Does Cleaning Solar Panels Actually Increase Output?
Published June 22, 2026 by AG Windows and Gutters
Yes, and in the dry South Bay summer the difference is bigger than most homeowners expect. Here's what the numbers look like.
Solar panels lose production gradually, which is exactly why the loss goes unnoticed. Dust, pollen, and bird droppings build a haze that blocks light before it ever reaches the cells.
How Much Output You Lose
Most South Bay arrays we clean regain 10–20% of production. Panels that have gone two or more years without cleaning, or that sit under trees with bird activity, can be down 25% or more. Bird droppings are the worst offender because they create hard shading that can knock an entire string of cells offline.
Why Rain Isn't Enough
California summers are long and dry, and when rain does come it often leaves its own mineral spotting as it evaporates. Rain rinses loose dust but does nothing for bonded pollen, sap, or droppings.
How Panels Should Be Cleaned
Deionized water and soft-bristle brushes, applied with water-fed poles from a safe roof position. No detergents, no abrasives, no high-pressure spray, all of which risk seals and warranties. Nobody should ever be walking on the panels themselves.
- Once or twice a year for most homes
- Quarterly under trees or with heavy bird activity
- Always deionized water so panels dry spot-free
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