What can a business do about a solar export limit?

An export limit means your solar panels may no longer feed power into the distribution grid, or no more than a fixed amount. With zero export, that limit is zero. A business ends up there in three ways. The grid operator imposes it after a grid study. The grid voltage rises so high that the inverters switch off. Or export earns nothing at certain moments, or even costs money. Curtailing solves the problem but throws energy away. If you want to use the surplus, shift consumption to midday or store it in a business battery. The right mix follows from your measured quarter-hour data.

It usually starts with a letter or a number. The grid study caps your export, the inverters drop out on the sunniest afternoons, or the energy bill shows you paid to export on a Sunday. The hidden cost: every kWh you curtail, or export at a negative price, is a kWh you buy back on Monday morning. Often that is exactly the moment your quarter-hour peak is set.

Why would a business limit its solar export?

Export earns nothing more and more often. According to the CREG, the Belgian regulator, the day-ahead price in Belgium was negative for more than 520 hours in 2025, 27.5% more than in 2024. The CREG names the strong growth of solar power as the main cause. Those hours typically fall on sunny middays with low demand: exactly when a business is closed at the weekend and the roof produces at full power. With a contract that passes on the market price, you pay to export at those moments. What that means for payback is in our article on whether solar panels still pay off on a business roof.

The grid operator sets a limit. For larger installations, the grid study can fix an export limit. In Flanders, Fluvius can also temporarily limit the export of large production installations in areas with grid congestion.

The inverters switch off on their own. An inverter must disconnect when the voltage gets too high. According to Synergrid C10/11, the Belgian technical rule, the automatic disconnection system trips at 230 V + 10% as an average over 10 minutes. At 230 V + 15% it disconnects without delay. On a part of the grid with many solar panels you hit that limit sooner, and then you lose all of your production instead of part of it. In Wallonia you can report tripping inverters to ORES with its online form. Read more in our article on why a solar inverter trips when the grid voltage is too high.

What is the difference between a feed-in tariff and a grid injection tariff?

In everyday speech, both mean the same thing: the price your energy supplier pays you per kWh you export. That price is set in your supply contract. With a fixed contract it is fixed; with a variable contract it follows a market index at set intervals. With a contract that passes on the market price per quarter hour or per hour, it can turn negative at certain moments.

Strictly speaking, there is also a grid operator's injection tariff: a grid charge for using the grid when you export. In Flanders, the 2026 tariff list of Fluvius Antwerpen, published by the Flemish regulator (Vlaamse Nutsregulator), puts it at about 0.18 cent per kWh (excluding VAT). It applies to export customers with peak metering or on a higher voltage level. Grid users with distributed production up to and including 10 kVA do not pay it. The amounts differ per grid area, and Wallonia and Brussels have their own tariff lists.

Two other points matter for a business with solar panels:

• For the Flemish capacity tariff, only your offtake peaks count, not your export peaks, according to the Vlaamse Nutsregulator.
• Fluvius studied time-of-use grid tariffs, including for export. In its report of August 2025, Fluvius takes a wait-and-see approach to export for now. Keep an eye on it, because it can change the calculation later.

When does the grid operator impose an export limit?

That depends on the size of your installation and on your region:

• Flanders: according to Fluvius, you register an installation up to 25 kVA through Mijn Fluvius. For installations from 25 to 56 kVA you first request a grid study.
• Wallonia: a small production installation goes up to 10 kVA of inverter power (AC). According to Energie Wallonie, a larger installation is not forbidden, but it follows the normal procedure with a grid study by the grid operator (ORES or RESA), which decides how much you may export.
• Brussels: check the technical requirements of Sibelga before you add panels or a battery.

The grid operator's study also states any limit on the power you may export. C10/11 allows the operator to impose an export limitation relay of a type approved by Synergrid (list C10/25). There are two variants:

How does zero export work technically?

Zero export is a control loop. A meter at the connection point measures in which direction and how much power flows. Based on that, the energy management system turns the solar inverters down, charges the battery or switches on loads.

As soon as the installation includes a battery, C10/11 requires a power management system that never lets export exceed a set limit. The requirements are specific:

• the measurement is taken where the combined power of all production units can be measured;
• an EnFluRi sensor or another direction-sensitive meter measures and reports at least every 500 milliseconds;
• if the measurement fails, the system must react within one minute so that the export limit is not exceeded, if need be by stopping export;
• after a step change, the deviation must drop below 10% of the starting value within 3 seconds;
• for installations that are not small production installations, the P1 port of the digital meter may not serve as the measurement source.

Victron systems do this with ESS, which runs on the GX device. According to the ESS manual of Victron Energy, solar export can be switched off completely or capped. A grid setpoint just above 0 W keeps the control on the offtake side. The manual also warns that the limit can be exceeded briefly when a large load drops away or production jumps. According to Victron, zero export with AC-coupled inverters has mainly been tested with Fronius. So the choice of components and the tuning make the difference. Control too slowly and the relay trips. Control too tightly and you draw power from the grid for nothing.

What are your options with an export limit?

Shifting loads can be simple. A farm in Tielt uses smart control to send surplus solar power to its boilers.

The last option belongs with a contract that passes on the market price. Since 1 October 2025, the Belgian day-ahead price is calculated per quarter hour according to the CREG, so the control must be able to work at that rhythm. Do you have such a contract, or are you considering one? Then read our article on a dynamic energy contract with a battery for businesses to see how it works together with storage.

How much solar surplus can you use yourself with zero export?

Take a worked example with illustrative figures. A manufacturing business has 100 kWp on the roof. On a sunny Saturday in May, the installation produces about 360 kWh in total between 10:00 and 16:00. The business is closed and uses 60 kWh in that period (cooling and IT). The surplus is therefore 300 kWh. Assume the market price is negative between 12:00 and 16:00.

In the last scenario, 160 kWh of the 300 goes to self-consumption. The battery delivers those 100 kWh on Monday during start-up, exactly when the quarter-hour peak is set. So the same kWh works twice: less offtake and a lower peak. Want to know what that lower peak is worth? Then read our article on calculating the capacity tariff for businesses in Flanders to convert the peak into euros.

When is a battery better than curtailment?

Curtailing is enough when the surplus is small and rare. A battery becomes interesting when:

• the quarter-hour data show a structural surplus, for example every weekend or every midday in the summer half of the year;
• you also have a high quarter-hour peak that a battery can flatten;
• the grid operator imposes a low export limit and you still want to install more panels;
• business continuity matters and a power cut causes real damage.

Never start from the power of the panels alone. Put production and consumption per quarter hour side by side, over a full season. We can monitor your consumption in advance, and after installation you follow the system through the monitoring software. If you want to go further, a semi off-grid system lets you draw as little power from the grid as possible.