How many kWp for solar panels in Luxembourg? The complete sizing method
Sizing is the most critical step in a photovoltaic project in Luxembourg: an installation that is too small lacks profitability, while one that is too large exceeds the Klimabonus cap of €10,000 (reached at 15 kWp) and generates undervalued surplus. The right formula for a Luxembourg single-family home: annual consumption (kWh) ÷ 850 kWh/kWp. In practice, the vast majority of homes fall between 4 and 12 kWp, with 5–6 kWp being the most common configuration for a household without heavy equipment.
kWp explained: peak power vs. real output
The kilowatt-peak (kWp) measures the maximum theoretical power of a photovoltaic installation under standardised laboratory conditions: 1,000 W/m² irradiance, cell temperature 25°C, AM 1.5 spectrum. This is the value on panel data sheets and the basis for sizing calculations and Klimabonus rates.
In reality, peak power is never sustainably achieved in the field. A standard 2026 monocrystalline solar panel has a unit power of 400–450 Wp and occupies approximately 1.75 m². A 5 kWp installation will therefore typically comprise 11–13 panels.
1 kWp installed under optimal conditions (due south orientation, 30–35° tilt) produces approximately 850 kWh per year in Luxembourg. This already incorporates real losses: inverter (~5%), cabling (~2%), summer temperatures, light dust and overcast days. For south-east or south-west orientation, expect 800 kWh/kWp/year. This reference value is confirmed by the Klima-Agence Luxembourg.
Peak power (kWp)
- Theoretical value under laboratory conditions
- Used for installation sizing
- Basis for Klimabonus grant calculations
- Determines number of panels and required area
Real output (kWh/year)
- Energy actually produced on site
- Depends on orientation, tilt and shading
- Basis for savings and ROI calculation
- ~850 kWh/kWp/year in Luxembourg under optimal conditions
Calculate your ideal power and estimate your Klimabonus 2026 grants in 2 minutes.
Simulate my installation →Solar irradiation in Luxembourg: 850 kWh/kWp/year — what this means in practice
Luxembourg benefits from a global solar irradiation of approximately 1,000–1,100 kWh/m²/year on a horizontal surface, and 1,100–1,200 kWh/m²/year on an optimally tilted surface. Irradiation is homogeneous across the Grand Duchy territory, with variations below 5% between regions.
| Installed power | Estimated annual output | Household consumption equivalent |
|---|---|---|
| 3 kWp | ~2,550 kWh/year | Small flat, 1–2 people (no electric heating) |
| 5 kWp | ~4,250 kWh/year | Family of 3–4, standard configuration |
| 8 kWp | ~6,800 kWh/year | Large house or household with air/water heat pump |
| 10 kWp | ~8,500 kWh/year | Large house with heat pump + electric vehicle |
Output calculated on the basis of 850 kWh/kWp/year (optimal conditions, due south orientation, 30–35° tilt). Source: Klima-Agence Luxembourg.
Solar output in Luxembourg varies greatly by season. In June–July, a 5 kWp system can produce 600–700 kWh per month. In December–January, the same system produces only 150–200 kWh. Never size « for winter »: an installation calibrated on winter consumption would be massively oversized in summer and generate poorly-valued injection.
The sizing formula step by step
Example: 4,500 kWh ÷ 850 = 5.3 kWp → rounded to 5.5 or 6 kWp depending on module availability.
Determine your actual annual consumption (kWh/year)
Check your last 2–3 Creos or Sudstroum bills. Include projected consumption from planned future equipment (heat pump, EV) within the next 3–5 years — expanding an installation later is very costly.
Calculate the gross required power
Power (kWp) = Annual consumption (kWh) ÷ 850 kWh/kWp. This formula assumes a due-south installation at 30–35° — the reference case for Luxembourg.
Apply the orientation correction factor
If your roof is not due south, divide by the corresponding correction coefficient (see section 6). Example: south-east at 30° → coefficient 0.92, so 5.3 ÷ 0.92 = 5.75 kWp → rounded to 6 kWp.
Check constraints and caps
Verify: (a) available roof area, (b) 30 kWp residential cap for Klimabonus eligibility, (c) 15 kWp threshold above which the grant is capped at €10,000 with no further progression.
In Luxembourg in 2026, the Klimabonus scheme requires operating in self-consumption mode for maximum grants. Sizing for 80% of annual needs while maximising the self-consumption rate is generally more profitable than sizing for 100% coverage with a low self-consumption rate.
