What sort of cleaning regime should I have for a solar energy system, and do PV and solar-thermal panels need to be treated differently?

  • Location, location, location. Many factors are involved: traffic intensity, average rain and wind, angle of the panels, height above the ground, nearby industry,.... Do you have a specific location in mind?
    – user2451
    Commented Jun 17, 2016 at 14:27

4 Answers 4


I only have one anecdote and avague idea: An agrarian schooling center (Haus Düsse) in Germany clean their PV System once a year, and clean/dirty means a difference of 10% effectiveness. However, as this is basically a small farm with lifestock, different grain treatments, lots of diesel vehicles etc. you would expect far more dust there than at a lot of other places. 3 years ago, they were starting to systematically analyze what's the most economic cleaning regime.

  • The anecdotal evidence I've heard here in Montana, USA seems to confirm this. Commented Jun 12, 2013 at 21:52
  • To add another anecdote: I just visited a roof mounted PV system (>50 kW) with a very small roof pitch/slope of say 10°. The operator claimed to clean the modules each year in the springtime as the agricultural workings on the farm foul them significantly. Story 2: I am the "caretaker" of another PV system (18 kW) roof mounted, about 30° slope and we do not clean them on a regular basis as we do not see a significant drop in output power (so far), operational time 'bout five years now.
    – Ghanima
    Commented Mar 5, 2015 at 0:23

I work and attend classes at a University in Florida. Our 100kW system has been installed for more than five years without a single cleaning. I have walked the solar field several times and can confirm that no significant dust has collected. (The angle of inclination is about 27 degrees.) But, Florida rains a lot and that helps keep everything clean. I imagine desert areas with wind storms would be much worse. But a duster at best or some cotton rags and dish-soap at worst would be more than enough to keep any system clean.


I personally calculated the ratio energy to insolation for a friend's home system with shallow angle (15°) in the Netherlands after they got cleaned them for the first time in 5 years and there was no discernible improvement. The uncertainty is about 2% so the improvement must be lower than that.

Conclusion: it is extremely system and location dependent.


It depends on what is fouling the panels, if like us you have Lime trees nearby that drop a sticky residue in summer then you may need to clean the panels more often. We see a 10-15% gain in power generated immediatley after cleaning the panels when they are dirty. The angle of the panel in combination with the amount of rainfall will also affect how often the panels will benefit from being cleaned. To clean the panels we sometimes just spray water on them or if they are heavily fouled we used a telescopic brush designed for cleaning cars.

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