Get the interval right for the North Coast

How Often Should Solar Panels Be Cleaned?

Most solar panels should be cleaned twice a year, and on the foggy North Coast that usually means a spring clean and a late-summer clean. But the right interval depends on your roof, your trees and your microclimate — a shaded home in Arcata builds up moss far faster than an open lot in Fortuna. Here's how to figure out yours.

The baseline

Twice a year is the starting point

Twice a year suits most Humboldt County homes: once in spring to clear winter's moss and pollen, once in late summer to reset before the rains return. That cadence keeps output steady without overpaying for visits you don't need. It's the interval we recommend as a default across the county.

When to go more often

Shaded, tree-heavy roofs need quarterly attention

Shaded roofs under redwoods or firs — common in Arcata, Blue Lake and the hills above Eureka — grow organic film fast and often do better on a quarterly schedule. If your panels sit near constant tree cover or you see green creeping in from the frame edges, tighten the interval. The damp North Coast air feeds that growth year-round.

Signs you're overdue

Watch your output and your frame edges

The clearest sign it's time is a drop in production you can't explain by weather or season. Visible moss, a dulled sheen, bird droppings or pollen haze are the other tells. If you're seeing any of those on your Humboldt County array, you're past due for a clean.

Recommended solar cleaning frequency by roof situation

Roof situation	Recommended frequency
Open lot, few trees (e.g., Fortuna)	Twice a year
Some tree cover	Twice a year, check in spring
Heavy shade under redwoods/firs (Arcata, Blue Lake)	Quarterly
After wildfire smoke or ashfall (inland)	As soon as it's safe