Everything to know before, during
and after your simulation.

Yes, completely, and without creating an account. The whole tool is free for households: the full simulation (annual generation, self-consumption rate, savings, financial return), but also the power optimisation slider, the interactive monthly generation charts, the comparative home battery scenarios, the 25-year financial projection tables with NPV and IRR, and the detailed report. No paid service is offered to households.

No. On calcul-solaire.fr, the simulation and the full report are free, with no account, no e-mail and no phone number. No simulation or contact details are passed on to an installer or sold, and the site takes no commission (privacy policy, sections 3 and 7). That is the whole point of the project: to give you a neutral, reference-grade tool, without sales pressure.

Yes, in metropolitan France. The three RT2012 climate zones are supported: H1 (north, Île-de-France, Alsace…), H2 (centre-west, Atlantic coast, Rhône-Alpes…) and H3 (Provence-Alpes-Côte d'Azur, Languedoc, Corsica…), with PVGIS data specific to each municipality. Corsica is included. The French overseas departments (DOM) are not covered yet.

No. The simulation needs no sign-up, no e-mail address, no password and no bank card. You can run a new simulation at any time, and the full report is available immediately.

The simulator uses satellite data from PVGIS (Photovoltaic Geographical Information System), the European Commission's reference database for solar irradiance. Calculations are carried out hour by hour (8,760 steps over a year) and take into account the French climate zone (H1, H2, H3) and the orientation and tilt of the roof, before being matched against a personalised consumption profile modelled on your situation.

The margin of error on annual generation is typically ±5% compared with a real installation under nominal conditions. Accuracy depends above all on the quality of the parameters entered: the actual orientation of the roof (a 10° error means a gap of about 2%), partial shading that has not been declared, and actual consumption compared with the modelled profile. The large gaps seen against installers' quotes usually come from different calculation methods, not from errors in the tool.

The solar irradiance data comes exclusively from PVGIS v5.3 (Joint Research Centre, European Commission). The simulator calls the PVGIS /tmy API (Typical Meteorological Year) to obtain the 8,760 hours of radiation of a typical year for the GPS coordinates of the project. This data is recognised as the reference standard for residential photovoltaic studies in Europe.

Yes. You can enter an estimated shading percentage yourself and, when you refine your study, the simulator combines the PVGIS data with Google Solar to estimate the impact of shading on your hourly generation, based on your address and the layout of your roof. It is an approximation that can be refined with a shading survey carried out on site by a professional, but it already lets you include a shading estimate in the simulation without any extra effort on your part.

The self-consumption rate measures the share of your solar generation that you use directly, without it going through the grid. A rate of 70% means that 70% of the electricity produced by your panels is used at the moment it is generated. This rate is decisive for the financial return: every kWh you self-consume is worth the grid purchase price (e.g. 0.2001 €/kWh on 1 August 2026), whereas the surplus you sell earns far less (0.011 €/kWh under the EDF OA feed-in tariff). A high rate therefore improves the payback significantly.

Both can be correct and still differ. Common reasons for a gap: (1) the installer uses proprietary software (PVSyst, Sunny Design) with different assumptions about degradation, cable losses or inverter efficiency; (2) the installer proposes a different peak power; (3) the reference weather data differ (PVGIS versus a local Météo-France database). A gap of ±10% is normal. Beyond that, ask the installer to share the assumptions behind their calculation. Feel free to contact us with any question about interpreting the results or the gaps you have found.

For two reasons related to the financial return. First, an oversized installation produces a large surplus that will be sold at a rate below the grid purchase price, which worsens the payback. Second, beyond a certain size each extra kWp produces little but surplus, bought back at a very low rate: the economic optimum can lie below the physical maximum. The simulator optimises the power to maximise the net saving over 25 years, not just the gross generation.

