How do you register a home battery in Belgium?

A home battery in Belgium is registered after two checks. Its inverter must be on the Synergrid C10/26 list, and a recognised body must pass the installation under the AREI. Then you notify your grid operator: Fluvius in Flanders, ORES in most of Wallonia, Sibelga in Brussels. In Flanders the notification goes through Mijn Fluvius, with the inspection report and a single-line diagram attached.

You may have called Fluvius and heard that nothing needs to be done. A year later, a letter says you probably have an unregistered battery. The online form then asks for an inspection report you never ordered. Another owner is told on the phone that 10 kVA is the limit, while a forum says 25 kVA.

The cost of getting it wrong is rarely the paperwork. It is an inverter that is not on the list and cannot be registered. Or a failed inspection because a breaker or a drawing is missing. Or a back-up switch that nobody approved. On a large system, each of those means a second visit and weeks of waiting.

Our large home systems go through the same steps as a small battery. In Wetteren, the whole three-phase house runs through the battery: 9 kVA and 15.4 kWh, and everything keeps working when the street goes dark. In Kortenberg, three-phase batteries with 30.8 kWh give full back-up in off-grid mode.

Must you register a home battery, and with which grid operator?

Yes, in all three regions. Since 1 January 2017, every grid user in Flanders must report a storage system to the grid operator. ORES calls the declaration of your own production a legal obligation, and Sibelga has its own battery declaration.

The grid operator needs to know where batteries sit, because they can take and push large amounts of power at the same moment. Fluvius names high peaks on the low-voltage grid, tripping inverters in the street and unsafe situations for its technicians.

The deadline in Flanders is short. The Flemish government site states 30 days after the inspection, while a Fluvius news page mentions three months. Register as soon as you have the report, and you are inside both.

Why do owners get contradictory answers about registration?

Because four sets of rules meet in one small box. Synergrid sets the technical rules for anything that can feed the grid. The AREI is the federal safety code. Fluvius, ORES or Sibelga run the registration. The Flemish regulator writes the plug-in rules.

A phone agent who knows solar panels may not know how a battery inverter is counted. An inspector may read the DIY question differently from a colleague. So people end up quoting whichever answer suited them.

What is the Synergrid C10/26 list, and why must your inverter be on it?

It is the list of production units that Synergrid has checked against its connection rules, C10/11. Every unit that can run in parallel with the Belgian distribution grid needs this type approval before the connection procedure may start.

The list covers inverters for solar panels and batteries, generators, two-way chargers for electric cars, CHP units and wind turbines. For each unit, it links the conformity declaration that the grid operator asks for.

An inverter can be missing for four reasons, Synergrid explains. You looked at an old download, or the approval is still in progress. The model may not be known in Belgium yet. Or it is an old inverter that no longer meets the rules, and may no longer be installed new.

How do you read the C10/26 list for a large home battery?

Look further than the brand name. One row is one exact model, with its firmware and the parts it was tested with. A large or three-phase system raises more questions than a small one.

Three single-phase inverters, one per phase, can form a three-phase system. C10/11 then asks that the design keeps the imbalance between the phases under 5 kVA. For a whole-house battery on 3x400 V, read our article on the three-phase home battery for full back-up.

How much battery power can a home register without a grid study?

With Fluvius, up to 25 kVA of inverter power goes through Mijn Fluvius. On a single-phase connection the ceiling is 5 kVA; on a three-phase connection 25 kVA, with at most 5 kVA of imbalance per phase.

That is where the 10 kVA on the forums comes from. The C10/11 prescription defines a "small installation" with two separate ceilings: one for solar and other production, one for storage. Each is 5 kVA on one phase and 10 kVA on three phases. C10/11 adds that some grid operators allow more and publish their own limit.

Above 25 kVA, Fluvius handles the battery through a grid study. Our article on the Fluvius grid study explains what that involves. In Wallonia, ORES studies installations above 10 kVA in more depth.

What does the inspector check on a home battery?

The inspector checks the change to your electrical installation: the battery circuit, its protection, the earthing and the drawings. A recognised inspection body (erkend organisme) does it on site, before you use the battery.

The AREI chapter on industrial batteries, with its battery rooms and cabinets, does not apply to batteries in household installations. So a home battery is inspected under the general rules of the code. The inspection report then goes with your registration.

Have the single-line diagram ready, with the battery, the inverter and any back-up board drawn in. Fluvius asks for a clear single-line diagram of the battery with the registration. Many owners only find out when the online form blocks.

A home installation is inspected again every 25 years. Fluvius adds that a new check can be wise even when it is not required, for your insurance policy and for fire safety.

What changes when the home battery also gives back-up?

A back-up battery disconnects the house from the grid during a power cut and feeds it on its own. That island mode is exactly what the inspector and the grid rules look at most closely.

For a small installation, C10/11 requires an automatic separation system on every production unit, built into the inverter or placed separately. It stops your battery from feeding a street that technicians think is dead.

Earthing changes too. C10/11 allows a local earth connection only while the house runs as an island. It must be broken before the system runs in parallel with the grid again. In a Victron MultiPlus-II, a ground relay handles that switch.

The Victron Quattro inverters we use in larger systems are Synergrid-approved for use in a parallel system, one that stays connected to the grid. How the back-up itself is chosen is covered in our article on a home battery with back-up power.

When do you need a new inspection or a new notification?

Every change to the battery is reported to the grid operator, but not every change needs a new inspection. Fluvius lists the cases.

Adding a battery to existing solar panels often means a new hybrid inverter. That is a change to the solar installation as well. Our article on adding a battery to an existing SMA or SolarEdge installation covers the technical side.

How does registration go, step by step?

Registration is the last step, not the first. The order below keeps you from redoing work.

Registration takes time. In September 2026 it reported a backlog and was handling notifications from late December 2025. When you register solar panels and a battery together, the confirmations can arrive separately.

Late registration has a price. Fluvius warns of an administrative cost when the notification is left undone. In Wallonia, ORES says that access to the grid can be refused when a production installation is not declared in time.

What should Walloon and Brussels owners check before they add a battery?

In Wallonia, the declaration goes to ORES together with a smart meter. ORES calls that meter mandatory and free for new production, and advises asking for it a few weeks before the work ends.

Are you still on the compensation scheme, the meter that runs backwards? ORES warns that the compensation ends when the installation grows by more than 1 kWe or passes 10 kVA. Ask ORES how your battery is counted before you sign.

In Brussels, Sibelga runs its own battery declaration. Building a house in Wallonia that must run largely on its own power? Our article on an energy-autonomous house in Wallonia looks at what to ask your builder and installer.

What happens when you ask us about a home battery?

We start from what must keep running in your house, and design the system so it can be registered.

1. Step 1: You send us the facts. Your consumption, your connection (single or three-phase) and the loads that must keep running.
2. Step 2: We measure and calculate. Our engineering office sizes the batteries, inverters and back-up for your home.
3. Step 3: Installation, with the drawings the inspector and the grid operator ask for.
4. Step 4: You follow it in real time. You see production, storage and consumption in the app.
5. Step 5: The system grows with you. It can be extended with extra panels or storage.

Our home batteries range from a few circuits on back-up to a full no-break house on three phases.