Smoke hanging over the Diablo Range means ash is landing on every rooftop in Contra Costa and Alameda counties. If you have solar, that includes your panels.
What wildfire ash does to solar panels
Ash is not the same as dust. Dust is loose particulate. It sits on the glass and reduces light transmission, but rain can move it. Ash from wildfires is different: it contains combustion byproducts, including carbon, mineral salts, and organic acids. When ash settles on warm glass and then gets hit with dew or light moisture, it starts to chemically bond to the surface.
That bonded layer does two things. First, it blocks incoming sunlight, reducing the energy your panels can generate, and because ash lands in opaque patches it shades whole cells rather than dimming the panel evenly, so the output hit is disproportionate. Second, and worse: if the ash sits long enough and gets wet repeatedly without being properly removed, it can etch into the anti-reflective coating on the glass. That etching is permanent. Rain doesn't fix it. A garden hose doesn't fix it either.
The 4-6 week window
There's a practical response window after a wildfire event. In the first few days, ash is dry and relatively loose. Wait 4-6 weeks through typical Bay Area fog cycles, and it's a different problem.
Mitch McKay at Total Solar Cleaning has seen panels come in for cleaning weeks after a major smoke event where the ash had bonded so thoroughly that standard cleaning couldn't fully restore the glass clarity. Panels treated within two weeks of a smoke event clean up completely. Panels treated after two months of Bay Area morning fog cycles sometimes don't.
This is why response time matters. The bigger risk isn't a few weeks of lost production, it's the permanent etching: if ash bonds and etches the anti-reflective coating, the damage is irreversible, can void your manufacturer warranty, and compounds over the 25-year life of your panels.
Why a garden hose isn't enough
A lot of homeowners try to rinse ash off themselves, and the instinct makes sense. The problem: tap water in the East Bay has high mineral content. When you hose down a warm solar panel and that water evaporates, it leaves calcium and magnesium deposits on the glass. You've removed some ash and replaced it with a mineral film that's just as hard to deal with.
Professional cleaning uses deionized water. All minerals and dissolved solids are removed before the water touches your panels. It rinses clean with zero residue. This is the method recommended in the maintenance guidance of SunPower, Tesla/SolarCity, LG, Panasonic, and every other major panel manufacturer.
Beyond water chemistry, ash removal requires physical contact with the glass. A soft-bristle brush system dislodges the bonded particles while the deionized water carries them away. A garden hose at pressure can't replicate this, and pressure washing can crack panels and void warranties.
What about smoke without visible ash?
Heavy smoke events can deposit ash that isn't visually obvious. You won't necessarily see a gray coating. If your solar monitoring app is showing a production drop after a fire season event, that's the signal. Don't wait for panels to look dirty.
For homeowners in Orinda solar panel cleaning and Lafayette solar panel cleaning territory, who are closer to the wildfire corridors in the hills, the exposure is higher. East Bay hill fires move fast and ash deposits heavily on the western-facing slopes of Contra Costa. If you're in those zip codes, treat any significant smoke event as a cleaning trigger.
For homeowners in Concord solar panel cleaning service area, the distance from the fire corridors is greater, but summer smoke from the Diablo Range and Vaca Mountains still reaches the valley floor. Production monitoring is your best diagnostic.
After a smoke event: the right sequence
Don't clean panels the same day as heavy ash fall. Let the ash settle and the air clear first. Then schedule cleaning within two weeks if the smoke event was significant.
If you're not sure whether your event qualified as significant, check your inverter data or monitoring app. A drop of 10% or more compared to a clear-sky day is meaningful. The FAQ on post-wildfire cleaning has more detail on how to read your production data.
For Walnut Creek solar panel cleaning customers who ask whether one rain after a smoke event is enough: it isn't. Rain moves dust. It doesn't remove bonded ash.
Scheduling after a wildfire event
Total Solar Cleaning gets busy after major smoke events. Schedule quickly if you want a slot in the two-week response window. Mitch's team serves the entire East Bay, so lead times can run 3-7 business days depending on demand.
Call (833) 444-4173 to schedule or get a quote. You don't need to be home for the cleaning. Leave the gate unlocked and Total Solar Cleaning handles the rest.