If you are building or testing a CSMS (also called a CPMS, depending on your vendor or region), you need an OCPP simulator. The right choice depends on your protocol requirements, team size, and how much infrastructure you want to manage. This article compares the main options available in 2026.

What to look for in an OCPP simulator

Before comparing tools, it helps to agree on criteria. A simulator that works for a solo developer validating BootNotification behaviour is very different from one that needs to run 500 concurrent stations in a CI pipeline. Evaluate on:

Open-source options

OCTT (OCPP Compliance Testing Tool)

OCTT is the official test tool from the Open Charge Alliance. It runs predefined test cases against a target CSMS or charger and reports pass/fail. For protocol compliance it is the authoritative option: if your CSMS passes OCTT, it passes the OCA's own test suite.

Strengths: authoritative compliance coverage, official OCA support, free to use.

Limitations: designed for compliance testing rather than load testing or custom scenario scripting. You run its test cases; you cannot freely script your own transactions. OCPP 2.0.1 test cases are still maturing. No REST API or programmatic control.

Best for: final compliance verification before a CSMS goes to certification, rather than day-to-day development.

SteVe

SteVe is an open-source CSMS built at RWTH Aachen University. It runs a real OCPP 1.6 back-end, and some teams use it as a reference CSMS to test their chargers against. It sits on the other side of the connection from a charging station simulator.

Strengths: battle-tested CSMS reference implementation, good for validating charger-side behaviour.

Limitations: requires self-hosting (Docker or Java), not maintained for OCPP 2.0.1, and cannot create virtual charging stations, since it is a CSMS rather than a station simulator.

Best for: teams who want a self-hosted CSMS reference to test physical chargers against.

EVerest

EVerest is an open-source EV charging software stack developed by the Linux Foundation Energy project. It includes a full OCPP 1.6 and 2.0.1 implementation and can simulate hardware modules. It is primarily designed for firmware developers building charger-side software.

Strengths: deep hardware emulation, active Linux Foundation community, covers the full charging station software stack.

Limitations: substantial setup complexity (C++ build, Docker compose with many services). Designed for firmware engineers rather than CSMS backend developers. Scripting concurrent station scenarios requires significant effort.

Best for: firmware teams building charger-side OCPP stacks who need a realistic hardware emulation environment.

ocpp Python library (mobilityhouse)

The ocpp library by mobilityhouse is a Python library for building OCPP clients and servers. It is a building block rather than a simulator: you write your own simulator using it, which gives you full control but leaves you maintaining the simulation logic.

Strengths: clean API, actively maintained, supports OCPP 1.6, 2.0.1, and 2.1. Good for teams who want a custom simulator matching their use case exactly.

Limitations: not a ready-to-use simulator. You write the behaviour and manage the event loop, reconnect logic, meter values, and transaction state yourself.

Best for: teams with Python expertise who need behaviour the existing simulators do not cover, and are willing to maintain their own simulator codebase.

SaaS option: SimItNow

SimItNow is a managed OCPP simulator available as a cloud service. You create virtual charging stations via a REST API, with no installation or infrastructure to manage. Each station connects to your CSMS WebSocket URL and behaves as a real charger: it sends BootNotification, periodic Heartbeats, MeterValues, and responds to RemoteStart/Stop, ChangeAvailability, SetChargingProfile, and all other OCPP 1.6 commands. OCPP 2.0.1 is also fully supported.

Strengths: no setup, so you sign up, get an API key, and start simulating in minutes. The REST API makes it easy to drive from CI scripts. Supports hundreds of concurrent stations, with full OCPP 1.6 and 2.0.1 coverage, plus built-in network fault injection, error simulation, and smart charging profile testing.

Limitations: as a cloud service, it needs your CSMS to be reachable over the internet, or via a tunnel like ngrok or Cloudflare Tunnel for local dev. Not open-source.

Best for: CSMS backend developers who want to test their system quickly without infrastructure overhead, or teams running OCPP regression tests in CI.

Comparison table

Tool Type OCPP 1.6 OCPP 2.0.1 Concurrent stations REST API Setup effort
OCTT Compliance tester Yes Partial 1 (scripted) No Medium
SteVe Reference CSMS Yes No N/A No Medium
EVerest Firmware stack Yes Yes Limited No High
ocpp library Library (DIY) Yes Yes Custom Custom High
SimItNow Managed SaaS Yes Yes Hundreds Yes None

Which should you use?

For compliance certification: use OCTT. It is the OCA's official tool and the only way to get an authoritative pass/fail verdict against the OCPP specification.

For firmware development: EVerest gives you the hardware emulation layer you need.

For CSMS backend development and CI testing: SimItNow is the fastest path. You can be running transactions against your CSMS in under five minutes.

For fully custom scenarios: if your test requirements are unusual enough that no existing tool covers them, the ocpp Python library gives you the building blocks to write exactly what you need.

Many teams use more than one. A common combination is SimItNow for daily development and CI, with OCTT for pre-certification validation.

Create a free SimItNow account and get your API key instantly, with no credit card required.