A factory in Bergara with 2,400 m² of south-facing roof, a year of electricity use and shifts from 6:00 to 22:00 on weekdays. Esan opens PVGIS, the European Commission's solar tool, in a browser, puts the building on the map, runs the numbers and downloads five years of hourly production. It crosses them hour by hour with the shifts, sizes the system at 200 kWp with nothing exported to the grid, prices it at today's market and delivers a five-page PDF with a source for every figure: €23,470 saved a year, paid back in about seven.