Flood-prone area: where do the battery and inverter go?

Put the battery, the inverter and the main switchboard on a level that the water will not reach. In a flood-prone house that rarely means the cellar, where a home battery often ends up because the meter is there. Check your flood score first, then split the circuits so the floodable rooms can be switched off on their own.

You live or work in a river valley, and you remember the water. Maybe it was the Vesdre in July 2021, or the Dender and the Demer in November 2010. Now a quote for a battery puts it in the cellar, next to the meter, because the cables are shortest there. A Belgian owner on Reddit keeps his batteries in a detached garage, not in the basement. There, he wrote, "I would also have to worry about what happens during a potential once-in-a-lifetime flooding".

That instinct is right, and the problem is bigger than one appliance. In a flood, the battery, the inverter and the switchboard go under together. Your back-up then fails exactly when the power is cut. A family in a Flemish government brochure had 1.60 m of water in the house; afterwards their electrical installation "had a lot of damage". A lithium battery that sat in that water is no longer a device to dry out. It is a damaged battery that needs a specialist.

Is your home or site in a flood-prone area?

Look it up on the official map of your region before you decide where anything goes. The maps are free and work per plot.

In Flanders, score A means no flooding is modelled. B is a small chance with the climate of 2050, C a small chance today and D a medium chance today. The worst of the three flood sources sets the score. Since 1 January 2023, sellers must mention these scores in ads and deeds, and so must landlords of leases over nine years.

In Wallonia, the hazard map was adopted on 4 March 2021, a few months before the floods. The Region says it will be revised, partly because of the works in the valleys hit in 2021. Five years on, it is still rebuilding along the Vesdre, with fourteen large works under way or starting in 2026.

Along the Dender and the Demer, the Flemish river basin teams mapped the floods of November 2010. The Dender basin flooded again in January and in May and June 2016. A score or a hazard level is a starting point. Your own memory of where the water came in is just as useful.

Where should the battery, inverter and switchboard go in a flood-prone house?

On the highest practical level that is still dry, close enough to the main board, and away from bedrooms and escape routes. Flood safety and fire safety point to the same spot more often than you think.

The Walloon guide on existing buildings is clear: the switchboard and the meter "must be installed on levels that do not flood". The Flemish environment agency (VMM) says the same: move the installation above the expected water line where possible. Battery makers agree. The SolarEdge home battery manual says: "Install the battery in a location protected from flooding."

The loft is the trap. It is the driest place in the house, but British fire guidance (PAS 63100) keeps batteries out of lofts and roof spaces. So the answer is usually a raised technical room or a half level, not the top of the house. Read more in our article on the fire risk of a large home battery. If the only dry spot is outside, check what a home battery needs to stand outside.

Does an IP rating protect a battery against a flood?

No, not the ratings you see on home batteries. IP55 or IP65 means protection against water jets, not against standing water.

The second digit of the IP code shows how well a housing keeps out water. The VMM brochure explains it: IP-x7 is "immersion-tight" for water up to 1 m for 30 minutes. Only IP-x8 counts as waterproof for longer or deeper water. A flood in a valley often lasts hours and carries mud.

Manufacturers draw the same line. "Do not immerse the battery or its components in water or other fluids," warns the SolarEdge manual. A battery rated for outdoor use is made for rain, not for a flood.

How do you split the circuits so the dry part keeps running?

Give the floodable rooms their own circuits, with their own residual current device, and switch them off in one move. The rest of the house then keeps its power.

The Walloon guide lists the steps. Circuits in rooms that can flood are separated from the upper floors. The switch for the lower circuit gets a clear label. Wiring on the lowest floor runs along the ceiling, sockets sit high, and those circuits get a residual current device.

The VMM adds one important rule. Appliances that must not fail, such as freezers, detection systems and central heating, do not go on the floodable circuits. That list is close to the list of loads you want on battery back-up in a power cut. Read how a full no-break house is wired, with a separate back-up board. Or start with the basics of a home battery with backup power.

A sump pump is the exception: it sits low by nature. The VMM advises placing the power contact of a pit pump above the expected water level. Which pumps belong on battery back-up is in our article on pumps in a power cut.

What about farms and business sites in a flood zone?

The same logic applies at a larger scale: keep the battery container, the inverters and the main board out of the water's path. In Wallonia, the permit file for a solar project asks for it.

A Walloon fact sheet for solar projects rates electrical cabins, "including batteries, inverters and PCS", as medium vulnerability to runoff floods. Farm equipment, stables and poultry houses rate high. The measures it lists include:

• Placing buildings, electrical cabins and batteries with care.
• Moving the vulnerable element out of the main runoff path.
• Raising openings and floor levels above the possible water heights.
• Guiding the water around the element with ditches, earth banks or swales.

In Wallonia, a building permit in a flood hazard zone goes to the flood services for advice. The municipality can then refuse it or add conditions. In Flanders, the water test in the permit does the same job. For a solar field next to the farm, see which permit a ground-mounted solar installation needs. For the choice between a container and a room, see battery container or technical room. A business battery in a container can also stand on a raised plinth, above the water line.

What do you do if the water reached the battery anyway?

Do not switch it back on, and treat it as a damaged lithium battery. The installation also needs a check before it goes live again.

1. Step 1: Never walk through water to reach the switchboard. If you cannot reach it from a dry place, call the fire service.
2. Step 2: Leave the battery off and keep people away from it. Call your installer, and do not open or dry the battery yourself.
3. Step 3: Have the electrical installation checked and repaired by a professional. After changes, the Walloon guide notes that an approved inspection body must accept the work.
4. Step 4: Hand in a battery that cannot be saved to a specialist. Our Battery Disassembly Center takes in damaged lithium batteries, including home batteries, and checks the cells before dismantling.

For companies with several damaged batteries, read how to store a damaged lithium battery safely. Tell your insurer what was damaged, and keep photos.

Does a flood zone change your insurance or the sale of your house?

It can, so check before you build or buy. Flood-prone areas and insurance risk zones are not the same thing.

Risk zones for flooding are part of the natural disaster insurance and are smaller than the flood-prone areas. In those zones, insurers may ask a higher premium and may refuse flood cover for new buildings. In Wallonia, the risk zones match the areas with a high flood hazard on the map. In Flanders, a recognised expert can update the P-score and G-score after flood-proofing works.

How do we plan a battery in a flood-prone home?

We start with the water, then the electricity. Our team has three certified battery experts, and we also revise batteries that are already installed.

1. Step 1: We look at your flood score or hazard level, and ask where the water came in before.
2. Step 2: We choose a dry spot for the battery, the inverter and the back-up board, and plan the cable route to the main board.
3. Step 3: We connect your main systems separately to the battery, so the household keeps running in a power cut. In Wetteren, the whole house runs on the battery this way.
4. Step 4: You follow the system from anywhere in the free VRM app and portal. After a storm, you can check from a distance whether it still runs.