Distribution of solar radiation, From Nielsen, R. 2005, 'Solar Radiation'
Distribution of solar radiation, From Nielsen, R. 2005, 'Solar Radiation'

Insolation - weather

Insolation describes the average solar energy received on a given surface area in a given time in watt per square meter (W/m²). Insolation and subsequent solar energy captured by solar panels is highly dependend on the weather. 


On average, each square metre of the upper regions of the atmosphere receives 342 watts of solar radiation (W/m²). The atmosphere absorbs on average 67W/m² and reflects 77 W/m². About 198 W/m² reaches the Earth's surface, of which 168 W/m² is absorbed and 30 W/m² is reflected back to space. The total of the reflected radiation is 107 W/m², or 31% of the incoming radiation (Nielsen, R. 2005, 'Solar Radiation').


extraterrestrial incoming radiation


The accesable solar radiation (Watt/m²) may significantly vary depending on local weather conditions and season. Insolation on a clear summer day can be up to 20 times higher than on a cloudy winter day.


Average solar radiation for a location on the northern hemisphere with a latitude angle of 47° - 55°.


    • sunny, clear sky 
      • summer: 600 - 1000 W/m²
      • winter: 300 - 500 W/m²
    • sunny, skattered clouds or partly cloudy
      • summer: 300 - 600 W/m²
      • winter: 150 - 300 W/m²
    • cloudy, fog
      • summer: 100 - 300 W/m²
      • winter: 50 - 150 W/m²

(Quelle: Wikipedia)