HEMS · Home Energy Management System · nymea.io

Run your own energy. Locally. No mandatory cloud.

Q: Is a subscription required?

Community: self-hostable, no subscription. Auto: installed by ETM-Schurig, no subscription, entirely local. Predict AI: a subscription covers the weather and forecast data service; the core control stays local and functional without it.

ETM PowerSync coordinates solar PV, battery, heat pump and EV charger under a single optimisation logic — one that runs at your site, on your hardware. Designed and installed by an RGE-certified electrical contractor in Alsace, France (RGE is the French state certification for energy-efficiency work), with figures you can argue with.

Request a study → See the features

Data processing

100% local

Monitoring

24/7

Foundation

nymea.io

Integration

REST · MQTT

HEMS features

Your whole energy ecosystem, under control

We show the real state of every feature. What is in production, what is partial, what is on the roadmap. No vague promises.

Solar surplus Partial

The load follows your PV output in real time. Starts on surplus, modulates continuously.

Battery management Partial

Coordination between battery, EV and house. Configurable priorities, charging at output peaks.

EV chargers Partial

Green charging takes priority on PV surplus. Porting of further chargers (Keba and others) in progress.

Heat pump Roadmap

The building's thermal inertia as a virtual battery, driven by energy availability.

Load shedding / management Partial

Power shared between charge points. Protects the service connection against overload.

Open data Supported

Your data stays accessible and exportable. Home-automation integration (Home Assistant and friends) with no proprietary lock-in.

Dynamic tariffs Roadmap

Arbitration on national tariff signals — France: Tempo and off-peak hours. Germany: variable tariffs, EPEX spot, grid-responsive control under §14a EnWG. Built per market, not transposed from one.

CO₂ optimisation Roadmap

Charging during the lowest-carbon hours, from the grid operator's own data — RTE eco2mix in France, SMARD (Bundesnetzagentur) in Germany.

Charge planner Roadmap

Departure time plus target level: the system finds the cheapest or the greenest window.

Supported — running in production Partial — building block exists, being industrialised Roadmap — planned, not yet shipped

Live · real-time supervision

See the system working, in real time.

Control dashboard, energy flows, controller log. The demo is connected to our ETM demonstrator — real hardware, real data.

Open supervision →

powersync@demonstrator

# real-time flows
pv ........... 3.4 kW
house ........ 1.1 kW
surplus ...... 2.3 kW → EV
grid ......... 0.0 kW

optimizer .... active
cloud calls .. 0

Local-first

Your data does not leave your home

Plenty of "smart" solutions ship your load curves to an external cloud to optimise them. At ETM, the optimisation logic runs on your installation. That is an architectural decision, not a marketing line.

▸Local processing by default — the optimisation runs on your hardware, not on a remote server.
▸No forced cloud dependency — the system keeps working offline.
▸Open source foundation — nymea.io + the ETM APT repository. Auditable Open Core architecture.
▸Exportable data — REST / MQTT, home-automation integration with no proprietary lock-in.

powersync@local : ~

# the optimisation runs locally
$ systemctl status powersync-optimizer
  ● active (running) · local socket
  cloud calls ............ 0

$ powersync flow --now
  pv .......... 3.4 kW
  house ....... 1.1 kW
  surplus ..... 2.3 kW → EV
  grid ........ 0.0 kW

Commissioning

From study to production

Technical study

A survey of your installation (PV, battery, heat pump, charger, service connection). Sizing and quantified assumptions you can hold us to.

Installation

Fitted and configured by a qualified electrical contractor. The ETM PowerSync controller is deployed on your hardware.

Operation

The optimisation runs locally. You supervise it from the web interface and the app. Follow-up and support included.

Frequently asked

What people ask us most

What exactly is a HEMS?

A HEMS (Home Energy Management System) coordinates every energy device in an installation — solar array, battery, heat pump, EV charger — under one shared optimisation logic. Without a HEMS, each device does its own job in isolation. With one, they talk to each other: the car charges while the sun shines, the heat pump backs off when the surplus is gone.

Is a subscription required?

Community: self-hostable, no subscription. Auto: installed by ETM-Schurig, no subscription, entirely local. Predict AI: a subscription covers the weather and forecast data service; the core control stays local and functional without it.

Is my inverter or heat pump compatible?

The complete, current compatibility matrix lives at docs.etm-powersync.fr. In short: Eastron SDM72/SDM120 meters are supported; porting of further devices (chargers, inverters) is in progress. Every status is stated honestly.

What does an installation cost?

Cost depends on your existing installation (PV capacity, whether a battery is present, how many devices need controlling) and on the tier you choose. We do not publish a price list without context — an individual study is the only way to give you a figure that holds up. Get in touch.

Does the system work without an internet connection?

Yes. The optimisation runs locally on the controller installed at your site. An internet connection can be used for updates and remote access, but it is not required for normal operation.

What size of installation is this for?

There is no inherent capacity limit. What matters is the number and nature of the devices to coordinate (PV, battery, heat pump, charger) — which is exactly what the technical study is for. Get in touch and we will look at your case.