Projectcalcul-solaire.fr
Calculation notes
DataPVGIS 5.3
CalculationHour by hour · 8,760 h
Weather at your address
- Where it comes from
- PVGIS 5.3, the European Commission's Joint Research Centre. A typical weather year of 8,760 hours (irradiation, temperature, wind) for your coordinates (data shared for 30 days with neighbouring addresses within about one kilometre).
- How it is calculated
- Irradiation is converted to the plane of your panels, then cell temperature is calculated with the NOCT model. Nothing is smoothed to monthly values.
- What you can do
- Your address, or the point placed on the map, sets the location.
- Limit
- The weather data carries its own uncertainty of about ±5%.
Your roof and the number of panels
- Where it comes from
- The roof faces (area, orientation, pitch) come from your drawing.
- How it is calculated
- The number of panels is measured: the panel layout actually places modules on each roof face, with a 0.30 m setback from the edge, rather than dividing an area by a flat allowance.
- What you can do
- You can correct the drawing, the dimensions and the exclusion zones. Your dimensions are authoritative.
- Limit
- A roof with more than four faces is cut down to the four faces carrying the largest share of the capacity.
Shading on your roof
- Where it comes from
- IGN HD LiDAR: a surface model at 0.5 m resolution, from a dated airborne laser survey. Free, and used from the first calculation. Google Solar is used as a complement where the LiDAR does not cover certain data.
- How it is calculated
- Without a drawn outline, the area studied is the building footprint from the IGN BD TOPO. From each point of each roof face, a ray is traced towards the sun for every month and every hour. The share of unobstructed rays gives a mask of 12 months × 24 hours, applied to the direct component only.
- What you can do
- You can ignore vegetation, count deciduous trees, or impose your own shading loss in %. The measured survey stays displayed beside it.
- Limit
- The survey is dated: a tree planted or felled since then does not appear. The winter shade of deciduous trees is overestimated. Outside the coverage, the factor you declare applies.
Your electricity consumption
- Where it comes from
- A measurement always takes priority over the model: meter curve or monthly readings first, otherwise the calculator total, otherwise a typical profile. 2021 energy performance certificate (DPE) scale and the 2016 ADEME/COSTIC guide for hot water.
- How it is calculated
- It depends on what you provide. With your monthly readings, heating is measured (regression on heating degree days). With the calculator, it is deduced: the other uses that the calculator already counts are subtracted from the DPE envelope. With a single total, it is split using ADEME statistical ratios. The hourly profile is built from your presence habits and the hours entered in this consumption form.
- What you can do
- Entering your 12 months of readings sets the level of each month. A meter curve replaces the model.
- Limit
- Without readings or consumption data, consumption remains an estimate, which can differ by about ±20% from your actual consumption.
Orientation and tilt
- Where it comes from
- Your drawing gives the azimuth and pitch of each roof face. The values you set here replace them.
- How it is calculated
- Solar radiation from the weather data is transposed onto the tilted plane of your panels (Hay-Davies model, ground albedo of 0.20), hour by hour.
- What you can do
- Adjust the needle and the pitch if needed: the production calculation follows immediately.
- Limit
- A poorly oriented roof face loses output, but an east/west roof flattens the curve and can therefore improve self-consumption.
Annual production
- Where it comes from
- Calculated for 1 kWp over the 8,760 hours of the year, then multiplied by the chosen capacity.
- How it is calculated
- Irradiation on the plane of the panels, performance ratio, temperature correction, hourly shading, inverter efficiency. Each step is detailed in the technical documentation.
- What you can do
- You can impose a production figure or a shading loss. Your value is applied and the calculated value remains visible.
- Limit
- A typical weather year is not a real year: the production of a given year varies, and these are not weather forecasts.
Share consumed on site
- Where it comes from
- Your hourly consumption profile set against the production, over 8,760 hours per year.
- How it is calculated
- Each hour, the share consumed on site is compared with the share produced. The remainder (the production surplus) is exported to the grid. It is not a fixed ratio of 60 or 70%. Two rates follow: self-consumption (the share of what you produce that is consumed on site) and coverage (the share of your needs covered by solar).
- What you can do
- Shifting an appliance to the sunny hours or adding a battery changes these rates.
- Limit
- Without a meter curve, the time of day when you consume remains estimated from your occupancy profile. The accuracy of the simulator and of the data entered helps minimise the error of this estimate.
Savings in the first year
- Where it comes from
- The price of electricity you pay your supplier, depending on your option: Base (price depending on your meter's capacity), Peak / off-peak hours, Tempo or EJP (EDF regulated “tarif bleu” prices of 1 August 2026), for what you consume; the buy-back rate for surplus set by the order in force, for what you export.
- How it is calculated
- Saving = self-consumed energy valued at the price of each hour + exported energy × buy-back rate. With Tempo and EJP, each hour is valued at its own price over a typical year of blue, white and red days (normal and peak days for EJP). The rates set by the order are read from a table updated with each order. Without surplus sale and with a kit, the surplus is not valued. With total sale, the whole production is sold at the total-sale rate. With a virtual battery, the surplus is no longer paid at the buy-back rate (see NC.16). There is no longer any self-consumption bonus.
