Is your 3x230 V connection too weak? Your options

With a weak 3x230 V connection you have four routes. Choose devices made for 3x230 V, ask your grid operator for 400 V, or add a transformer. Or let a semi-off-grid system make its own 3x400 V from a battery and solar panels, with the grid only as a charger. The first two routes are the cheapest when they are possible. The last one is the answer when the voltage itself is poor, or when 400 V is years or hundreds of metres away.

You ordered a heat pump or a faster charger, and the installer frowns at your meter box: 3x230 V, no neutral. Or the solar quote turns out to be one single-phase inverter that only covers part of the house. Or the lights dim every time the well pump starts. You ask the grid operator for 400 V, and nobody can tell you when, or what it will cost.

That uncertainty costs more than it seems. A device built for 400 V runs at a fraction of its power, or not at all. You end up buying smaller or more expensive versions. And the price of a switch can jump once a cable has to be laid. One new-build owner on the Bouwinfo forum saw an estimate of about 400 euro become an offer of 5,461 euro. It covered 284 metres of cable beyond the first 100 free metres.

A hunting lodge in the woods at Gedinne, in the province of Namur, had a worse problem. Only 180 V was left of the 3x230 V at the house. YouPower installed a semi-off-grid system with solar panels and a battery. It turns that weak line into a stable 3x400 V supply: a 32 A system at 3x400 V with 46.2 kWh of storage. The public grid is still used, but only as a charger, and a generator is connected for power cuts.

What is the difference between 3x230 V and 3x400 V?

Both are three-phase connections. The difference is the neutral, and with it the voltage between the phases.

• 3x230 V (without neutral): three phases, with 230 V between each pair. A normal 230 V appliance is connected between two phases. This older network type is still widespread in Belgium, except in Limburg.
• 3x400 V + N (3N400): three phases and a neutral, with 400 V between the phases and 230 V between each phase and the neutral. ORES, for example, no longer builds new 3x230 V circuits.

At the same fuse, 3x400 V + N delivers about 1.7 times more power. That is the square root of 3, because the voltage between the phases is higher.

That is why the standard Fluvius connection differs per street. On a 230 V network it is three-phase 40 A, with 15.9 kW. On a 400 V network it is three-phase 25 A, with 17.3 kW.

How do you know if you have 3x230 V or 3x400 V?

You cannot choose it yourself. It depends on the network in your street, and there are three easy ways to find out.

• Ask your electrician to check the main breaker. A main breaker with a neutral usually means 3x400 V + N; three phases without a neutral means 3x230 V.
• Use the grid operator's tools. In Flanders, Fluvius has an online voltage checker for your street. In Wallonia and Brussels, ask ORES, RESA or Sibelga for your address.
• Measure between two phases. Around 400 V means 3x400 V + N; around 230 V means 3x230 V. Leave this to a qualified electrician.

Why do heat pumps, EV chargers and inverters struggle on 3x230 V?

Much three-phase equipment is designed for 3x400 V + N. On a 3x230 V network you need a version made for it, a single-phase version, or a way to create 400 V.

• Solar inverters. Single-phase inverters work on 3x230 V. A three-phase inverter built for 400 V would lose a factor of about 1.7 in output. So installers combine several single-phase units or add a transformer. Your inverter can also trip when the voltage runs too high.
• EV chargers. Single-phase charging stops at about 7.4 kW. 11 kW needs three phases at 400 V and 16 A. Without a neutral, some cars have charging problems, so check with the car maker first.
• Heat pumps. Larger heat pumps often need a three-phase supply because of their start-up power. Most equipment exists in single-phase and three-phase versions, but check that the model you want exists for 3x230 V. For a workshop or warehouse, see whether your business connection can handle a heat pump.
• Home batteries. There are fewer battery inverters for 3x230 V. In Beveren, a 15.4 kWh home battery was connected single-phase because the street only offers 3x230 V.
• Motors and pumps. A heavy machine that starts on a weak line pulls the voltage down for everyone on it. Here is how to get more power for a new pump or machine.

Why is the voltage on my 3x230 V line too low?

The voltage at your meter has to stay within 230 V plus or minus 10%, so between 207 and 253 V. On long, old rural lines it can drop below that when everyone uses power at once.

Low voltage is the grid operator's problem to solve, so report it. ORES, for example, has about 1,000 voltage regulators on long low-voltage networks of more than 800 metres. It is also setting deadlines for its answer to voltage complaints. But a fix in the street can take time, and it does not give you 400 V.

Gedinne shows how far it can go: 180 V instead of 230 V, well below the legal minimum. Motors, compressors and electronics do not like that. A battery system that forms its own voltage on site takes that problem away, because your devices no longer run directly on the weak line.

Can you switch from 3x230 V to 3x400 V?

Often you can, but the price and the wait depend on the network in your street.

In Flanders: Fluvius

Fluvius publishes fixed 2026 prices for 400 V on request when you are on a 230 V network. These prices apply to a single connection when the power is available. Work on your own installation comes on top.

When Fluvius converts a street to 400 V as part of its own network plans, it does not charge the surcharge for 400 V on request. The forum example above shows the other side: when new cable has to reach your plot, the bill can grow to several thousand euro.

In Wallonia: ORES and RESA

ORES no longer builds new 3x230 V circuits and converts its old 230 V networks step by step. It starts with areas where heat pumps and electric cars will grow fastest, such as the edges of towns. How it converts depends on the age of the network:

• Older than 50 years: the network is replaced by a 3x400 V + N network and all customers are converted.
• 25 to 50 years: a new 400 V cable is laid next to the old one. Customers move over one by one, when they ask for it, until the old cable can be taken out.
• Younger than 25 years: the network is already suitable and is converted in one go.

Ask ORES or RESA what is planned for your street and what a switch would cost at your address. The Walloon energy minister said it plainly in 2023. Customers who add new electrical equipment sometimes have to ask for a stronger connection, and that is paid.

What are your options with a weak 3x230 V connection?

Put the four routes next to what your problem really is: one device, too little power, or a voltage that is too low.

How does a semi-off-grid system make 3x400 V from a weak grid?

In a semi-off-grid system your site runs on its own island grid: solar panels, a battery and inverters that form a stable three-phase supply. The public grid stays connected, but only to charge the battery when the sun is not enough.

Your devices no longer see the weak line, they see the voltage the inverters make. That is why the route also works where the grid is too weak for a heat pump or a machine. If the public grid fails, the system keeps your site running. The same idea helps businesses that cannot get a heavier connection.

Where you want to stay closer to the grid, a home battery can also work on 3x230 V, as in Beveren. It is a smaller step, but it does not create 400 V.

What happens when you contact YouPower?

It starts with your connection and your numbers. From there, one team takes you from the first calculation to a working system.

• You send what you have. Your connection type, the voltage you measure if you know it, the device you want to add, and your yearly use in kWh. The quotation form asks for that yearly use.
• We measure where we can. Actual and peak consumption size everything, from battery to inverters and cables.
• Our engineering office calculates the system. The panels, the inverters, the battery and, if needed, a generator.
• We build, test and commission it. We carry out the entire installation, test it and put it into service.
• We keep following it. You follow the system in real time in the app, with alerts on your phone. Our after-sales service follows up, and we are reachable 24/7.