Solar panel orientation and tilt: the guide with figures
“You need due south, otherwise it isn't worth it.” Wrong. Using PVGIS satellite data, we measured what each orientation and each tilt produces, and the result is more forgiving than people say.
- →Due south remains optimal, but within the South ± 45° arc (south-east to south-west) you lose only ~5%.
- →East or West: around −19%, which is real but far from disqualifying, and often offset by better self-consumption.
- →North: avoid (−43% at 30°). Only acceptable at a very shallow tilt.
- →Tilt: the 15-45° range stays within 5% of the optimum. Flat roof −15%, vertical facade −30%.
- →The real generation killer is not a few degrees of difference, it is shading.
Two settings, one generation figure
A solar panel has two geometric parameters: its orientation (the azimuth: which compass point it faces) and its tilt (the angle from the horizontal). Together, they determine how much solar radiation the surface captures over the year.
To give concrete, comparable figures, we simulated a typical 3 kWp system in Lyon (central France) with the European Commission's PVGIS engine, varying the orientation and the tilt. The values that follow are real annual generation figures, not rough guesses.
Orientation: aim for south, but not at all costs
This is the point on which the most preconceptions circulate. Here is the generation by orientation, with the tilt fixed at 30°:
The lesson: turning down a project because the roof faces south-east or south-west is a mistake, as the loss is marginal. East and West remain worthwhile, especially if you consume in the morning and evening. Only north is genuinely penalising.
Tilt: a comfortable range, not a single point
In France, the optimum tilt facing due south is around 30 to 35° (maximum generation ~3,710 kWh/year in our example). But the optimum is a plateau, not a peak: between 15 and 45°, you stay within 5% of the maximum. Most French roofs (25-45° pitch) fall right inside that range.
The two extremes cost more: a flat roof (0°) produces ~3,140 kWh (−15% vs the optimum, and it cannot be cleaned by rain), while a vertical installation (90°), such as a facade or balcony railing, drops to ~2,570 kWh (−30%).
The full orientation × tilt matrix
The table crosses the two parameters. Annual generation of a 3 kWp system in Lyon (kWh/year, PVGIS data). Green marks the best cell, red the configurations to avoid.
| Tilt | South | SE / SW | East / West | North |
|---|---|---|---|---|
| 0° (flat) | 3,140 | 3,140 | 3,140 | 3,140 |
| 15° | 3,500 | 3,380 | 3,090 | 2,620 |
| 30° | 3,680 | 3,490 | 2,970 | 2,080 |
| 45° | 3,680 | 3,440 | 2,800 | 1,570 |
| 60° | 3,500 | 3,230 | 2,530 | 1,110 |
| 90° (vertical) | 2,570 | 2,400 | 1,800 | 590 |
Absolute optimum: South at ~35° = ~3,710 kWh/year. The East/West and SE/SW values are averages of the two sides.
At a glance, the “green zone” is wide: everything from South to South-West/South-East, between 15 and 45°, is excellent. The red is concentrated on steeply tilted north and on East/West facades.
Three common roof cases
The East-West roof (two roof faces)
Very common. Each roof face loses ~19% compared with South, but you equip two roof faces: the available area doubles, and above all generation is spread out, with a morning peak in the East and an evening peak in the West. The result is a “wider” curve that matches a household's consumption (morning/evening) better and often improves the self-consumption rate.
The flat roof (garage, extension, apartment block)
Laid flat, all orientations are equivalent (~3,140 kWh). So panels are installed on ballasted trays tilted at 10-15°, facing south, to recover generation and benefit from self-cleaning by rain.
The facade or railing (vertical)
Reserved for cases with no roof available (flat, balcony kit). You lose ~30%, but the installation remains worthwhile on a small scale because the investment is low.
And what about shading?
Here is the real underlying message: debating 5 or 10° of orientation only makes sense if your roof is unobstructed. A single tree, a chimney or the neighbour's gable can cost more generation than a poor azimuth, and in a far less predictable way, because the shadow moves through the day and the seasons.
This is also where the choice of inverter matters: on a partly shaded roof, microinverters or optimisers limit the damage by isolating the affected panels. Before focusing on the last degree of tilt, take an honest inventory of the obstructions around your roof.
Key takeaways
- Do not give up on a project because of a south-east or south-west orientation: −5% is negligible.
- East/West remains worthwhile (−19%) and is often better for self-consumption.
- Avoid steeply tilted north; a flat roof is made up for with tilted trays.
- Any tilt between 15 and 45° is excellent, so there is no need to hunt for the perfect degree.
- Hunt down shading above all: it is what really decides.
The only way to get your figure (your roof, your orientation, your shading, your consumption) is to simulate it. Our free simulator does it hour by hour on the PVGIS data for your address.
Frequently asked questions
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