Can you become energy independent in Belgium?

Yes, you can become energy independent in Belgium, but not with summer solar alone. In December your panels yield about four times less than in June, while you use more. Full energy independence therefore needs an off-grid system sized for winter: panels, battery, off-grid inverter and a generator. For most homes and businesses the right goal is twofold. Cover a large share of your needs with your own production, and keep running when the grid fails.

You have solar panels, you look at your bill and you wonder why not cut the cord. Or a storm took the grid down, and your panels stopped with it, in full sun. What is harder to see: an installation sized on the whole year falls short in December. And filling that gap with ever more panels costs a lot for one month.

In St-Georges-sur-Meuse, the street had no electricity connection. The farm ran entirely on a generator, day and night. Since the solar panels and battery went in, the generator is only a backup. The system has 30 kVA of charging power and 46.2 kWh of battery, with no street connection at all. In Gedinne, the grid only delivered 180 V instead of 230 V. A semi-off-grid system now supplies 3 x 400 V and uses the weak grid only to charge the battery.

What does energy independence actually mean?

Energy independence can mean three things, and they do not need the same installation:

• Self-consumption rate: the share of your solar output that you use yourself.
• Self-sufficiency rate: the share of your consumption covered by your own production.
• Running without the grid: does your installation keep feeding your circuits during a power cut?

A high self-sufficiency rate does not stop everything from going dark at the first outage. An off-grid installation runs on its own by definition, but it must then also cover the darkest weeks. What sets a real system apart from a plain battery is exactly that: taking over when the grid disappears. What off-grid and semi-off-grid mean, and what the Flemish rules say, is covered in our article on what off-grid means.

Can solar panels make you energy independent in Belgium?

Panels alone cannot: they only produce by day, and very little in winter. Data from PVGIS, the solar tool of the European Commission's Joint Research Centre, shows this clearly. For 1 kWp near Namur (due south, 35°, 14% losses), the average yield swings strongly by month.

Over the year that is about 1,050 kWh per kWp. December brings only about 3% of it, June about 12%. These are multi-year averages: a grey week in December yields clearly less, and that is the week your installation has to survive.

In practice, a solar panel with a battery shifts energy from the day to the evening and night, or covers a few days. It does not carry June's surplus into December. In winter you therefore need the grid, or an auto-start generator. Our article on off-grid solar panels with a battery works out that sizing for the Belgian winter.

Worked example: what does winter change for a home that wants to be independent?

Illustrative example, consumption chosen for the demonstration. A home uses 5,000 kWh a year, of which 550 kWh in December and 330 kWh in June. It installs 10 kWp, due south at 35°, near Namur.

Over the year the home produces twice its consumption, but it is about 240 kWh short in December. Covering December with solar alone would take about 18 kWp, and only for an average month. In an off-grid system you cannot export June's surplus. It is lost, unless it goes to hot water or charging a car.

That is why we size on measured quarter-hour consumption and on the weakest month. Then we decide with you which reserve to use: the grid, a generator or both. With our monitoring software we can measure your consumption for a short period before the installation.

Which options lead to energy independence in Belgium?

Three options lead to energy independence, from light to complete. The choice depends on your connection, your consumption and what must keep running during a power cut.

For many sites, a semi-off-grid system is the best compromise. The public grid only steps in when sun and battery are not enough, and a transfer switch separates both systems. If your home mainly wants to use more of its own power, our home battery page explains the approach. A plug-and-play battery or a portable power station feeds what you plug into it, not your distribution board.

For a business, energy independence often works better than for a home, because consumption falls mainly in daytime. In Incourt, a private school runs fully off-grid, with new panels, a battery and a generator. Our article on a school running on its own electricity tells that story, and the one on off-grid for businesses shows when it pays.

What role does the inverter play in an independent installation?

In an independent installation, the inverter is what makes you independent. A grid-tied inverter follows the grid's voltage and frequency. An off-grid inverter (inverter-charger) forms the local grid itself. It sets voltage and frequency, feeds your loads from the battery and charges it from solar, the grid or a generator.

Technical points to check:

• Switchover time. The Victron MultiPlus-II takes over the loads in less than 20 milliseconds, fast enough for computers to keep running.
• Continuous and peak power. According to the datasheet, the 48/5000 model delivers 4,000 W continuous at 25 °C and 9,000 W peak. Starting currents of compressors and pumps must stay within those limits.
• Two input sources. The Victron Quattro accepts two sources, for example the grid and a generator, and connects automatically to the active one.
• Panel coupling. With AC-coupled solar inverters, Victron applies the factor 1.0 rule. The PV power stays below the continuous power of the inverter-charger at 25 °C.

How long an off-grid inverter keeps going depends mainly on the battery behind it. Our article on the off-grid battery explains how to size it. The one on the off-grid generator with a battery shows how the generator takes over in winter.

Why do your solar panels stop during a power cut?

Because the technical rules require it. Under the Synergrid C10/11 prescription, a connected installation that produces power, battery included, must detect island operation (standard EN 62116) and disconnect. For independent sources up to 30 kVA, the Belgian electrical code (RGIE) allows an automatic separation. It disconnects the installation within 5 seconds when the grid fails.

Without a backup function, your battery and panels therefore stop together with the grid. A real backup battery first separates your circuits from the grid, then feeds them itself.

For a home, our article on the home battery with backup power compares what really works. For a business, our article on a no-break power supply explains how to take over without interruption.

Which rules apply in Flanders, Wallonia and Brussels?

Some rules are federal and apply everywhere, others depend on your region and your grid operator.

• The electrical code applies to everything. An installation fed by an independent source is still an electrical installation under the AREI/RGIE. An accredited body inspects it before it is put into use.
• Switching between sources. Devices that switch sources break all live conductors and must not put the sources in parallel by accident. Synergrid requires "break before make".
• Registration in Flanders. Since 2017 you must register a storage system with Fluvius, with an inspection by an accredited body.
• Declaration in Wallonia. At ORES, declaring decentralised production, batteries included, is a legal duty. Above 10 kVA a deeper study is needed.
• Brussels. The grid operator is Sibelga. Ask it which declaration and documents are needed before commissioning.
• Sharing power with others. Supplying your power to other customers through your own cables is a private network according to the Walloon regulator CWaPE. That is banned in Wallonia in principle, with a few exceptions. In Flanders and Brussels, check with the regulator (VNR, Brugel).