Yes. The simulator models self-consumption with and without a home battery, estimates the self-consumption rate, the surplus exported to the grid and the share consumed, and suggests an optimal capacity for your profile. You get a detailed comparison of 5 battery sizes (5, 7.5, 10, 12.5 and 15 kWh) plus a customisable field, showing for each one: the self-consumption rate, the gain in self-consumption, the additional annual saving, the estimated cost including VAT, the annual cycles and the incremental payback.

Everything, with no conditions: installation power, annual generation, self-consumption and self-sufficiency rates, estimated savings, payback period, but also the interactive power optimiser that calculates according to your own criteria, the charts of monthly generation compared with your consumption, the home battery options, appliance scheduling, the virtual battery, the 25-year financial projection with annual cash flows, NPV and IRR, and the detailed report that you can download.

No. No payment, no subscription and no bank card is asked of households, and your simulation is not passed on to anyone.

Yes, and it is one of the most useful ways to use the tool. If an installer has given you a quote, you can enter the real cost of the installation to get personalised financial projections: payback period, NPV and IRR recalculated from your actual quote rather than the estimated cost. This lets you judge objectively whether the quote you have been given is worth it.

The full report, of around fifteen pages, is designed to be readable and credible in a financing application. It includes: the project summary (power, generation, climate zone), the detailed consumption profile, the monthly generation chart, the home battery scenarios, the 25-year financial projection with NPV and IRR, the LCOE, the environmental impact, and a glossary. It is, however, produced by an online tool rather than by an accredited engineering firm: some banks or lenders may require a further study signed by a professional.

It is a complex question, as every house has its own characteristics and different appliances that use electricity. The simplest thing is to run a simulation. The simulator calculates the optimal power for your consumption profile, your area and your orientation, according to the goal of your project.

Self-consumption with sale of the surplus is the most common. You use what you produce first, and when there is a surplus (in summer, for example), you sell it to EDF OA at the regulated rate (0.011 €/kWh since the ministerial order (arrêté) of 1 June 2026). Full (or “pure”) self-consumption: you use what you produce, but you sell nothing when there is a surplus, which is fed back into the grid free of charge (or stored or credited if you have a home battery or a virtual battery). It suits small installations (plug-and-play kits) or if you do not want to deal with Enedis, the grid operator. Full export: 100% of the generation is sold to EDF OA (0.011 €/kWh for an installation of 9 to 36 kWp), and you keep buying 100% of your consumption from the grid.

No. calcul-solaire.fr is an independent simulation tool with no commercial partnership with installers. After your simulation you have objective data (recommended power, expected generation, indicative budget) to request and compare several quotes from RGE-certified installers (the French quality label for renovation professionals).

In 2026, the main support is the reduced 5.5%% VAT rate for systems ≤ 9 kWp on a dwelling, whatever its age (instead of 20%%). The self-consumption bonus (prime à l'autoconsommation) was abolished by the ministerial order (arrêté) of 1 June 2026.

It takes the reduced 5.5%% VAT rate into account when the installation is eligible (≤ 9 kWp, conditions met). As the self-consumption bonus was abolished on 1 June 2026, no bonus is deducted: the net cost is the installation cost including VAT, and that is what feeds into the payback and LCOE (cost per kWh produced) calculations.

A general payback period is hard to state without knowing your profile. But to give an order of magnitude, for a well-sized residential installation in 2026, the payback period would probably be somewhere between 8 and 12 years depending on the geographical area, the orientation of the roof, the price of grid electricity and the self-consumption rate. In zone H3 (southern France) with a due-south orientation and a well-sized installation, the payback is often under 9 years. In zone H1 with an east/west orientation, it can exceed 12 years. The simulation calculates your personalised payback from all these parameters.

For installations of up to 3 kWp that produce only for self-consumption, the income is exempt. For installations that sell the surplus: if the power is up to 3 kWp AND you are a private individual on your main residence, the sales income is exempt from tax. Above 3 kWp, the sales income falls under the micro-BIC regime (the simplified French tax regime for small business income) with a flat-rate allowance of 71%. Above 9 kWp, you leave the private-individual regime. These are the rules in force in 2026; check with your tax adviser for your exact situation.