Annual, summer and winter yield by angle
The tilt says how steep the module stands: 0 degrees lies flat, 90 degrees hangs vertically on the railing. For one location, the table shows what each angle yields facing south and with an east-west split, over the year, in summer and in winter.
Calculated with PVGIS 5.3 (PVcalc), radiation data PVGIS-SARAH3 2005–2023, PVGIS © European Union. Reference location Kassel, Germany (51.31° N, 9.48° E), 1 kWp crystalline modules, 14 % system losses, open horizon without shading, queried on October 16, 2026. The inverter's 800-watt limit is not included. East-west: average of modules facing east and facing west. “vs. best” refers to 40 degrees south, the highest value in the table; PVGIS gives 38 degrees as the optimal tilt for this location.
Vertical on the railing: 90 degrees
Most balcony systems hang vertically because that is the simplest mount. Facing south, that costs just under 30 percent over the year compared with the best tilt: 720 instead of 1017 kWh per kWp. Almost all of the loss happens in summer. From June to August, vertical yields 204 kWh per kWp, a 20-degree tilt 375. The high summer sun almost glances past a vertical surface.
Is a 30-degree angle worth it?
Facing south, yes, if your mount allows it: 30 degrees yields 1010 kWh per kWp, about 40 percent more than vertical. Facing east and west the gain is smaller and the best tilt is very flat. The east-west array yields 858 kWh per kWp lying flat, 508 vertical. A tilted module does stick out further from the railing and can shade the space below or the balcony underneath; factor that in.
Summer and winter: is it worth adjusting?
In summer a flat tilt wins, in winter a steep one. From December to February the maximum facing south is at 60 to 70 degrees with about 124 kWh per kWp, and even vertical, at 115 kWh, beats 30 degrees at 105 kWh.
If you adjust twice a year, 30 degrees from April to September and 60 degrees from October to March, the same data gives 1044 kWh per kWp. Fixed at 40 degrees it is 1017 kWh. Adjusting therefore gains about 2.7 percent. Whether that is worth the effort is best judged by your mount.
Shading: strongest in winter
Tilt only helps if the sun reaches the modules at all. At noon on the shortest day the sun stands only about 15 degrees high in Kassel, about 39 at the equinox and about 62 degrees on the longest day. A building across the street whose top edge sits more than roughly 15 degrees above the horizon, seen from your module, blocks direct sun even at noon in midwinter. In summer the sun passes above the same building.
Because vertical south modules have their edge precisely in winter, this kind of shading weighs more on a balcony than on a roof. Add the shadows the table doesn't know: the balcony slab above, a parapet in front of a propped-up module, trees that only carry leaves in summer. Depending on the wiring, a partly shaded module can lose more power than the shaded area suggests. Which direction yields how much is covered in the guide balcony solar orientation.
