The first useful solar question is not how many panels fit on a roof. It is when the home uses electricity. In France, a household that is often out during sunny daytime hours may use a different share of its own production from one with daytime heating, cooling, or regular appliance use.
Start with your consumption pattern
Look at electricity bills and, where available, the consumption data from your supplier’s customer account. Note recurring daytime loads such as a heat pump, water heating, or home working, as well as appliances that could be scheduled safely during daylight. These observations are more useful than assuming that annual consumption alone will determine the right system.
Compare the roof and the proposal
Ask installers to explain how roof orientation, shading, usable area, and system design shape their production estimate. Compare proposals using the same assumptions, and ask what is included: equipment, electrical work, monitoring, and any changes to the roof. An estimate is a projection, not a guarantee of output or savings.
Battery storage is another decision, not an automatic part of a solar installation. Its usefulness depends on the timing of production and consumption, the proposed system, and its cost over the period you expect to use it. Ask for a comparison with and without storage, using the same stated assumptions.
Verify terms before signing
Before committing, check current rules and any financial support through official French sources, including service-public.fr and the relevant energy information channels. Conditions, required steps, and applicable dates can vary, so confirm them for your situation rather than relying on an old article or a sales presentation. Keep a copy of the source and date you consulted.
A sound comparison connects the roof, household routine, equipment, and contract terms. Ask each installer to show how those pieces fit together and which assumptions drive the estimate. If the explanation does not make sense without a promised return, pause and get another proposal.