Winter solar efficiency effect in vertical PV systems
- Martin Schmal
- Jan 20
- 2 min read
Why vertical photovoltaics are particularly efficient in winter
Vertical PV systems on green roofs generate significantly more electricity in winter than conventional tilted solar panels.
This so-called winter electricity effect makes vertical photovoltaics a particularly attractive solution for buildings where winter yields, grid stability and self-consumption are the focus.
Vertical PV systems truly reach their full potential when combined with green roofs.
What is the winter electricity effect of vertical photovoltaics?
The winter electricity effect describes the property of vertically (90°) mounted PV modules to deliver relatively higher specific electricity yields (kWh/kWp) in the winter months than inclined roof systems.
Why are vertical PV systems on green roofs superior in winter?
1. Low sun angle in winter (Central Europe)
In Germany, Austria, and Switzerland, the sun is very low in the sky during winter. Classic rooftop solar panels with a 20–30° tilt are therefore not optimally illuminated .
Vertical PV modules, on the other hand, achieve an almost ideal angle of incidence.
2. Albedo effect: Reflection on snow and green roofs
Snow reflects up to 80–90% of the incident light . Vertical bifacial PV modules can actively utilize this reflected light on the back.
Green roofs also enhance this effect:
light substrates
Vegetation in winter
uniform reflection
3. No snow accumulation on vertical modules
A crucial advantage in winter operation:
Inclined modules → snow cover, yield loss
Vertical modules → no snow accumulation
The system remains active immediately even after snowfall.
Why is winter electricity particularly relevant today?
Energy demand increases sharply in winter due to:
Heat pumps
electric heating systems
lighting
increasing electrification of buildings
Vertical PV on green roofs: More than just electricity
The combination of green roof + vertical photovoltaics offers additional advantages:
no competition for space between PV and greening
improved roof ecology
lower surcharge
improved cooling of the modules in summer
architecturally integrable
