How Many Solar Panels Do I Need? — European Home Sizing Guide
The 4-step sizing formula
- Find your annual consumption in kWh. Check your electricity bill or utility portal — most EU utilities show annual kWh prominently. Typical ranges: 2,500 kWh (small apartment) to 6,000 kWh (large home with electric heating or EV).
- Decide your coverage target. 100% of annual consumption is the default goal, but without storage you can only self-consume 30–40% of generation. With battery: 60–85%. With heat pump + EV: up to 95% (you're consuming more at home).
- Divide by your country's yield factor. Each kWp of solar produces roughly 850–1,200 kWh/year in northern Europe and 1,400–1,700 kWh/year in southern Europe. A Dutch home needing 4,000 kWh needs 4,000 ÷ 900 = 4.4 kWp. A Spanish home needing the same kWh needs 4,000 ÷ 1,550 = 2.6 kWp.
- Convert kWp to panel count. Divide kWp by panel wattage (W) and multiply by 1,000. A 4.4 kWp system with 400W panels = 4,400 ÷ 400 = 11 panels. With 450W HJT panels = 10 panels.
Panel count by country and household size
Assumes 400W panels, 100% annual offset target, fixed-tilt south-facing roof, JRC PVGIS average yields, 0.80 performance ratio.
| Country | Peak sun (h/day) | Small home — 4,000 kWh/yr | Large home — 6,000 kWh/yr |
|---|---|---|---|
| Germany | 2.8 | 4.3 kWp (11 panels) | 6.4 kWp (16 panels) |
| Netherlands | 2.7 | 4.4 kWp (11 panels) | 6.7 kWp (17 panels) |
| Poland | 2.8 | 4.3 kWp (11 panels) | 6.4 kWp (16 panels) |
| France (central) | 3.3 | 3.7 kWp (10 panels) | 5.5 kWp (14 panels) |
| Austria | 3.1 | 4.0 kWp (10 panels) | 5.9 kWp (15 panels) |
| Italy (north) | 3.4 | 3.6 kWp (9 panels) | 5.3 kWp (14 panels) |
| Italy (south) | 4.3 | 2.8 kWp (7 panels) | 4.2 kWp (11 panels) |
| Spain | 4.5 | 2.7 kWp (7 panels) | 4.0 kWp (10 panels) |
| Portugal | 4.7 | 2.6 kWp (7 panels) | 3.9 kWp (10 panels) |
| Greece | 4.6 | 2.7 kWp (7 panels) | 4.0 kWp (10 panels) |
Will the panels fit on my roof?
A typical 400W panel is roughly 1.76 × 1.13 m ≈ 2 m². An 11-panel system therefore needs about 22 m² of usable roof area (allowing for inverter/wiring margin, about 25 m² total). Most European homes have 40–80 m² of south-facing or southeast/southwest roof area, so a 10–15 panel system almost always fits.
Rules of thumb:
- Each kWp ≈ 5 m² of roof
- East + west split counts as two separate arrays with 80–85% of south-facing yield each
- Flat roofs need ~1.5× the area (tilt racking spacing)
- Always leave 30–50 cm margin from roof edges per fire-code requirements in Germany/Austria
Factors that change the answer
- Adding an EV: add 1.5–2.5 kWp (4–6 panels) per 15,000 km/year of driving to cover charging.
- Adding a heat pump: add 2–4 kWp depending on home size and climate zone — heat pumps triple winter consumption.
- Adding a battery: doesn't change panel count, but shifts economics — you can justify a larger array because more generation becomes self-consumed rather than exported.
- Feed-in tariff caps: Germany caps payment on systems above 10 kWp (50% must be self-consumed). Size around this threshold if you're going bigger.
- Shading: if any part of the roof is shaded, use microinverters (Enphase) or DC optimisers (SolarEdge) — shaded panels no longer drag down unshaded ones.
Skip the manual math
Our system configurator asks for your country, monthly bill, and roof orientation and returns an exact panel count, recommended inverter, and 25-year savings — using the same JRC PVGIS data professional installers use. Takes under a minute.
Open configurator →Panel Sizing FAQs
How much roof area per kWp of solar?
Roughly 5 m² per kWp with modern 400–450W monocrystalline panels (2 m² per panel, 2.5 m² including wiring margin). Higher-efficiency HJT panels at 450W drop that to ~4.5 m²/kWp. Older polycrystalline needs 6–7 m²/kWp.
Should I oversize my solar system?
In southern Europe, yes — larger systems cover more of winter consumption and give you surplus to charge an EV or heat pump later. In Germany, stay at or under 10 kWp to avoid the EEG self-consumption requirement; above that, 50% must be self-consumed for full feed-in tariff. With a battery, a 20–25% oversize is optimal for most homes.
Do I need the same number of panels as my neighbour with the same house?
Not necessarily. Consumption varies 2–3× between households of similar size due to heating (gas vs heat pump), EV ownership, appliance efficiency, occupancy patterns, and home-office hours. Size from your actual kWh bill, not from a neighbour's install.
What size inverter should I pair with my panel count?
Inverter AC output is typically 80–100% of panel DC capacity. A 5 kWp system (12 × 400W panels) pairs well with a 4.2–5 kW inverter. Slight under-sizing (DC-to-AC ratio up to 1.25) is common practice — you sacrifice negligible peak generation and save money. Our configurator picks the right inverter automatically.
Do I need more panels to offset my electric heating?
If you run a heat pump, add 2–4 kWp on top of your base load. Critically: heat-pump consumption is concentrated in winter when solar generation is lowest (20–30% of summer), so solar only offsets roughly half of annual heat-pump energy use even with correct sizing. Battery helps modestly; gas-line time-shifting (charge battery on cheap hours) matters more.
Sources
- [1]JRC Photovoltaic Geographical Information System (PVGIS) — Country-level peak-sun-hour values used in panel-count estimates.
- [2]Eurostat — Electricity prices for household consumers — Baseline kWh rates across EU member states.
- [3]SolarPower Europe — Residential Solar Market Outlook — Residential solar adoption trends and typical system sizes.
- [4]Fraunhofer ISE — Electricity from Solar Photovoltaics — Reference performance-ratio data used in yield modelling.