There is rarely enough rain here to rinse panels off, so dust lands and stays. We wash with purified water that dries without spotting.
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The Coachella Valley is close to ideal for solar. Enormous sun, long days, and a great many roofs carrying arrays. It is also a low-rainfall desert with constant blowing dust, and those two facts work against each other.
A photovoltaic panel produces from the light that actually reaches the cells. Anything on the glass between the sun and the cell blocks some of that light. In the industry this is called soiling loss, and it is a well-understood factor in system performance. In most of the country it is largely self-correcting, because rain rinses panels regularly enough to keep the effect small. Here, rain is rare enough that it does not do that job. Dust lands, and it stays.
What builds up is not just dust either. Pollen, agricultural drift from the eastern valley, bird droppings, and the mud film left after monsoon storms all end up on the glass. Bird droppings and mud are worse than dust in an important way: dust reduces light across the whole panel fairly evenly, while an opaque patch blocks specific cells entirely, and because of how panels are wired, a shaded section can drag down output well beyond its own area.
The result is that panels here quietly under-produce, and because it happens gradually nobody notices from the roof. It shows in production data rather than in how the array looks.
We wash with purified water, which has had the dissolved mineral removed. That matters here specifically: rinse panels with ordinary valley tap water and let them dry in the sun and you leave mineral spotting behind, which builds into a haze that blocks more light than the dust did. Purified water dries clear. There is also no detergent film left on the glass for the next dust to stick to.
Body weight on a panel can create microcracks in the cells. They are invisible from the surface and they permanently reduce what that panel produces. We work from the perimeter with extension equipment rather than walking the array.
Panel glass in this valley reaches very high surface temperatures under full sun. Cool water on hot glass is a thermal shock risk, and it evaporates on contact, which defeats the purpose. Cleaning happens early for both reasons.
Check your monitoring app or inverter data before the cleaning and again in the days after. Your own production numbers are far more informative than any general claim about percentages, because the effect depends on your array, your dust exposure, and how long it has been. If the difference is not there in your data, you have learned something useful.
Different soiling behaves differently, and some of it matters far more than its appearance suggests.
| Soiling | Where it comes from | Why it matters |
|---|---|---|
| Fine desert dust | Blown across the whole valley year round | Even, gradual, and the largest cumulative factor here |
| Monsoon mud film | Summer storms combining dust and rain | Bonds as it bakes dry, and does not blow off afterwards |
| Bird droppings | Perching on frames and roof edges | Opaque, and can affect output well beyond the area covered |
| Agricultural drift | Farming activity in the eastern valley | Heavier particulate that settles firmly onto glass |
| Pollen and organic debris | Landscaping and seasonal growth | Sticks to glass and holds subsequent dust |
| Hard water spotting | Rinsing with untreated tap water | Self-inflicted, and worse than the dust it replaced |
Scroll the table sideways on a phone.
Panels installed at a shallow tilt, which is common on low-slope valley roofs, shed less on their own than steeply tilted arrays and hold dust more readily. Ground-mounted arrays sit closer to the source of blowing dust and generally need attention more often than roof arrays.
Six stages, deliberately conservative. Almost everything that damages panels comes from someone being in a hurry.
We look at the array layout, roof pitch and access, the type of soiling present, and any visible issues such as damaged panels, loose fixings, or debris caught under the frames.
Work is scheduled early, before the panels have heated up under full sun. This avoids thermal shock and stops water evaporating before it can do anything.
Leaves, seed pods, nesting material, and windblown debris are cleared from the array and from beneath the frames, where it collects and holds moisture.
Soft brushing with purified water across the glass, working from the perimeter. No pressure washing, no abrasives, no detergent, and no weight on the panels.
A final purified water rinse, which dries without spotting because there is no dissolved mineral in it to leave behind.
We tell you anything we noticed: damaged or discoloured panels, loose mounting hardware, evidence of birds nesting beneath the array. We do not do electrical work, but you should know what is up there.
Panels are the rare purchase where you can measure whether maintenance was worth it, because the system reports its own output.
Daily production swings with weather and season, so a single day tells you very little. What is informative is the trend across comparable periods. Soiling loss builds gradually, which is why it hides in plain sight: nobody notices a slow decline, they notice a step change after a cleaning.
The clearest read is production on a clear day shortly before a cleaning against a clear day shortly after, at a similar point in the season. That is your array, on your roof, with your dust exposure, rather than a general figure that may not describe your situation at all.
With extra attention after monsoon storms, which deposit mud rather than loose dust. Arrays near open desert, farmland, a golf course, or an active construction site collect noticeably more and often want a shorter interval.
If output has dropped and cleaning does not change it, look at what has grown. Palms and mature landscaping cast shade that did not exist when the array was installed, and because of how panels are wired, partial shading can cost more output than its area suggests. That is a tree problem rather than a dust problem, and cleaning will not fix it.
Panel cleaning is quoted by array size and access after we have seen the property.
We clean panels. We do not perform electrical work, repair or replace panels, alter wiring, or service inverters. If we see something that concerns us up there we will tell you and you can get your installer to look at it. Anyone who offers to clean your array and also fix its electrical problems is offering two different trades.
We clean solar arrays throughout the Coachella Valley. Tap your city for local notes.
We also reach Thermal, Mecca, and North Shore. Not on the list? Call (760) 567-2548 and ask.
Tell us roughly how many panels and what kind of roof. Check your production data before and after and judge for yourself.