- What you can do
- You can choose your tariff option (Base, peak / off-peak hours, Tempo, EJP) and enter your price per kWh.
- Limit
- Electricity prices change, and the rates set by the order change about four times a year. With Tempo and EJP, the expensive days are those of a typical year: the actual calendar is only announced the day before by RTE.
Projection and payback
- Where it comes from
- Year-by-year projection: module degradation, electricity +3% per year (assumption), surplus buy-back +2% per year (indexation set by the order).
- How it is calculated
- The TURPE grid access charge (26.40 € per year) is deducted every year: net profit, NPV and IRR are therefore net of this cost. Payback is the year when the cumulative balance turns positive.
- What you can do
- Electricity price inflation can be set from 0 to 8% per year in the interactive console. The setting is frozen in your baseline study.
- Limit
- The rise in electricity prices is an assumption: nobody knows the price in 2040.
How the capacity is chosen
- Where it comes from
- The optimiser tests every possible roof capacity with the same hourly profile.
- How it is calculated
- Financial return: the shortest payback. Self-sufficiency: the highest self-production rate, as long as the configuration remains reasonably profitable. Balance: a weighted compromise. Sell (total sale): the highest net profit over 20 years, with a capacity of at least 9 kWp. If no capacity is profitable, the simulator will tell you.
- What you can do
- Changing priority relaunches the choice. You can also impose your own capacity at the next step.
- Limit
- Payback depends on the estimated cost: an actual quote can shift the best capacity.
Capacity and number of panels
- Where it comes from
- The capacity grid is a multiple of the capacity of one panel, starting at 1 kWp.
- How it is calculated
- The slider goes up to the measured capacity of the roof plus 20%, within a limit of 36 kWp. A plug & play kit stops at 3 kWp, while total sale starts at 9 kWp.
- What you can do
- You can change the panel capacity in Wp: the grid is recalculated, unless you have chosen a specific model.
- Limit
- The mark on the ruler shows the measured capacity of the roof. Beyond it, the panel layout no longer places all the panels and flags it.
Installation cost
- Where it comes from
- A price scale drawn up with a professional installer and corroborated by market ranges in France for 2025-2026: 2,200 € excl. VAT of fixed costs, plus a price per Wp that falls in bands.
- How it is calculated
- Cost always taken here as including VAT: VAT at 5.5% for panels up to 9 kWp, 20% above that, and the battery stays at 20% on its own line. Estimated cost = fixed cost + sliding price per Wp. The cost is never stored: it is recalculated for each capacity tested.
- What you can do
- Enter your quote: it fully replaces the estimate.
- Limit
- It is a market estimate. An actual quote always takes precedence.
Panels and inverter
- Where it comes from
- The datasheet of the chosen model when it exists, otherwise generic values: performance ratio of 0.85 (string), 0.84 (micro) or 0.86 (optimisers).
- How it is calculated
- The type of equipment also sets the packing density and the tolerance to shading. Modules lose 0.5% of output per year by default.
- What you can do
- In expert mode, choose the manufacturer and the model from the catalogue. For the 5.5% VAT rate, the list of certified modules is checked for you.
- Limit
- A model missing from the list stays “to be checked”, never refused.
Home battery
- Where it comes from
- Five standard capacities (5 to 15 kWh) and a custom capacity of your choice (1 to 30 kWh), each calculated hour by hour over the 8,760 hours, not with an estimation formula.
- How it is calculated
- Efficiency of 95% on charging and 95% on discharging (about 90% round trip), maximum discharge of 90%, capacity loss of 2% per year, with replacement counted at full cost.
- What you can do
- Choose one of the five capacities or enter your own (1 to 30 kWh), and give the price of your model if you know it.
- Limit
- Combined with scheduling or the energy manager, the battery works on the surplus they leave: the simulator calculates the real combination, instead of adding up the gain of each lever taken separately.
Scheduling and energy manager
- Where it comes from
- Your declared appliances (water heater, washing machine, vehicle, pool) and their schedules.
- How it is calculated
- Each appliance keeps the same energy per day: only the hour changes. Scheduling moves some appliances' use into the daytime (for example, you schedule your machine to run at midday). The energy manager directly sends the surplus, hour by hour, in order of priority, to certain appliances.
- What you can do
- Turn each lever on or off and the calculation is redone with it.
- Limit
- The gains per appliance share the same production: the total never exceeds the overall gain shown.
Virtual battery
- Where it comes from
- The typical fee structure of operators: activation, subscription per kWp, return fees.
- How it is calculated
- The surplus is no longer sold at the buy-back rate: it is credited to your account with the operator, then returned when you need it. It is therefore valued at the retail price you avoid paying, minus the return fees (within the limit of what you still buy from the grid, hour by hour), then the subscription is deducted. It requires an installation that exports its surplus to the grid.
- What you can do
- Compare the operators over 5 to 25 years.
- Limit
- Operators' offers change: check them before committing. If a new offer or a change needs to be made in the simulator, please let us know.