Roof geometry
Which roof pitch and orientation are worthwhile for solar PV?
Solar PV does not need a perfect south-facing roof. Many east-west and shallow-pitched systems achieve good yields, just at different times of day and with a different annual profile.
Short answer: in Germany, a south-facing roof with a pitch of about 25-40° is often favourable for the annual yield. That is not a universal optimum. East-west spreads generation across the day; a north-facing roof can also make sense, especially at a shallow pitch and with low additional installation costs. More yield does not automatically mean a higher return.
How much yield does a different roof orientation cost?
The following comparison keeps location, weather data and total capacity constant. This makes the effect of pitch and direction visible. It is an example for Berlin, not a blanket figure for Germany. For your roof, change the location and the actual inputs in the calculator.
| Roof | kWh/year | Share of South 35° | Compare |
|---|---|---|---|
| South 10° | 9,028 | 92% | Open in calculator: South 10° |
| South 35° | 9,853 | 100% | Open in calculator: South 35° |
| South 60° | 9,332 | 95% | Open in calculator: South 60° |
| North 10° | 7,481 | 76% | Open in calculator: North 10° |
| North 35° | 5,252 | 53% | Open in calculator: North 35° |
| North 60° | 3,561 | 36% | Open in calculator: North 60° |
| East + West 35° | 7,788 | 79% | Open in calculator: East + West 35° |
Monthly yield: south, north and east-west at 35°
| Month | South 35° | North 35° | East + West 35° |
|---|---|---|---|
| Jan | 264 | 108 | 160 |
| Feb | 526 | 104 | 286 |
| Mar | 759 | 346 | 589 |
| Apr | 1,154 | 499 | 891 |
| May | 1,136 | 969 | 1,100 |
| Jun | 1,278 | 1,052 | 1,209 |
| Jul | 1,286 | 896 | 1,146 |
| Aug | 1,214 | 622 | 982 |
| Sep | 967 | 298 | 699 |
| Oct | 646 | 213 | 424 |
| Nov | 397 | 68 | 181 |
| Dec | 225 | 77 | 121 |
Data as of 2026-09-28. Berlin (52.52° N, 13.405° E), PVGIS 5.3 / SARAH3 (EU JRC), typical meteorological year; monthly irradiance scaled with DWD DUETT (1991-2020) (© Deutscher Wetterdienst, Germany's national weather service, CC BY 4.0; processed by us). Calculated with our solar model, not with PVGIS PVcalc: 14% configured system loss, additional model-internal temperature and reflection losses, no additional local shading, no inverter limit. East-west: 5 + 5 kWp; otherwise only one roof side with 10 kWp. Rounded values; not a weather forecast. The live calculator loads current weather data, so later results may differ.
You should assess a north side separately: Are solar panels on a north-facing roof worthwhile?
What does azimuth mean in the calculator?
Our calculator uses the compass convention: 0° = north, 90° = east, 180° = south, 270° = west. The roof pitch is measured from the horizontal: 0° is flat.
The PVGIS PVcalc interface, by contrast, uses a south-based azimuth (0° south, −90° east, +90° west). Do not transfer such angles unchanged into our calculator. The comparison links above already use our compass values.
Which roof pitch is favourable?
In Germany, a high annual yield for a south-facing orientation is often found in the range of about 25° to 40°. That is not a universal optimum: latitude, local weather and the desired generation profile shift the best angle.
- Shallower pitch: tends to favour the summer and reacts less strongly to the compass direction.
- Steeper pitch: can make better use of the low winter sun, but does not necessarily deliver the maximum in summer.
- Very flat modules: need adequate drainage and can get dirtier.
South or east-west?
A south-facing surface concentrates production more around midday and, at a favourable pitch, usually maximises the annual yield per kWp. East-west spreads production: east modules start earlier in the morning, west modules deliver for longer in the afternoon.
For households, the broader curve can be valuable because it coincides better with breakfast, working from home or consumption in the late afternoon. Whether that is economically better depends on consumption, feed-in tariff, inverter sizing and battery storage, not only on the annual yield.
No overall winner: maximum kWh per kWp and maximum self-consumption are different goals. In the simulator, compare both the annual figure and the daily curve.
Flat roofs and multiple roof sides
On flat roofs, the mounting angle can be chosen freely. Low east-west mounting often allows dense coverage and reduces mutual shading, while south-facing rows need larger spacing. The simulator compares the energy geometry but does not replace layout or wind load planning.
On a gable roof, both sides can be modelled separately. Split the installed kWp according to the number of modules and set each side's own azimuth.
How to measure your roof
- Determine the compass direction from a map view or building documents.
- Take the pitch from the roof plan, a digital inclinometer or a professional measurement.
- Note dormers, chimneys, trees and neighbouring buildings as possible sources of shade.
- Compare several variants in the Solar Simulator.