When you charge your EV at a public station using your account from a different network, money flows in surprisingly complex ways. The user sees a single charge on their bill; behind the scenes, that revenue gets split among the CPO that owns the charger, the eMSP that holds the user account, often a hub that brokers the relationship, and possibly other parties.
This article walks through how the economics of OCPI roaming actually work — fees, settlements, margin structures — so you can understand who makes money where and why public charging is priced the way it is.
The basic flow
A simplified example. User charges at a public station.
- User charges 30 kWh at a CPO-operated station.
- Charger’s CSMS records the session and sends OCPI CDR to the user’s eMSP.
- CPO sets a wholesale price with the eMSP — say €0.35/kWh.
- eMSP marks up to retail — say €0.45/kWh.
- User is billed 30 × €0.45 = €13.50 by the eMSP.
- eMSP owes CPO 30 × €0.35 = €10.50.
- eMSP keeps €13.50 - €10.50 = €3.00 (gross margin before its own costs).
If a hub mediates the relationship, the hub takes a cut (typically 1-5% of session revenue), reducing both parties’ shares slightly.
flowchart LR
U[User] -->|pays retail| E[eMSP]
E -->|pays wholesale| C[CPO]
E -.->|fee| H[Hub]
C -.->|fee| H
C -->|energy cost| G[Grid utility]
style H fill:#eef,stroke:#88a
style G fill:#efe,stroke:#8a8For a concrete grounding in these roles, see what a CPO and eMSP are and how a roaming hub works.
The price stack
Components contributing to public charging pricing.
CPO costs (per session)
Energy cost. The actual electricity. €0.05-€0.20/kWh wholesale depending on market and tariff.
Demand charges. Per-kW peak fees from the utility. Often 30-60% of operating cost for DC fast charging.
Capital amortization. A $200K-$500K site amortized over its life. Per-session, this can be €0.05-€0.15/kWh.
Real estate. Land lease or owned-property costs.
Maintenance. Regular service, parts, technician visits.
Network connectivity. Cellular or wired connectivity per charger.
Customer service. Even with eMSP-mediated relationships, CPOs handle some direct customer issues.
Operations staff. Monitoring, support, vendor management.
Payment processing. Card processing fees on ad-hoc transactions.
CSMS software. SaaS fees or amortized in-house costs.
Roaming infrastructure. OCPI integration, hub fees, partner management.
Total cost per kWh delivered for a typical public DC fast charger: €0.25-€0.40 in many markets, with significant variation.
CPO wholesale price to eMSP
The CPO needs to cover its costs plus margin. Wholesale to eMSPs is typically 80-95% of retail.
A CPO billing €0.45/kWh retail to ad-hoc users might offer €0.36-€0.42/kWh wholesale to eMSPs. The eMSP’s retail to its users is somewhere between (say €0.40-€0.45).
eMSP costs
The eMSP has its own cost stack.
Customer acquisition. Marketing, app development, signup flows. Often a major cost.
Customer service. Direct user support.
Billing infrastructure. Payment processing, invoicing, fraud handling.
App development and maintenance. Mobile app, route planner, account management.
OCPI integration. Engineering, maintenance, hub fees.
Cross-network coverage. Building relationships with many CPOs (directly or through hubs).
eMSP retail markup
The markup above CPO wholesale covers eMSP costs and margin. Typical: €0.05-€0.15/kWh above wholesale.
This is why a user might pay €0.45/kWh at a CPO whose direct retail (ad-hoc) is €0.42/kWh — the eMSP’s markup covers their service.
Hub fees
If a hub mediates:
- Per-session fees: €0.03-€0.20 per session.
- Per-kWh fees: €0.001-€0.01 per kWh.
- Percentage of session revenue: 1-5%.
A typical hub-mediated session might give the hub €0.05-€0.30 depending on size and pricing structure.
Hubs also provide settlement services in many cases, which has separate fees.
User-facing retail
What the user pays. Combining all the above:
- CPO cost basis: €0.25-€0.40/kWh.
- CPO wholesale margin: €0.05-€0.15/kWh above cost.
- eMSP retail markup: €0.05-€0.15/kWh above wholesale.
- Hub take: €0.005-€0.05/kWh equivalent.
Total user-facing retail: €0.40-€0.65/kWh in many European markets, $0.35-$0.60 in the US.
Settlement mechanics
How money actually flows.
Without a hub (P2P)
CPO and eMSP have a bilateral contract. Periodically (monthly typically):
- CPO sends summary of CDRs delivered to eMSP during the period.
- eMSP verifies CDR data (matches their own records).
- Either party generates an invoice based on the agreed wholesale rate.
- Payment via bank transfer, typically net-30.
Disputes (mismatched CDRs, missed sessions, calculation errors) are handled bilaterally.
