SolarClair
How much will your roof produce? A simulator that answers like the European reference, within 1%, and shows its working.
Since October 2026 · launching
Annual gap with PVGIS 5.3
0.95% at worst, across 205 reference cases and 30 sites. The specification allowed 2%.
0.08% on average across the 205 reference cases.
The challenge
PVGIS, the European Commission’s tool, is the reference for solar yield. But it is slow for a new location, unreachable from a browser and silent about money. Consumer simulators, for their part, give numbers nobody can check.
The approach
- An hourly engine in TypeScript, matched to PVGIS down to its unpublished parameters.
- Regression tests: 205 cases compared with PVGIS, with pvlib as a second opinion.
- The roof, measured in the browser from IGN’s LiDAR HD laser survey: roof faces, pitches, obstacles, panels placed one by one.
The numbers
- 205 reference cases, replayed on every engine change
- 30 sites, each with its own terrain shading
- 8,760 hours computed per year, one by one
- 98–100 on Lighthouse, result pages included
Annual gaps with PVGIS 5.3 measured with engine 0.2.0 on 29 October 2026; Lighthouse scores measured the same day on the homepage and a result page.
- TypeScript
- Next.js
- Fastify
- PostgreSQL
- MapLibre
- IGN LiDAR HD
- Playwright
Updated 2 November 2026