Rinse a panel when the change on the glass is a film. Stop when the change is a burnt cell, a crack, a yellowed backsheet, or a hot spot. Washing is for dirt. Damage goes into photographs and, when the contract applies, into a claim. Scrubbing a crack does not close it. Scrubbing a burnt cell does not restore it.
| What you see | What to do |
|---|---|
| Even dull film, pollen, or dust | Wash only if the cleaning article's safety rules are met |
| A brown or burnt cell | Stop. Photograph it. Treat it as a hot-spot question, not a rinse |
| A crack in the glass | Stop. Photograph it. Keep people off that module |
| A yellow or chalky backsheet | Stop. Photograph what you can see safely. This is a claim file |
| A hard shadow from a vent, tree, or leaf | Shade or local cover, not a uniform film. Identify which before you wash |
Film, and the day you are allowed to wash
Uniform dust, pollen, and a dull haze are soiling. Pacific Northwest National Laboratory's solar guide calls panel soiling the biggest operations issue it covers and says the film is often hard to see: Pacific Northwest National Laboratory. Wash only when how to clean solar panels says the roof, the weather, and the method are safe. If that page says to stay off the glass or to wait, leave the film. A low month can be dirt, and it can be cloud. Compare with the production record before you schedule a wash as a repair.
Bird droppings and a stuck leaf are local. They shade a few cells and they soil the glass. If the cell under the spot looks burnt after the debris is gone, or if it looked burnt before you touched it, stop treating the spot as dirt. A thick patch can run hotter than a uniform film. The burnt mark is the damage row in the table.
Marks that washing will not undo
A brown cell, a crack that catches the light, and a backsheet that has turned yellow or chalky are damage. What a hot spot is owns the overheated cell: how a local defect or a local shadow can heat one spot, and why that is not a cleaning tip. A shadow from a vent or a tree is shade. How shade affects PV output is that loss. Washing the glass under a chimney shadow does not move the chimney.
Photograph damage for the warranty folder: the mark, the label, and the date. What else that folder needs is in what to save for a solar warranty claim. Slow loss of output over many years is a different subject, held in how long solar panels last. A crack is not that slow study. Do not walk the array to see the backsheet if the roof is unsafe. A photo from a safe place, or the installer's photo, is the file. Leave electrical tests of a cracked module to a qualified person.
Streaks at the frame, cement dust from a nearby job, and pollen that coats every module the same way are still film, provided the glass is intact. A single module that looks burnt while its neighbors are only dull belongs on the damage row. Compare neighbors before you book a wash for the whole array. The person on the roof has to be able to work there safely, which is the cleaning article's limit. From the ground, a dated photo is enough to choose the row in the table.