Consumption by Luxembourg household profile
| Household profile | Typical consumption (kWh/year) | Notes |
|---|---|---|
| Studio/flat, 1 person, non-electric heating | 1,500–2,500 kWh | Standard appliances only |
| 2–3 room flat, 2 people, non-electric heating | 2,500–3,500 kWh | Washer, dryer, TV, fridge |
| 4–6 room house, 3–4 people, non-electric heating | 3,500–5,500 kWh | Most common profile in Luxembourg |
| House with air/water heat pump | 6,000–10,000 kWh | Electric heating adds 2,000–5,000 kWh/year |
| House with heat pump + EV | 8,000–14,000 kWh | EV adds 1,500–3,000 kWh/year |
| Passive/low-energy house, 4 people | 2,500–4,000 kWh | Very good insulation = reduced consumption |
Your precise annual consumption is on your annual Creos statement (or Sudstroum for southern municipalities). You can also consult it online via MyCreos (my.creos-net.lu) with quarter-hour granularity if you have a smart meter.
Quick sizing table by profile
| Profile / Consumption | Recommended power | Panels (~420 Wp) | Annual output | Indicative Klimabonus |
|---|---|---|---|---|
| Small flat / 2,000–2,500 kWh | 2.5–3 kWp | 6–8 | 2,125–2,550 kWh | ~€2,500–3,750 |
| Standard house / 4,000–5,000 kWh | 5–6 kWp | 12–14 | 4,250–5,100 kWh | ~€6,250–7,500 |
| House + heat pump / 7,000–9,000 kWh | 8–10 kWp | 19–24 | 6,800–8,500 kWh | ~€8,750–10,000 |
| House + heat pump + EV / 9,000–12,000 kWh | 10–12 kWp | 24–29 | 8,500–10,200 kWh | ~€10,000 (max) |
Indicative Klimabonus based on the formula in force since 4 January 2026. The €10,000 cap is reached at 15 kWp. Verify exact amounts at aides.klima-agence.lu.
Impact of orientation and tilt on solar output
The optimal orientation in Luxembourg is due south (azimuth 180°), with a tilt between 30° and 35°. A non-optimal orientation simply requires slightly increasing installed power to compensate.
| Orientation | Tilt | Production factor | Estimated output/kWp | Loss vs. optimum |
|---|---|---|---|---|
| Due South | 30–35° | 1.00 (reference) | ~850 kWh | 0% |
| South-East / South-West | 30° | 0.92–0.95 | ~780–810 kWh | 5–8% |
| East / West | 30° | 0.75–0.80 | ~640–680 kWh | 20–25% |
| Due South — flat roof (10°) | 10° | 0.90–0.92 | ~765–780 kWh | 8–10% |
| North (not recommended) | 30° | 0.55–0.65 | ~470–550 kWh | 35–45% |
For homes with a pitched roof oriented east-west (north-south ridge), installing panels on both slopes provides a more spread-out daily production profile — with morning and evening output — which significantly improves self-consumption rate.
Impact of heavy equipment on optimal sizing
Certain equipment significantly changes optimal PV sizing and must be accounted for from the design phase, especially if planned within the next 5 years.
Air/water heat pump (+2,000–5,000 kWh/year)
A well-sized heat pump for a 150m² home typically consumes 3,000–4,000 kWh/year for heating and domestic hot water. For a 200m² home, expect 4,000–6,000 kWh/year. This justifies increasing PV power by 3–6 kWp vs. a non-heat-pump household. Strategic advantage: the heat pump can be controlled to operate preferentially during solar production hours, improving self-consumption rate.
Electric vehicle (+1,500–3,000 kWh/year)
For 15,000 km/year with a car consuming 17–20 kWh/100 km, expect 2,550–3,000 kWh of annual home charging. To maximise direct solar self-consumption, programme charging during production hours via a solar-controlled EVSE.
Heated pool (+1,500–3,000 kWh/year)
A heated outdoor pool (filtration pump + resistance or pool heat pump) consumes 1,500–3,000 kWh per season. Major advantage: pool consumption coincides perfectly with solar production (spring-summer), making it an ideal consumer to absorb summer surplus.
Even for a household with heat pump + EV, the optimal power rarely exceeds 12–14 kWp in Luxembourg. Beyond 15 kWp, you reach the grant cap (€10,000) but continue investing without additional subsidy. In practice, a 10–12 kWp installation with an 8–10 kWh battery is the best balance for heavy consumers in 2026.
Sizing and Klimabonus 2026 caps: optimising your grant
| Rule | Value / Condition | Sizing implication |
|---|---|---|
| Minimum eligible power | 2 kWp | Below this: no grant. Installations ≥ 2 kWp only. |
| Maximum panel grant | €10,000 (reached at 15 kWp) | Beyond 15 kWp: no additional grant on panels. |
| Maximum residential power | 30 kWp | Above this → industrial category, different rules. |
| Required mode | Self-consumption | Waiver of guaranteed feed-in tariff required for new scheme. |
| Pre-financing available | Since 4 January 2026 | Grant deducted directly from invoice — no upfront cash needed. |
| Battery maximum grant | €2,250 (reached at 9 kWh) | Battery subsidisable between 2 and 9 kWh usable capacity. |
For the new Klimabonus, the installer must submit the grant application before any work begins. No grant can be awarded retrospectively. The guaranteed injection tariff is incompatible with the new Klimabonus — by choosing pre-financing, you permanently waive the guaranteed tariff.
