# FAQ

> Stub — frequently asked questions.

## Does ETM PowerSync send my data to the cloud?

No. Control runs locally, on the box, and keeps working without internet. The only
component that connects to the internet on its own is the OpenMeteo weather plugin: it
sends only the site's coordinates (rounded to about 1 km from plugin version `1.15.2+etm2`; version `etm1` in the testing channel sends them unrounded), its altitude and the
orientation of the panels. Measurements, consumption and the tariff stay with you.
Remote access is disabled by default; it opens only if you enable it yourself in the
app. That is an architectural decision, not an option.

## Is the project open source?

The energy engine (`etm-powersync-energy-plugin-etm`) and the plugins are under
GPL-3.0, including the optimiser client built into the engine — everything linked against
nymea is. The engine works on its own, without an optimiser. The
[protocol between the engine and an optimiser](optimiseur/index.md) is open and
published, with a free reference optimiser and a conformance suite: anyone can write their
own. The **ETM optimiser** and its business logic (tariff arbitration, forecasts learned
from your installation), however, are proprietary: they run in a separate process, reached
through that protocol, at your place — on the box or on a machine in your local network.
That process boundary is the heart of the Open Core model — the engine stays free, the
business logic stays proprietary.

## What is the difference between Community and Pro?

Two editions, not three — the prediction layer has not been sold separately since
2026-10-14; it is part of Pro.

- **Community** — the GPL-3.0 foundation, self-hostable: deterministic rule-based
  control, solar surplus, load shedding, [PV production forecast](fonctionnalites/prevision-pv.md)
  from physical models (beta, displayed, not used to decide), REST/MQTT API. No
  subscription.
- **Pro** — installed by ETM-Schurig: adds tariff arbitration and the prediction layer
  (production and consumption forecasts learned from your installation, heat-pump
  thermal inertia). **No
  subscription either**, and everything stays local.

Tariff arbitration and prediction are on the **roadmap**: the Open Core boundary already
exists, the functions it separates are not all shipped. See
[etm-powersync.fr](https://etm-powersync.fr/en/hems.html).