OCPP & California Pricing Requirements

The National Conference on Weights and Measures in the USA has issued a document with checklists and test procedures for electric vehicle fueling systems, which has been adopted by the California Division of Measurement Standards (DMS).

Many requirements in the checklists apply to capabilities of the charging station (e.g. having a display or how to display prices), but in some cases it poses requirements for information that is being exchanged between charging station and CSMS (back-office).

This OCPP whitepaper explains how price and cost information can be communicated to the customer with OCPP 1.6 by creating a few custom extensions. It continues to show how this can be achieved in OCPP 2.0.1 with standard messages. A customization of a single message is required if real-time cost calculation on the charger is needed.

Section ‘Checklist Items Requiring Attention’ summarizes the items for which no direct support exists in OCPP and offers alternative solutions. Finally, the ‘Appendix: Relevant Requirements per Section’ lists all requirements from the checklist that are relevant to OCPP.

Based on experiences from first implementations in the field this document has been updated. The running cost information is now sent in a structured JSON-format, which will result in more standardized implementations.

The new format also enables the charging station to calculate and display a running total in between the
periodic cost updates that it receives from the back-end.