3 kWp solar system: what it produces and earns in France
The most common size on a French house, worked out for three cities and four levels of usage, and what sets it apart from larger systems.
A 3 kWp system usually has six to eight modules depending on their individual power, a common size for French houses. Facing due south at 30°, it produces 3,227 kWh a year in Lille, 3,395 in Paris and 4,669 in Marseille, according to the European Commission’s PVGIS solar data. Its installed price is around €6,000, an estimate drawn from recent quotes rather than an official price. For a household using 4,500 kWh a year without electric heating, it covers 36 % of usage in Paris, self-consumes 47 % of its output and pays back in 18.0 years; in Marseille, in 14.9 years. It keeps two advantages specific to its size: income from selling surplus is free of income tax up to 3 kWp, and its output stays close to an average house’s usage, which limits the surplus sold at 1.1 c€/kWh.
How many years until your panels pay for themselves?
Pays for itself in
18.0 years
| Output per year | 3,395 kWh |
| Gain in year 1 | €329 |
| Installed price (estimate) | €6,000 |
| Net over 20 years | +€665 |
Département median, roof at 30° due south, surplus sold at 1.1 c€/kWh.
Checked by Radif Partners · Editorial policy · Method and sources
Years to pay back, city by city
The same roof does not give the same result everywhere: output differs by about 45 % between Lille and Marseille. But household usage matters more than the city, as the grid below shows.
| Household usage | Lille | Paris | Marseille |
|---|---|---|---|
| 2,500 kWh | over 20 years | over 20 years | over 20 years |
| 4,500 kWh | 18.8 years | 18.0 years | 14.9 years |
| 8,000 kWh | 13.3 years | 12.6 years | 9.8 years |
| 12,000 kWh | 10.9 years | 10.3 years | 7.6 years |
At 2,500 kWh a year, a 3 kWp system produces more than the household uses: most of it goes to the grid at 1.1 c€, and payback exceeds twenty years in all three cities. A smaller kit suits those households better. From 8,000 kWh, the same 3 kWp becomes very worthwhile, because almost everything it produces replaces bought electricity.
What a 3 kWp system does over the year
For the 4,500 kWh Paris household, the system produces 3,395 kWh, of which 1,605 are used on site and 1,790 exported. The bill saving reaches €321 in year one and surplus sales €20, less €12 of standing-charge surcharge: the net gain is €329. In Paris, June output is about three times December’s, which is why some is always exported in June.
How much of your output will you use yourself?
Self-consumption rate
46 %
| Used on site | 1,620 kWh |
| Exported to the grid | 1,909 kWh |
| Share of the bill covered | 36 % |
| Saving in year 1 | €324 |
Median French output (1,185 kWh/kWp), roof at 30° due south, hour-by-hour calculation.
3 kWp or bigger?
Going to 6 kWp doubles output but not savings, since daytime usage does not change. For a household using less than roughly 8,000 kWh, 3 kWp keeps the best 20-year result; above that, the 6 kWp page shows when the next size takes the lead. The calculator compares every size from 1 to 9 kWp for your commune.
Before you sign
Compare the installed price across several quotes, check the offer meets the conditions for reduced VAT and have the prior declaration filed before fitting. The date of the connection request fixes your feed-in tariff for twenty years.