Solar panels
Solar panels and snow in Andorra: winter output, roof snow load and cleaning
Cold is not the problem; snow and mountain shade are. What happens when it snows, how the structure should be designed and why you should stay off the roof.
· 4 min read · Andorra Servei
Solar panels work through the winter in Andorra, often very well on clear, cold days, but snow stops them completely while it covers them. The good news is that on a well-tilted installation snow usually slides off by itself after a few hours of sunshine. What you should not do is climb onto the roof to clear it: the risk to people and to the panels is far greater than the energy lost over a few days.
Cold yes, snow no
A photovoltaic panel performs better the colder it is, because cells lose efficiency as they heat up. That is why a cloudless January morning with clean mountain air can deliver surprisingly high output. What cuts winter production is not the cold but two other things:
- Fewer hours of sunshine, with the sun lower in the sky.
- Shade from the mountains. In narrow valleys some orientations get direct sun late and lose it early through the middle of winter. It is the factor that most separates one house from another within the same parish.
So before installing we study the real horizon from the roof, not just the orientation. A well-oriented roof shaded by a hillside in December can produce less than a worse-oriented one with an open view.
What happens when it snows
Even a thin layer of snow leaves a panel with almost no output. The glass, however, is smooth, and the light that passes through the snow warms the surface slightly. On panels with generous tilt, snow begins to slide as soon as the sun comes out. On flat or shallow installations it can stay for days.
Systems with monitoring show this clearly: the curve drops to zero on snowy days and recovers once the snow slides off. If many sunny days pass and one panel still produces nothing, that is when it is worth having it checked.
Snow load on the roof
This is where a properly designed installation matters most. Snow is heavy, especially wet snow or snow that has frozen and then been covered by fresh falls. Both the panel mounting structure and the roof itself must withstand the snow load that applies to the altitude and location of the property. When we install, we check:
- That the structure and fixings are sized for the local snow load, not for a coastal installation.
- That anchors pass through the roof covering into load-bearing elements, not just the tiles, and are properly waterproofed.
- That the chosen panels are certified by the manufacturer for the mechanical load required.
- That snow sliding off the panels will not land on a doorway, a pavement or a car: snow guards or barriers are often needed.
How to clear snow, if you really must
The general advice is not to. If the panel can be reached safely from the ground or a terrace (for example a pergola or a ground-mounted array in the garden):
- Use a soft-bristled brush or a rubber squeegee on a long handle.
- Do not use metal shovels or ice scrapers: they scratch the glass.
- Do not pour hot water on it. The sudden temperature change can crack the glass.
- Do not try to remove ice that is stuck on: wait for it to melt.
Climbing onto a roof covered in snow or ice is never worth the risk. If a frozen layer has stayed put for days and you are worried about the weight, call a professional with equipment for working at height.
Solar thermal and heat pumps
Solar thermal collectors for hot water carry an extra risk: the fluid in the circuit. Without the correct proportion of antifreeze it can freeze and crack the collector or the pipework. It should be checked in autumn. If your photovoltaic panels are combined with a heat pump, solar production covers a smaller share of consumption in winter but still helps on clear days. We explain this in more detail on our heat pump page.
Maintenance before winter
- Check the fixings and the condition of the roof around the anchors.
- Clear leaves and dirt that help snow stick.
- Make sure the monitoring works, so you can spot a string of panels that does not recover when the sun returns.
- On solar thermal systems, measure the antifreeze.
If you are thinking about installing panels or want your existing system checked before the first snowfall, see our solar panel service in Andorra and write to us through the contact page. To give you useful guidance, send a photo of the roof and tell us the parish and which way it faces.