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Solar Panel Cleaning

Why Dirty Panels Lose Output

Dust, pollen, soot, and droppings block light from reaching the cells. Even a thin film lowers output, and a patch of grime on one cell can drag down a whole string. In an NREL study of pollen at utility scale plants, performance fell by as much as 15 percent in peak season, and rain did not fully restore it (NREL on pollen and solar panels). Losses at a home depend on your climate and roof tilt.

How Often To Clean

EnergySage on solar panel cleaning says most systems need cleaning once or twice a year, and that rainy areas may need less than dry, dusty ones. Heavily wooded areas and places with a lot of bird activity may need more. Solar.com on whether to wash panels discusses when washing pays off.

What Cleaning Costs

Prices vary by region, roof access, and system size. EnergySage says professional cleaning usually costs around $150 to $350 (EnergySage on solar panel cleaning). Solar.com cites a lower figure of about $120 to $140 for an average residential system (Solar.com on whether to wash panels). Treat these as ranges and get two or three local quotes.

What To Ask A Cleaning Company

• Are you insured, and do you carry workers compensation?
• What water and tools do you use? Soft brushes and purified or plain water are typical. Pressure washers and harsh chemicals are not.
• Do you clean in the early morning or evening when panels are cool?
• Will you check for loose wiring, bird nesting, or cracked glass while you are up there?
• Do you follow my panel manufacturer's cleaning guidance?

Also read DIY Versus Professional Cleaning and Bird Proofing.