sense.
And once you understand that, the value of an open layer like Plugchoice becomes clearer too: not as "the company that does everything," but as the part that helps you connect the right pieces without getting stuck with the wrong ones.