How many kWp of solar panels should you install in Luxembourg for your consumption?
By Yacine Sahnoune, founder of renov.lu
In Luxembourg, 1 kWp of well-oriented panels produces about 1,000 kWh a year (1,067 kWh due south according to PVGIS). The right output covers 80 to 100% of your annual consumption: 3.5 to 5 kWp for 4,000 to 5,000 kWh, 8 to 9 kWp with a heat pump. Allow 5.5 to 6 m² of roof per kWp.
- Production: 1,000 kWh per kWp per year assumed; PVGIS gives 1,067 kWh in Luxembourg City due south, 1,034 in Clervaux, 1,086 in Esch-sur-Alzette
- Formula: output (kWp) ≈ annual consumption (kWh) ÷ production per kWp of your roof
- Orientation: south-east or south-west −6%, east or west −19%, flat roof at 10° −8%, north −46%
- Typical household: 3,900 kWh a year, i.e. about 4 kWp
- Area: a 440 Wp module measures about 2 m²; 6 kWp = 14 modules and 32 to 36 m² of roof
- Seasons: July brings 12% of annual production, December 3%
- Grant: 2 kWp minimum; the Klimabonus stops rising above 15 kWp
The right output for your roof, calculated
Address, orientation, consumption: the simulator suggests an output, a production figure and the matching grant.
How many kWh does 1 kWp of solar panels produce in Luxembourg?
One kWp (kilowatt-peak, the module output under laboratory conditions) produces 1,067 kWh a year in Luxembourg facing due south at a 35° tilt, according to the European Commission’s PVGIS tool, system losses included. For sizing, use 1,000 kWh: the margin covers light shading and module ageing. The gap between the north and south of the country is small.
| Location (due south, 35°) | Production per kWp per year (PVGIS) |
|---|---|
| Clervaux (north) | 1,034 kWh |
| Luxembourg City | 1,067 kWh |
| Esch-sur-Alzette (south) | 1,086 kWh |
Production is highly seasonal: for 1 kWp facing south, PVGIS counts about 130 kWh in June and July, but 32 to 37 kWh in November, December and January. A 6 kWp system therefore produces nearly 800 kWh in July and less than 200 kWh in December: sizing to cover the winter would create a huge summer surplus.
The four-step sizing method
- Find your annual consumption on your supplier’s statement or your grid operator’s customer portal. Failing that, the government’s reference household uses 3,900 kWh a year.
- Add the uses planned within five years. Heat pump: heat demand divided by its seasonal efficiency, for example 15,000 kWh of heat ÷ 3.5 ≈ 4,300 kWh of electricity. Electric car: 15,000 km × 17 kWh per 100 km ≈ 2,550 kWh.
- Divide by the production of 1 kWp on your roof: 1,000 kWh due south, about 940 kWh south-east or south-west, 810 kWh east or west.
- Aim for 80 to 100% of the result, then round to the number of modules the roof can take.
A family uses 4,500 kWh a year and buys an electric car (2,550 kWh): 7,050 kWh in total. Its roof faces east-west (810 kWh per kWp): 7,050 ÷ 810 = 8.7 kWp. At 80-100%, it aims for 7 to 9 kWp, i.e. 16 to 20 modules of 440 Wp spread over both slopes, for a Klimabonus of €6,468 to €7,722.
Recommended output by consumption profile
For a roof facing due south, the recommended output can be read straight from this table; for an east-west roof, increase it by about a quarter.
| Profile | Annual consumption | Recommended output (south roof) | 440 Wp modules | Klimabonus 2026 |
|---|---|---|---|---|
| Couple, small house | 2,500 to 3,000 kWh | 2.5 to 3 kWp | 6 to 7 | €2,681 to €3,168 |
| Typical household | 3,900 kWh | 3 to 4 kWp | 7 to 9 | €3,168 to €4,092 |
| Family of four | 4,500 to 5,500 kWh | 4 to 5.5 kWp | 9 to 13 | €4,092 to €5,354 |
| Family + electric car | 7,000 to 8,000 kWh | 6 to 8 kWp | 14 to 18 | €5,742 to €7,128 |
| House with a heat pump | 8,500 to 9,500 kWh | 7 to 9 kWp | 16 to 21 | €6,468 to €7,722 |
| Heat pump + electric car | 11,000 to 12,000 kWh | 9 to 12 kWp | 21 to 28 | €7,722 to €9,108 |
Matching prices are on our page on solar panel costs, grant conditions on the solar grants page. For a heat pump, its real consumption is detailed in our guide to heat pump electricity consumption.
Orientation and tilt: how much production do you lose?
