Glossary
Onduleur: the solar inverter in a PV installation
What is an onduleur?
An onduleur is the inverter in a solar installation. Panels produce direct current, and your appliances and the grid run on alternating current, so the onduleur converts one into the other. It's on every solar PV quote. It's also usually the first part of the system that needs replacing, so its type and warranty deserve a look before you sign.
String inverter or micro-inverters: which suits your roof?
This is the main choice you'll see on a quote, and shade decides it.
- String inverter (onduleur central): one box, usually in the garage or loft, with the panels wired to it in a chain. It's the cheaper option and easy to replace. Its weakness is shade: if one panel is shaded by a chimney, a pine or a neighbour's wall, the whole chain produces less. It suits an open roof where every panel gets the same sun.
- Micro-inverters (micro-onduleurs): a small unit behind each panel. Each panel works on its own, so shade on one doesn't pull down the rest. They cost more, and they suit roofs with several slopes, nearby trees or chimneys. You can also see each panel's output in the monitoring app.
- String inverter with optimisers (optimiseurs de puissance): a middle route. A small optimiser on each panel limits the shade loss, and a central box does the conversion. It usually costs less than micro-inverters.
Ask the installer which of these they propose and why. If your roof has shade at some hour of the day, ask how much output the chosen setup loses to it.
Do you need a hybrid onduleur for a battery?
A hybrid onduleur (onduleur hybride) can also charge and run a home battery. You need one if you want a battery now, or if you want to add one later without replacing the onduleur. Exported surplus now earns only 1.1 c EUR per kWh, so each unit you store and use in the evening is worth far more than selling it. Ask whether the model on your quote is battery-ready.
Watch the invoice if you buy the battery at the same time. A battery quoted on the same job as the panels puts the whole invoice at 20% TVA (French VAT). Ask for the panels and the battery to be priced as separate jobs.
What to ask about the onduleur on a solar devis
- Make and model: the exact model should be named, since it goes on the Enedis connection request. Established brands are already approved for the French grid. An unfamiliar brand can hold up the connection, so ask the installer whether they've connected that model before.
- Size: ask whether the onduleur is matched to the panels. A slightly smaller one is normal. One much smaller than the panel array wastes output on the sunniest days.
- Warranty: ask how many years it runs, and compare the figure across your two devis (written quotes). Since this is the part most likely to fail, a longer warranty here matters more than on the panels.
- Monitoring: most models come with an app that shows daily production. For a second home, it's how you'll spot a fault while you're away.
How long does a solar onduleur last?
Solar panels are warranted for decades. An onduleur usually lasts 10 to 15 years, so plan on replacing it at least once over the life of the system. Count that cost in when you work out payback. A string inverter is a single swap. Micro-inverters cost more to replace one by one, but when one fails the rest of the roof keeps producing.
More on solar panels, batteries and the grid
Sources
Official sources for solar onduleur and battery rules
- BOFiP: BOI-TVA-LIQ-30-20-97, TVA on solar electricity equipment A battery quoted on the same job as the panels and onduleur puts the whole invoice at 20% TVA.
- Légifrance: arrêté of 1 June 2026 on small solar installations The 1.1 c EUR per kWh paid for exported surplus, which is why a battery-ready onduleur is worth asking about.
- Enedis The grid operator that receives the connection request, including the onduleur model, before a system can export.
Rules checked against these sources in September 2026.