Is my roof good for solar? The free answer in 5 minutes
Before contacting an installer — before even starting to compare quotes — there is an official, free tool, funded by the Confederation, which analyzes your roof with very precise LiDAR data. Here's how to use it.
Many homeowners are hesitant to contact an installer because they fear being “engaged” in a sales process before they even know if their project is viable. This is a legitimate fear. The good news: you don't need an installer for an initial assessment. The Swiss state has solved this problem.
Sonnendach.ch — the official Swisstopo tool
Sonnendach.ch (literally "solar roof" in German) is the official platform of the Swiss Confederation for evaluating the solar potential of buildings. It is developed and maintained by Swisstopo (the federal office of topography) in collaboration with the SFOE.
The tool uses LiDAR (Light Detection and Ranging) data — an aircraft-based laser scan that measures the elevation of ground and buildings with an accuracy of a few centimeters. From this data, Sonnendach calculates the orientation, inclination and shading zones of each roof section and translates them into annual solar production potential.
How to use Sonnendach step by step
Go to Sonnendach.ch
The site is available in French, German and Italian. No registration required.
Enter your address
The map centers on your building. You will see your roof colored according to its potential — dark green = excellent, red = poor or unsuitable.
Click on your roof
A side panel opens with specific data: orientation (azimuth), inclination, usable surface area, annual irradiation in kWh/m², and identified gray areas.
Read the 3 key figures
The platform gives you directly: estimated annual solar production (kWh/year), maximum installable power (kWp), and estimated annual CO₂ savings.
Compare with your consumption
If your EWZ or Romande Energie invoice mentions your annual consumption (in kWh), you can directly see if your roof can cover 50%, 80% or 100% of your needs.
How to read the results
The platform ranks each roof on a scale. In practice:
Very good potential
> 900 kWh/m²/yearRoof well oriented due south or slightly southwest/east, with little shade. Excellent profitability.
Good potential
700–900 kWh/m²/yearEast or west orientation, less inclination. Good profitability — to be calculated with your profile.
Average potential
500–700 kWh/m²/yearNortheast or northwest orientation, partial shadows. Project possible but sensitive to the price of the panels.
Low potential
< 500 kWh/m²/yearRoof facing north, heavily shaded, or unfavorably inclined. Not recommended unless special configuration.
Limitations of Sonnendach — and what it doesn't replace
Sonnendach is an excellent pre-screening tool — not a definitive simulation. It ignores the condition of your roof (materials, waterproofing, bearing capacity), the constraints of your interior electrical network, the presence of skylights, chimneys or antennas which create local shading, and the rules of your municipality or PPE which may limit the installation.
A good installer will do a precise simulation with your real data (via Meteonorm or PVsol) during the inspection appointment. Sonnendach gives you confidence or saves you from wasting time — that's his role.
Our recommendation: If Sonnendach gives you a "good" or "very good" potential on the majority of your roof surface, without hesitation ask for 3 quotes from SUISSETEC certified installers. The potential is there — all we have to do is optimize it.
Resources
Sonnendach.ch — Official Swisstopo/SFOE platform. energies-renouvelables.ch — Subsidies by canton. pronovo.ch — Unique Remuneration.
Frequently asked questions
What does Sonnendach.ch show?+
The tool provides an indicative estimate of the solar potential of a roof based on geographic and sunshine data. It does not replace a technical study of the building.
Does Sonnendach replace a visit from an installer?+
No. It does not alone check the condition of the roof, the statics, the electrical installation, local constraints or the connection. Use it as your first step.
What figures should you compare with your bill?+
Compare the indicative annual production and the possible power with your annual consumption, then request a local simulation which takes into account your uses and your prices.