Typical 5 watt solar panel is 25x25 cm. That 5 watt is generated under ideal conditions, i.e. in sunlight, measuring about 100 kilolux. Bright indoor lightning

Typical 5 watt solar panel is 25x25 cm. That 5 watt is generated under ideal conditions, i.e. in sunlight, measuring about 100 kilolux. Bright indoor lightning is 1 kilolux, i.e. the "indoor solar panel charger" would take ~6 m² (assuming ideal spectrum).