Solar panels for your business: everything you need to know about the Fluvius 25 kVA threshold

Are you considering solar panels for your business premises? The administrative process has become significantly more straightforward in recent years. Since early 2024, Fluvius has raised the threshold between small and large production installations from 10 kVA to 25 kVA — a change with concrete implications for your installation procedure, timeline and options.

Last updated: June 2025 - This article covers the rules applicable in Flanders (grid operator Fluvius). Rules in Wallonia and Brussels differ.

What is the Fluvius 25 kVA threshold?

Fluvius distinguishes between small and large production installations. This distinction determines the level of administration and technical requirements attached to your installation. The threshold is based on the total inverter capacity — the combined output of your solar panels, any battery storage and vehicle-to-grid inverter, linked to a single EAN number.

Up to 25 kVA, no grid study is required and you simply register your installation via My Fluvius. Above 25 kVA, a grid study is mandatory before connection. Above 30 kVA, an external anti-islanding protection device is also required. For installations between 25 and 56 kVA, an accelerated procedure is available whereby Fluvius quickly indicates whether a detailed study is necessary.

Important: for single-phase connections, existing limits continue to apply (max. 5 kVA per phase). The increase to 25 kVA applies to three-phase connections, which are standard for business buildings.

How many solar panels can you install?

In Belgium, inverter capacity is calculated at 85 to 90% of the total peak wattage of your panels. With an inverter capacity of 25 kVA, this translates to approximately 60 to 65 panels of 430–440 Wp — today's standard for commercial installations. Under the old 10 kVA threshold, you were limited to around 26 to 28 panels.

Already have an existing 10 kVA installation? You can expand it by 15 kVA without requesting a new grid study.

Registration requirements: what do you need to do?

Even without a grid study, registration with Fluvius remains mandatory. Every installation must be registered via My Fluvius within three months of commissioning. Failure to do so — or late registration — may result in an administrative charge at inspection. Note that the installer's notification obligation is separate from your own obligation as a customer and grid user: you remain personally responsible. Also bear in mind that Fluvius is currently experiencing a backlog in processing registrations, so plan your installation and commissioning timeline accordingly.

On the cost side, there is good news: since 1 September 2023, Fluvius has used a declaration of honour for anti-islanding protection on large installations up to 400 kVA. A Fluvius technician no longer needs to visit the site, and testing costs are not charged — including for applications already in progress.

Battery storage and EV charging: also within the 25 kVA threshold

The 25 kVA threshold does not apply only to solar panels — the grid injection of battery storage systems falls under the same rules. This makes it considerably easier to combine solar panels, a battery and charging infrastructure without automatically triggering the grid study process.

One important consideration: the total inverter capacity of your installation — solar panels, battery and any V2G inverter combined — must not exceed the 25 kVA threshold if you wish to follow the simplified procedure. Correct system dimensioning is therefore essential.

Why did Fluvius raise the threshold?

The decision is part of the broader energy transition. Businesses and households are increasingly electrifying: heat pumps, EV charging stations, greater self-consumption. The old 10 kVA limit no longer reflected that reality. By raising the threshold, Fluvius aims to lower the barrier to renewable energy while improving network monitoring through mandatory registrations and digital meters.

In summary

No grid study is required for installations up to 25 kVA (three-phase), the installation procedure is faster, and you can install up to 60–65 panels of 430–440 Wp without an additional study. Expanding an existing 10 kVA installation to 25 kVA is permitted, and battery storage and V2G fall under the same threshold. No testing costs for anti-islanding protection up to 400 kVA. Keep in mind that registration via My Fluvius remains mandatory within three months of installation, and that total inverter capacity (PV + battery + V2G) must not exceed 25 kVA.

Powerland guides you from system design to grid connection — including Fluvius registration, any required grid study, and integration with battery storage or charging infrastructure.