Precisely calculate your 2026 Klimabonus grant and receive quotes from certified installers.
Request free quotes →Roof area needed by installed power
| Installed power | Panels (~420 Wp) | Net panel area | Required roof area |
|---|---|---|---|
| 3 kWp | 8 | ~14 m² | ~18–20 m² |
| 5 kWp | 12 | ~21 m² | ~26–30 m² |
| 8 kWp | 19–20 | ~33–35 m² | ~40–45 m² |
| 10 kWp | 24 | ~42 m² | ~50–55 m² |
| 15 kWp | 36 | ~63 m² | ~75–80 m² |
The Luxembourg government provides an official free solar cadastre on the Luxembourg Geoportal (map.geoportail.lu). Complement with the Klima-Agence grant simulator at aides.klima-agence.lu.
5 common sizing mistakes in Luxembourg — and how to avoid them
Sizing without knowing actual consumption
Estimating consumption from memory leads to 20–30% undersizing. Solution: check your last 2 annual Creos/Sudstroum bills before speaking to any installer.
Forgetting future equipment
Not integrating a planned heat pump or EV (within 3 years). Expanding an installation later costs a great deal. Solution: include all equipment planned in the next 5 years in your base consumption from the start.
Maximising size without considering Klimabonus caps
The grant is capped at €10,000 reached at 15 kWp. Beyond that, each additional kWp is 100% self-funded. Solution: unless you have documented needs above 12,000 kWh/year, stay below 15 kWp.
Failing to correct for roof orientation
Installing 5 kWp on an east-west roof without applying the correction factor produces 20–25% less than expected. Solution: apply the orientation correction factor systematically.
Confusing oversizing with profitability
With consumption of 3,500 kWh/year and a 10 kWp installation, 60–70% of production is injected at market rate (lower than avoided purchase price). Solution: right sizing maximises self-consumption — ideally 40–50% for a battery-free installation.
Official tools and simulators for sizing in Luxembourg
Klima-Agence Simulator — aides.klima-agence.lu
The official Klima-Agence tool estimates all available grants: Klimabonus, municipal grants, Enoprimes and nova naturstroum fund. Updated with 2026 rates. Essential starting point for any PV project in Luxembourg.
Luxembourg Geoportal — Solar Cadastre — map.geoportail.lu
Enter your address to visualise solar potential of each roof section in 3D, estimating usable area, solar radiation received and potential annual production, accounting for obstacles and actual roof geometry.
Renov.lu Simulator — renov.lu/panneaux-solaires/simulateur/
Our Luxembourg-market simulator integrates the latest cost data and Klimabonus 2026 rates to give personalised production, profitability and self-consumption estimates in minutes.
Free independent Klima-Agence advice — (+352) 8002 11 90
Free, independent advisory service for all Luxembourg households. Available by phone (freephone) or home visit. Completely independent of any installer — valuable to validate your sizing before signing.
Frequently asked questions about PV sizing in Luxembourg
What is the minimum power for Klimabonus in Luxembourg in 2026?
The minimum power required to be eligible for the 2026 Klimabonus is 2 kWp according to the official government announcement of 9 January 2026. Note: under the previous scheme (orders between 1 January 2022 and 4 March 2026), the minimum was 4 kWp for single-family homes.
How many kWp for a 150 m² house in Luxembourg?
House area is not the right criterion — actual annual consumption is what matters. For a standard 150m² house (3–4 people, gas/oil heating): typically 4,000–5,500 kWh/year → 5–6.5 kWp. With a heat pump: 7,000–10,000 kWh/year → 8–12 kWp.
Is self-consumption or injection better in Luxembourg in 2026?
In 2026, self-consumption is clearly the most advantageous strategy for new installations. Grid electricity purchase price (~€0.21–0.28/kWh) is well above the guaranteed feed-in tariff (€0.1374/kWh). Each self-consumed kWh is worth approximately 2–4 times more than an injected kWh. The new 2026 Klimabonus scheme also offers maximum grants only in self-consumption mode.
How does Klimabonus pre-financing work?
Since 4 January 2026, Klimabonus pre-financing allows households to pay only the net installation cost (total cost minus State grant), deducted directly from the installer’s invoice. Mandatory condition: the installer must be registered on the official pre-financing register at guichet.public.lu.
How many panels for 5 kWp in Luxembourg in 2026?
With standard 2026 monocrystalline modules (400–450 Wp unit power), a 5 kWp installation requires 11–13 panels. Required roof area is approximately 20–22 m² net panel area, or 25–30 m² of roof including safety margins.
Take action — simulate your installation and request quotes
You now know the sizing rules in Luxembourg. Next step: simulate your installation to find out exactly your 2026 Klimabonus grants, then request and compare free quotes from certified installers registered on the official pre-financing register.