How much does output drop when solar panels get dirty?
Annual output loss due to soiling is typically around 5% in NREL measurements; it varies between 3% and 25% depending on site conditions. While in humid climates the annual loss stays below 2%, in arid desert sites it rises to 10-15% and above. The daily accumulation rate is between 0.01% and 0.5%.
Soiling loss cannot be reduced to a single figure; the site's dust load, rainfall regime and environmental sources are decisive.
- Typical annual loss: approximately 5% in NREL studies; range 3-25%.
- Climate difference: below 2% annually in humid regions, 10-15% and above in arid desert sites.
- Daily accumulation: between 0.01%/day and 0.5%/day at extremely dusty sites.
- Additional factors: a long dry season approximately 5%, high dust +1-2%, heavy traffic or proximity to a dust source +1%.
The real problem that magnifies the loss is cementation: the panel cools at night, collects dew in the morning, and dust sticks to the surface and hardens. This layer does not come off with rain and requires mechanical cleaning.
The 15-30% gain stated in the ROBEG ELS-03 product description is the instantaneous output recovery measured after cleaning on a heavily soiled panel that has not been cleaned for a long time; it is not an annual average gain. For an assessment specific to your site you can reach us via our contact page.