OCPI billing is the process for billing and settlement of roaming EV charging sessions exchanged between platforms via OCPI (Open Charge Point Interface). It covers how a session is priced, how the Charge Detail Record (CDR) is generated and shared, and how money is settled between the CPO (who operates the charger) and the eMSP (who bills the end user).
How OCPI billing works (typical flow)
OCPI billing is usually built around these steps:
– The eMSP provides a user token (RFID/app identifier) that is recognized via roaming
– The driver charges on a CPO’s charger
– The CPO records the session (time, kWh, connector, tariffs applied, events)
– After completion, the CPO sends a CDR via OCPI to the eMSP
– The eMSP bills the driver based on the received CDR and its customer pricing rules
– The CPO and eMSP settle the wholesale cost and agreed margin/fees on a billing cycle
Key OCPI elements used for billing
OCPI billing relies on a consistent exchange of:
– Tariffs: pricing definitions (€/kWh, €/minute, flat fees, idle fees, conditions)
– Sessions: near-real-time session tracking (optional but useful for transparency)
– CDRs: finalized charge records used for invoicing and settlement
– Tokens: identity mapping for authorization and customer association
– Locations: EVSE/connector metadata that supports correct tariff selection and taxation logic
What is included in an OCPI CDR
A CDR typically contains the fields needed to bill correctly:
– Start and end timestamps
– Energy delivered (kWh) and charging period details
– Total cost breakdown (components per tariff)
– Currency and VAT/tax indicators (implementation-dependent)
– EVSE/connector identifiers and location references
– Authorization reference (token/contract ID)
– Optional penalties or additional fees (e.g., parking or time-based fees)
Why OCPI billing matters
– Enables multi-network access while keeping billing consistent for drivers
– Increases network utilization for CPOs by attracting roaming users
– Provides a standardized basis for settlement and reconciliation
– Supports pricing transparency in eMSP apps (tariffs shown before charging)
– Reduces integration complexity compared to custom bilateral billing formats
Commercial models are commonly used
OCPI billing can support different commercial arrangements:
– Wholesale tariff + eMSP markup (CPO charges a base price, eMSP adds margin)
– CPO tariff pass-through (eMSP bills the same tariff, margin comes from agreed commission)
– Hybrid (pass-through for energy, markup for service fees)
– Subscription-based overlays where the eMSP offers discounts to its customers
Common challenges and pitfalls
– Tariff mismatches: displayed price differs from applied CDR price due to outdated tariff sync
– Inconsistent VAT/tax handling across countries and B2B/B2C contexts
– Data quality issues: missing kWh, wrong timestamps, incorrect EVSE IDs
– Rounding and currency conversion differences are causing reconciliation gaps
– Dispute handling: failed sessions, partial charges, refunds, chargebacks
– Identity gaps when tokens are reused/shared, impacting multi-user billing accuracy
Best practices for reliable OCPI billing
– Synchronize tariffs frequently and version them properly
– Validate CDR completeness and run automated reconciliation checks
– Monitor roaming KPIs: success rate, CDR acceptance rate, dispute rate
– Define clear exception rules and SLAs between CPO and eMSP
– Maintain audit logs and secure API connections (TLS, allow-listing, key rotation)
Related glossary terms
OCPI
Charge Detail Record (CDR)
Roaming
eMSP
CPO
Interoperability billing
Cross-network billing
Tariffs and pricing models
Multi-network access
Invoice automation