Due south at a tilt of 30 to 45° is ideal in Luxembourg, but a south-east, south-west or east-west roof remains profitable; only the north slope should be ruled out. Coefficients calculated with PVGIS for Luxembourg City:
| Orientation and tilt | PVGIS production per kWp | Compared with the optimum | Value to use |
|---|---|---|---|
| South, 35° | 1,067 kWh | 100% | 1,000 kWh |
| South, 45° | 1,060 kWh | 99% | 990 kWh |
| South-east or south-west, 35° | 1,006 kWh | 94% | 940 kWh |
| South, 10° (flat roof) | 983 kWh | 92% | 920 kWh |
| East or west, 15° (east-west flat roof) | 903 kWh | 85% | 850 kWh |
| East or west, 35° | 868 kWh | 81% | 810 kWh |
| North, 35° | 580 kWh | 54% | avoid |
An east-west roof produces 19% less per kWp, but spreads production from morning to evening: you use a larger share of what you produce. Covering both slopes makes up the loss with a few extra modules. Flat or pitched roof: structural and cost constraints are explained in our guide to flat versus pitched roofs.
Roof area needed for each output
A common 430 to 450 Wp module measures about 1.7 × 1.1 m, nearly 2 m². Adding clearances to the verges, ridge and obstacles (chimney, roof window), allow 5.5 to 6 m² of roof per kWp.
| Output | 440 Wp modules | Module area | Roof needed |
|---|---|---|---|
| 3 kWp | 7 | ≈ 14 m² | 16 to 20 m² |
| 6 kWp | 14 | ≈ 27 m² | 32 to 36 m² |
| 9 kWp | 21 | ≈ 41 m² | 46 to 52 m² |
| 12 kWp | 28 | ≈ 55 m² | 60 to 66 m² |
| 15 kWp | 34 | ≈ 66 m² | 74 to 80 m² |
The solar cadastre on the national geoportal (map.geoportail.lu) shows the usable area and exposure of every roof slope in the country: a good starting point before the installer’s visit.
Why not cover the whole roof with panels?
Because beyond your consumption, each extra kWp earns little: its electricity is mostly sold at market price, about 4 cents per kWh, while the grant per kWp falls. Going from 6 to 9 kWp costs about €4,500 more for €1,980 of extra grant: each additional kWp costs €840 and earns around sixty euros a year, a payback of more than fourteen years.
- Exception: future uses. A heat pump or electric car planned within five years justifies sizing bigger right away: an extension is only funded if commissioned at least 2 years after the first injection.
- Exception: the feed-in tariff. For a large roof that exports a lot, the guaranteed tariff of €0.1333/kWh (up to 10 kWp) can make a bigger system worthwhile: the calculation is on our page on payback: Klimabonus or feed-in tariff.
- Above 15 kWp, the Klimabonus stays at €10,000: each extra kWp is entirely at your expense.
From calculation to quote
Once you have your target output, have it checked on site: the installer checks the usable area, shading and structure, then prices the system with the grant deducted.
Check your sizing
Simulate your roof, then receive three quotes from installers established in Luxembourg.
Frequently asked questions about solar sizing
How many kWh does 1 kWp of solar panels produce in Luxembourg?
According to PVGIS, 1 kWp facing due south at a 35° tilt produces 1,067 kWh a year in Luxembourg City, 1,034 kWh in Clervaux and 1,086 kWh in Esch-sur-Alzette. For sizing, use 1,000 kWh, or about 810 kWh for an east- or west-facing slope.
How many panels do you need for 5 kWp?
With common 440 Wp modules, 5 kWp needs 11 to 12 panels, about 23 m² of modules and 27 to 30 m² of roof. With 400 Wp modules, you need 13.
What output should I install for a consumption of 4,000 kWh a year?
About 3.5 to 4 kWp on a roof facing due south, i.e. 80 to 100% of consumption at 1,000 kWh per kWp. On an east-west roof, allow 4 to 5 kWp. If a heat pump or electric car is planned, add its consumption before calculating.
How much roof area is needed for 6 kWp?
You need 14 modules of 440 Wp, about 27 m² of modules and 32 to 36 m² of roof including clearances to the edges and obstacles. Allow 5.5 to 6 m² of roof per kWp.
Is an east-west facing roof worth it?
Yes. An east or west slope produces about 19% less than a south slope, but production is spread from morning to evening, which increases the share you use yourself. Fitting modules on both slopes makes up the loss.
Should I plan more kWp for an electric car or a heat pump?
Yes, if it is coming within five years. A car driving 15,000 km a year adds about 2,550 kWh, a heat pump several thousand kWh depending on the house. Including them from the start costs less than an extension, which is only funded 2 years after the first injection.
Can a solar system be extended later?
Yes, technically, but the extension only receives the Klimabonus if it is commissioned at least 2 years after the first injection of the existing system, and it often requires a more powerful inverter. It is better to size for the next five years’ needs from the outset.