This is a job defined by what you must not do.
Never a pressure washer
Not on a low setting, not from a distance. Seal damage is cumulative and invisible until the output drops.
From the ground, with a soft brush
A telescopic soft-bristle brush and clean water, ideally deionized so it dries without spotting. If you cannot reach the array from the ground safely, the correct answer is a company with the right access equipment, not a ladder.
Cool glass only
Early morning or evening. Cold water on hot glass thermally shocks it, and hot panels also dry the water into a film before you can clear it.
Nothing abrasive, no detergent
Scouring pads, scrapers and household cleaners all damage the anti-reflective coating, and that loss is permanent and larger than the dirt you removed.
Isolate first
Follow your installer’s instructions for shutting down the array before working on it, and stay off the roof itself.
The questions we hear
Why is a pressure washer forbidden?
Panels are sealed at the frame with an adhesive bead and the cells sit behind glass under a laminate. Pressure at a frame edge drives water past the seal, and moisture ingress is both a performance loss and an electrical risk. Nearly every warranty excludes it explicitly.
Does cleaning actually gain me anything?
In a temperate rainy climate, usually very little on a pitched array — rain does most of it. It is worth doing where panels are near-flat, under trees, near a farm or a busy road, or where bird droppings are shading whole cells.
Last reviewed 2026-08-16
