What is OCPP? How it works and why it has evolved

Contents

What OCPP connects Why a common protocol emerged How charging needs shaped OCPP OCPP 1.6: coordinating charging within shared capacity OCPP 2.0.1: a clearer view inside the station OCPP 2.1: charging as part of an energy system How certification supports interoperability

OCPP (Open Charge Point Protocol) is an open communication protocol between electric vehicle charging stations and a Charging Station Management System (CSMS). Maintained by the Open Charge Alliance (OCA), it defines how they exchange information for authorization, charging sessions, monitoring and remote operation.[1][6]

What OCPP connects

A charging network needs information to move in both directions. Stations report what is happening on site; the management system sends instructions back. OCPP supplies a common set of messages for this exchange, allowing equipment and software from different suppliers to work through an open interface.[6][7]

A vehicle connects to a charging station; the station exchanges OCPP messages with a management system. Vehicle-to-station communication is a separate link. — Figure 1. Vehicle, charging station and management system, from left to right. The blue area identifies the OCPP link. The vehicle-facing link may use specifications such as ISO 15118; its communication endpoints differ from those of OCPP.[1][5]

For a session using central authorization, the station submits a user identifier to the CSMS. It then reports the session and meter readings, providing a record of charging activity. The CSMS can also request remote actions, such as stopping a session, unlocking a connector or updating firmware.[6]

OCPP also carries availability information, faults and diagnostic logs. Together, these functions let an operator observe and manage a network without handling every action at the charger.[6]

OCPP 1.6 offers SOAP and JSON communication variants. In the JSON variant, messages travel over WebSocket; OCPP 2.0.1 also uses JSON over WebSocket. JSON describes the message data, while WebSocket provides the connection used to exchange it.[1][3][7]

Why a common protocol emerged

The original problem was connecting a network built from different suppliers’ chargers. In 2009, ElaadNL, a nonprofit founded by Dutch distribution system operators, wanted to procure equipment from multiple vendors. With no common information-exchange specification available, it began developing OCPP. Version 1.0 followed in 2010, and stewardship passed to OCA in 2014.[2]

An open interface reduces dependence on a supplier’s proprietary communication method. For a network that will grow and change over time, that creates a shared basis for integrating stations and management software.[7]

How charging needs shaped OCPP

Version changes are especially informative when read alongside the problems they address. OCPP 1.6, 2.0.1 and 2.1 illustrate an expanding management scope: coordinating charging demand, understanding equipment in greater detail, and supporting energy flows in both directions. These needs overlap; each stage below highlights a representative change.

OCPP 1.6: coordinating charging within shared capacity

Consider a parking facility where several vehicles charge at once. Starting each session is only part of the task: the stations also share an electrical capacity limit. A management system can account for that limit when setting charging schedules, then send the instructions to the stations through OCPP.[7][8]

Smart charging support arrived with OCPP 1.6 in 2015. Charging profiles provide a way to communicate current or power limits over time, supporting load management and adjustments to when charging takes place.[1][7]

A management system sends charging limits to four stations. Equal green bars depict equal power limits in this illustrative arrangement. — Figure 2. Blue lines carry instructions from the management system to four charging stations. Equal green bars represent equal limits in this example; a charging strategy can assign different limits as capacity and demand change.[3][7]

The distinction is useful: the management strategy decides how to allocate capacity, while OCPP communicates the resulting schedules and limits. In this example, the protocol gives a shared electrical constraint a form that several separate devices can act on. That is a practical step beyond managing each charger in isolation.

OCPP 2.0.1: a clearer view inside the station

More complex chargers brought a need for more detailed configuration and monitoring. Released in 2020, OCPP 2.0.1 introduced a device model that relates settings and observations to individual components. For example, an operator can configure a notification when a power-conversion component’s temperature crosses a threshold.[3]

Transactions also became more expressive. OCPP 2.0.1 allows configurable start and end conditions and brings transaction reporting into a unified TransactionEvent message. Cable connection, authorization and energy delivery need not mark the same moment.[3]

These changes help explain the move towards richer descriptions of both equipment and its use: an operator needs to locate a problem within a station and reconstruct how a charging session unfolded. This was a structural redesign; OCPP 2.0.1 is not backward compatible with 1.6.[3]

OCPP 2.1: charging as part of an energy system

When a vehicle can export power, managing charging also involves the opposite direction of energy flow. OCPP 2.1, released in 2025, adds bidirectional charging, ISO 15118-20 support and distributed energy resource (DER) control. It builds on 2.0.1 while preserving compatibility with its application logic.[1][2]

Seen together, these additions suggest a wider role for charging infrastructure. The vehicle can be considered a controllable energy resource as well as an electrical load, and management must coordinate charging and discharging. The progression is towards a richer relationship between vehicles, charging equipment and the surrounding energy system.

Three rows depict an expanding management scope: coordinating several chargers, monitoring components within a station, and connecting charging infrastructure to bidirectional vehicle and grid energy flows. — Figure 3. Three representative changes, from top to bottom: coordinating charging demand, managing station components, and bidirectional energy interaction. Blue arrows show information exchange. In the bottom row, green arrows depict electrical energy flow; the gray dashed line connects grid-side management with the charging management system.[1][3][8]

How certification supports interoperability

A shared specification defines the exchange; certification checks an implementation against the applicable requirements. OCA’s certification program uses independent testing laboratories to assess OCPP implementations.[2][4]

For OCPP 2.0.1, the Core profile is mandatory for certification. Advanced Security, Smart Charging and ISO 15118 Support are optional certification profiles. A certificate’s version and profile scope therefore describe which capabilities have been assessed.[4]