Many PV plant owners underestimate the impact of soiling. The assumption that "rain will wash it off" is the most common mistake. Doka field measurements consistently show that dirty panels produce 15-25% less energy than clean ones. And dirt doesn't just hit instant production — it shortens panel life.
Immediate impact on production
For sunlight to reach PV cells, the panel must stay transparent. Every deposit absorbs or scatters light. Typical loss figures:
- Light dust layer (1-2 weeks): 3-7% loss
- Moderate soiling (3-4 weeks): 10-15% loss
- Heavy soiling + bird droppings (5+ weeks): 18-25% loss
- Harvest-season agri-PV (pollen + organic residue): up to 25-35% loss
For a 5 MW PV plant, just 10% loss equals 800 MWh of lost production per year and €64,000 in revenue. See our ROI guide for the breakdown.
Permanent damage: dirt eats your panel
Instant losses are recoverable. The real danger is when dirt stays long enough to permanently degrade the panel:
Acidic deposits
Bird droppings and certain industrial residues are acidic. They slowly etch the anti-reflective coating. Once that coating breaks down — no going back. Yield in that area is permanently reduced; panel warranty may be affected.
Hot-spot effect
If just one section of a panel is dirty, that cell doesn't produce — but current keeps flowing to it. The energy turns into heat. This local overheating becomes a "hot spot"; micro-cracks form, cells burn out and ultimately the panel fails.
Water marks and lime
Sites using poor-quality water build up lime deposits that permanently block sunlight. That's why Doka FK robots are optimized for osmosis water.
Cost dimension
At a reference site of ours in the Konya region (2 MW), we measured 320 MWh of lost production due to soiling over the year. Monthly FK-1000 V3 solar panel cleaning robot cleaning recovered 92% of that loss. With this gain factored against annual cost, the robot paid back in a single season.
Conclusion
Leaving your panel dirty doesn't just cost electricity — it shortens the panel's life over years and can void warranty terms. Periodic cleaning protects your investment. Properly scheduled robotic cleaning is the only maintenance line item that preserves both production and panel warranty.