Swiss solar power cannot be judged by a photo of a snowy roof
A project in Valais, in the Oberland or on the Plateau cannot be reasoned out of the same way. In winter, three effects must be separated: the level available irradiation, the performance of the panels in cold weather, and losses linked to snow that actually remains on the roof.
Many homeowners overestimate the negative effect of snow and underestimate the importance of inclination, orientation and profile of winter consumption. Here is a simple method to judge the subject.
The method in 5 steps
Locate your building in its true climate zone
Start by classifying the site: Plateau, Jura, valley alpine, pre-alpine zone or high altitude. The fogs lowland, reverberation in the mountains and duration snow cover do not have at all the same effect depending on the Swiss regions.
A serious estimate must start from the precise location, not of a national average.
See if the snow stays, or if it slides quickly
The slope of the roof, the orientation, the type of covering and access to the sun change everything. A well-sloped roof often clears more quickly than one imagines, while a slightly sloping roof keeps a layer longer penalizing.
We must therefore reason in days of coverage real, not in number of snowfalls.
Isolate winter production in your simulation
Request a monthly simulation and view separately November to February. It is this slice which will tell you if your project provides real support in the cold season or if it remains mainly a summer machine.
For a house heated electrically or equipped with a PAC, this point counts more than annual production overall.
Check the planned technology and operation
In cold weather, photovoltaic modules work often well. On the other hand, seasonal shading, low solar angles and repeated snow episodes must be integrated into the choice of architecture electrical and monitoring.
On some sites, the priority is less to add panels than to avoid misdiagnosed losses in winter.
Decide on use value, not a winter myth
The right question is not "is it snowing?", but "how much of my winter bill can I relieve, and with what regularity?" In several regions Swiss, solar remains relevant despite the winter because it already significantly reduces the bill for the rest of the year.
In other words, we must arbitrate with data monthly, not with weather intuition.
The most common trap
The classic reflex consists of judging an Alpine project by only looking at the worst days of January. This is a mistake. A project photovoltaic is judged on its annual curve, on the speed of recovery after a snowy episode and on the consistency between production and the needs of the building.