CESI: the solar water heater for a single home

Does a CESI make electricity like solar panels?

No. A CESI makes hot water only. Solar panels (photovoltaic, or PV) make electricity, which can run the whole house and feed the grid. They use different installers and different grants, so a quote for one tells you nothing about the other. If a salesperson says "solar" without saying which, ask which before anything else.

How much hot water does a CESI supply on the Côte d'Azur?

The sun does most of the work for much of the year here. In winter the backup takes over, so the tank still heats on grey days. An installer who promises an exact percentage without having seen your roof and your household is guessing, so ask how they sized the system.

Does a CESI need a déclaration préalable?

Yes. Collectors on a roof are visible, so they need a déclaration préalable (a simple planning notice filed with the mairie, the town hall) like any other roof equipment. Near a listed building or in a protected area, the ABF (the heritage architect) has a say, and may ask for a different position or finish. Ask your installer whether they file it for you.

Which grants pay for a CESI, and which have ended?

MaPrimeRénov'. The state grant for energy renovation dropped solar water heaters from its single-measure route on 1 September 2026. Now it pays only inside a rénovation d'ampleur (a whole-house renovation), and only for a main home. Second homes don't qualify. See MaPrimeRénov'.

CEE. The CEE (energy savings certificates, paid by energy suppliers) have no residence condition, so they work for a second home. Sunshine counts in the sum, so the Côte d'Azur gets one of the better amounts for a solar water heater. On a devis (written quote) signed before 1 January 2027, the amount is four or five times its usual size, but only if no gas or oil heating or hot water equipment is installed or kept in the home. Amounts vary between energy suppliers, so compare offers and accept one before you sign the devis.

Département des Alpes-Maritimes. The Département pays 25% of the cost before tax, up to about 1,000 EUR. The collectors must cover at least 2 m², the installer must hold RGE certification (the state's approved-installer label), and there's no income condition. It's for owners who live in the house as their main home, and for landlords, so a second home you keep for yourself doesn't qualify. You claim after the work: the application goes in once the system is fitted, within six months of the invoice.

TVA. French VAT on a CESI is 5.5%, because it counts as energy renovation in a home more than two years old. The TVA entry explains the conditions.

What should you ask a CESI installer before signing?

For CEE and the Département grant, the installer needs RGE certification, specifically the QualiSol label for solar thermal work. Ask for the RGE number to be printed on the devis. With two devis in hand, compare what each one includes as well as the price.

Put four questions to them. Who files the déclaration préalable? Is the backup electric or gas, given what that does to the CEE bonus? How was the system sized for the people who live in the house? Which grants has the devis already allowed for? The CEE offer from the energy supplier has to be accepted before you sign, so get it in writing first.

More on solar water heating and French grants

• Solar water heating on the Côte d'Azur
• CEE energy savings certificates
• Rénovation d'ampleur