Through a hub
The hub typically handles settlement.
- CPO and eMSP both connected to the hub.
- Hub records all sessions flowing through.
- Monthly, hub calculates net amounts owed between each pair.
- Hub invoices and collects from net debtors.
- Hub pays net creditors.
- Hub keeps its fee.
This netting is efficient when there are many parties — instead of N×N bilateral payments, you have N parties paying or receiving from one hub. In practice, large networks like ChargePoint, EVgo, Electrify America, and Flo in North America, alongside operators reachable through European hubs such as Hubject and Gireve, all rely on this kind of aggregated settlement rather than maintaining a full mesh of bilateral contracts. The OCPI CDR module is what carries the underlying session records these settlements are built on.
Multi-currency complications
Cross-border roaming adds currency. A user from a UK eMSP charging at a German CPO involves GBP and EUR.
Patterns:
- Hub absorbs currency conversion. Charges parties in their home currency; hub takes the FX risk.
- Bilateral conversion. Each pair agrees on currency and FX handling.
- OCPI tariff in both currencies. CPO publishes tariff in EUR; eMSP converts to GBP for user display.
In practice, hubs make this easier; pure bilateral cross-border deals are operationally complex.
What makes public charging expensive
Many users complain that public charging costs 2-4x home electricity. The economics explain why.
Capital intensity. A home Level 2 charger costs $1,500 installed; a public DC fast station costs $200K+. The capital must be recovered through per-kWh pricing.
Demand charges. As discussed elsewhere, demand charges can dominate operating cost for DC fast charging.
Multi-party margins. Home electricity has one party (utility); public roaming has CPO + eMSP + sometimes hub, each taking margin.
Service value. You’re not just paying for electricity — you’re paying for the infrastructure, the convenience, the customer service.
Utilization risk. A public charger may be used 15-25% of the time. The cost basis assumes lower utilization than you might think.
For users, this is a real cost premium that’s worth understanding. For operators, it’s a math reality that has to support the business.
What makes roaming margins thin
A few reasons margins in OCPI roaming are thinner than they look.
Competition. Multiple eMSPs compete for users; price pressure squeezes retail margins.
CPO wholesale floor. CPOs need their wholesale price to cover costs; can’t drop too low.
Hub fees. Eat into both sides.
Operational overhead. OCPI integration, support, dispute resolution all cost money.
Currency / cross-border. Adds friction and cost.
The “easy money” interpretation of roaming is wrong. Margins exist but they require operational efficiency to capture.
Margin optimization strategies
For operators looking to improve roaming economics.
For CPOs
Increase utilization. Fixed costs are fixed; higher utilization spreads them across more kWh.
Negotiate utility tariffs. Demand-charge management is the biggest lever.
Mix direct ad-hoc and roaming. Direct ad-hoc may have higher margin per session; roaming brings volume. Balance.
Premium pricing for premium sites. Highway-strategic locations command higher prices than parking-lot retrofits.
For eMSPs
Build broad coverage. Users sign up for coverage; broader is better.
Differentiate on UX. Better app, better customer service, better route planning → higher willingness to pay.
Negotiate wholesale rates. Volume buys discounts. Direct CPO relationships (vs hub-mediated) can have lower wholesale costs.
Adjacent revenue. Premium subscriptions, partnerships, energy products beyond pure roaming.
For hubs
Scale. More volume → more fee revenue, often with declining marginal cost.
Operational efficiency. Settlement, support, partner management automation.
Adjacent services. Analytics, white-labeling, premium offerings beyond pure transactional roaming.
What users should know
Some things users might want to understand about the economics.
Public charging is expensive because it has to be. The infrastructure costs are real. The multi-party model adds layers. Pricing reflects this.
Different eMSPs have different rates. Shop around for membership; multi-eMSP coverage can save money. A driver holding accounts with, say, EVgo and Electrify America in the US or several eMSPs in Europe can pick the cheapest route for a given charger. This flexibility exists precisely because OCPI roaming decouples the account from the charger.
Ad-hoc is usually more expensive than membership. Drive-up pay-with-card pricing is often 20-50% higher than the same charger via an eMSP membership.
Time-of-use exists. Off-peak public charging is often cheaper. Plan when possible.
Roaming is improving. Coverage and reliability have grown dramatically since 2020. By 2027-2028, expect even better.
The honest summary
OCPI roaming is the technical layer that enables multi-network charging. The economics are multi-party, multi-layer, and not particularly fat-margined. CPOs cover real infrastructure costs; eMSPs cover real customer-service costs; hubs cover real coordination costs. Users pay a premium over home charging because the value chain has more participants. Understanding the economics helps in both pricing decisions and partnership negotiations — there’s room for efficient operators to make money, but it’s not a get-rich-quick business.