Complete DIY solar kits for a French house: the numbers
A kit of a few panels costs a fraction of a fitted system. What it earns, what it cannot do, and the formalities that stay exactly the same.
A solar kit bundles panels, an inverter or micro-inverters, cables and sometimes the mounting, sold together for a homeowner to fit. Average prices found in early 2026 across several hundred kits range from €514 for 1 kWp to €1,094 for 3 kWp, excluding the mount: far less than the €6,000 estimated for 3 kWp fitted by a professional. In Paris, for a household using 4,500 kWh that consumes 47 % of a 3 kWp kit’s output, the saving reaches €321 a year, and the kit pays back in 3.4 yrs if there are no mounting or connection costs. A 1 kWp kit, almost entirely self-consumed, pays back in 2.5 yrs. These figures assume correct fitting with no shade and do not count your time. Planning formalities at the town hall and the declaration to Enedis, the grid operator, are the same as for a fitted system.
How many years until your panels pay for themselves?
Pays for itself in
16.4 years
| Output per year | 2,263 kWh |
| Gain in year 1 | €282 |
| Installed price (estimate) | €4,650 |
| Net over 20 years | +€1,022 |
Département median, roof at 30° due south, surplus sold at 1.1 c€/kWh.
Checked by Radif Partners · Editorial policy · Method and sources
Kit or professional fitting: the numbers side by side
The table compares, for three sizes, a self-fitted kit with no surplus sales and a system fitted by a company with surplus sold at the feed-in tariff. Both produce the same on the same roof; only the price and the export income differ.
| Size | Option | Price (estimate) | Self-consumed | Year-1 gain | Pays back in |
|---|---|---|---|---|---|
| 1 kWc | DIY kit, no sales | €514 | 91 % | €206 | 2.5 yrs |
| 1 kWc | Professionally fitted, surplus sold | €3,350 | 91 % | €195 | 17.1 yrs |
| 2 kWc | DIY kit, no sales | €926 | 63 % | €284 | 3.3 yrs |
| 2 kWc | Professionally fitted, surplus sold | €4,650 | 63 % | €282 | 16.4 yrs |
| 3 kWc | DIY kit, no sales | €1,094 | 47 % | €321 | 3.4 yrs |
| 3 kWc | Professionally fitted, surplus sold | €6,000 | 47 % | €329 | 18.0 yrs |
At 3 kWp, the fitted system earns slightly more each year thanks to surplus sales (€20 in year one), but it costs several times the kit’s price. The payback gap comes from the price, not the output.
What a kit cannot do
- No installer guarantee on the fitting: roof watertightness and electrical connection are your responsibility.
- A size limited by what you can fix and connect safely.
- A surplus that, without a purchase contract, goes to the grid unpaid.
For a small kit plugged into a socket, see the plug-in panel page. To decide what size to aim for, the how many panels page works out the best-value size.
Which formalities for your system?
Planning
Prior declaration
| Enedis connection | Request + feed-in contract |
| Sale income taxable | No (3 kWp or less) |
The file goes to the town hall; it is processed within one month, two in protected areas.
A solar kit with a battery: the price not to exceed
Without a purchase contract, everything the kit produces in excess goes to the grid unpaid. A battery recovers part of that surplus for the evening: each stored kWh is then worth the full price of a purchased kWh, not the export tariff. That is why a battery makes more sense on a kit with no sales than on a system that sells its surplus. The table gives, for each kit, the price above which the battery does not pay for itself within twenty years.
| Kit | Battery | Self-consumed | Extra used per year | Extra saving per year | Break-even price |
|---|---|---|---|---|---|
| 1 kWc | 2.5 kWh | 91 % → 99 % | 92 kWh | €18 | €369 |
| 1 kWc | 5 kWh | 91 % → 99 % | 93 kWh | €19 | €372 |
| 2 kWc | 2.5 kWh | 63 % → 84 % | 486 kWh | €97 | €1,947 |
| 2 kWc | 5 kWh | 63 % → 94 % | 697 kWh | €139 | €2,789 |
| 3 kWc | 2.5 kWh | 47 % → 66 % | 635 kWh | €127 | €2,543 |
| 3 kWc | 5 kWh | 47 % → 78 % | 1,058 kWh | €212 | €4,234 |
Compare this break-even price with that of the battery you have in mind, inverter or charger included. The gain levels off quickly: once the battery can absorb a sunny day’s surplus, extra capacity adds almost nothing. The solar panels with battery page runs the same calculation for a fitted system.
The formalities do not change
Fitting it yourself exempts you from nothing. On a roof, the prior declaration of works is filed at the mairie before fitting; it is processed within one month, two in a protected area. Any system connected to your home wiring is then declared to Enedis: a self-consumption agreement without export if you sell nothing, a connection request if you want a purchase contract. The installation and paperwork page lists them in order.
Getting a kit’s price right
Add the mount, suitable electrical protection and, if you sell surplus, any connection fees to the kit price. Enter the total in the calculator: a kit that looks profitable at its catalogue price can be much less so once everything is counted. To compare with a complete system, the system cost page gives the 2026 benchmarks.