How to spot soiling losses in a PV plant

As dust, pollen, bird droppings or industrial particles build up on the module surface, less light reaches the cells. Because the loss develops slowly, it is easy to miss on a daily energy chart.

The traces it leaves in data

• Performance ratio declines gradually over days or weeks; there is no sudden break.
• The decline usually appears similarly on most inverters in the same area.
• PR recovers noticeably after rain or washing. That recovery is the strongest sign the loss came from soiling.
• The loss spreads across the whole day; it does not concentrate at certain hours as shading does.

Telling it apart from shading and faults

Shading repeats at the same time window every day, mostly on specific inverters. A fault shows up as production stopping or dropping sharply. Soiling, unlike both, is a slow, widespread loss that reverses with cleaning.

How this helps with cleaning decisions

Cleaning has a cost. Seeing the size of the loss in kWh helps you plan cleaning by data rather than by calendar. m4chanical GES calculates the estimated energy loss for each event from the gap between expected and actual output.

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