Dust is costing you production
Arizona gets a lot of sun, and many San Tan Valley rooftops have solar panels. What the sales pitch usually leaves out is soiling: panels only produce from the light that actually reaches the cells, and a film of desert dust sits directly between the two.
This is a real issue here. Monsoon storms deposit fine dust across every roof in the valley, and because meaningful rain is rare the rest of the year, nothing washes it off. It just accumulates, season over season.
The frustrating part is how invisible it is. Panels don't announce a problem. Production drifts down, and unless you're watching your monitoring app closely against previous years, it reads as normal.
Why not just hose them off
Two reasons, and both matter.
Hard water makes it worse. Spraying mineral-heavy tap water on a hot panel and letting it dry deposits exactly the kind of film you were trying to remove, the same problem covered on the hard water page, except now it's on the surface you need light to pass through.
Panels scratch, and warranties have terms. Abrasive pads, harsh chemicals, and pressure washers can damage the anti-reflective coating and, in some cases, affect warranty coverage. Dragging a hose across a roof is also how tiles get cracked and how people get hurt.
What gentle panel cleaning looks like
- Purified or softened water, so nothing is left behind when it dries
- Soft brushes and water-fed poles, no abrasives, no pressure washing
- Cleaning done early or late, not on panels that are hot in the middle of the day
- Roof walked carefully, or reached from poles where tile makes that safer
How often
For most San Tan Valley homes, once or twice a year is enough, and the most valuable single cleaning is right after monsoon season ends, when panels are carrying a full season of deposited dust heading into the sunny fall and winter months.
It pairs naturally with a window cleaning visit, since the equipment and the water are already on site.
Common Questions
Does cleaning panels actually increase output?
Panels produce from the light that reaches the cells, and desert dust sits directly in the way. In a climate with this little rain, that film builds up, and nothing washes it off between monsoons. The effect is gradual, which is exactly why most people never notice it.
Can I just hose my panels off myself?
It usually makes things worse. Tap water in this area is hard, and spraying it on a hot panel leaves that mineral behind when it flash-dries. You also risk cracking tile, damaging the panel coating, and falling off a roof.
Will cleaning void my warranty?
Abrasive pads, harsh chemicals, and pressure washers can affect coatings and warranty coverage. Check your panel warranty, and ask the cleaner what methods they use.
When is the best time to do it?
Right after monsoon season ends. Panels are carrying a full season of deposited dust heading into the bright, clear fall and winter months when they would otherwise produce best.