SolarMapped › Sources
Sources and method
SolarMapped turns public solar-resource data into something you can read at a glance. This page lists what we use, how we use it, and what the numbers do and don’t mean.
Solar estimates: PVGIS
All solar figures come from PVGIS (Photovoltaic Geographical Information System, version 5.3), provided by the European Commission, Joint Research Centre (JRC). PVGIS combines satellite-derived and reanalysis weather data with a PV performance model. The report uses PVGIS’s PVcalc tool. PVGIS picks the most suitable radiation database for each location, and the report shows which one was used (for example PVGIS-SARAH3 in Europe, Africa and Asia, PVGIS-NSRDB in the Americas or PVGIS-ERA5 elsewhere) along with its year range.
Requests go from your browser to SolarMapped’s own API, which calls PVGIS, converts the answer to our format and caches it. Coordinates are rounded to 0.01° (about 1 km) before calculating and caching.
Map layer
The colours on the map show annual PV output in kWh per kWp per year for fixed panels at their optimal tilt. The layer was generated by running the same PVGIS calculation on a 2° global grid (4,316 land points, values from 557 to 2,373), then smoothing between points and projecting to the web map. It is a regional overview: it will not show local effects such as valleys, shading or coastal fog, which the location report can. The layer was last generated on 21 September 2026.
Calculation assumptions
| PV technology | Crystalline silicon |
|---|---|
| System size | Calculated for 1 kWp and scaled linearly to your chosen size |
| System losses | 14% (cables, inverter, dirt, ageing and similar). Temperature and reflection losses are modelled separately by PVGIS. |
| Mounting | Fixed, free-standing |
| Orientation | Facing the equator: south in the northern hemisphere, north in the southern |
| Tilt | Optimised by PVGIS for the location |
| Shading | Terrain horizon from a digital elevation model, where available. Buildings and trees are not modelled. |
| Weather | Long-term multi-year averages |
These are model estimates, not an installer quote or a roof-specific simulation. Real output depends on the actual roof, nearby shading, equipment, and the weather in a given year.
Qualitative labels
The label next to a result (for example “Good”) is a fixed, worldwide banding of kWh/kWp/year. It is not relative to the country or region, and the map legend uses the same bands.
| Label | kWh/kWp/year |
|---|---|
| Low | below 700 |
| Moderate | 700 to 1000 |
| Good | 1000 to 1300 |
| Very good | 1300 to 1600 |
| Excellent | 1600 to 1900 |
| Exceptional | 1900 and above |
“Optimal orientation” is reported as the direction facing the equator and “optimal tilt” as the fixed angle from horizontal that maximises annual output in the model.
Place search
Place names and search results come from Nominatim, the search engine for OpenStreetMap data, operated by the OpenStreetMap Foundation under its usage policy. Searches run when you submit the form (not as you type) and results are cached. Data © OpenStreetMap contributors, available under the Open Database Licence (ODbL).
Basemap
Map tiles are served by OpenFreeMap using the OpenMapTiles schema, with data © OpenStreetMap contributors. The map is drawn with MapLibre GL JS.
Updates
Solar-resource averages change slowly. The map layer was generated on 21 September 2026 using PVGIS 5.3; the per-location report uses the same calculation, cached for up to 30 days and versioned so improvements to the method never mix with older results.