Question 1

How much production does a dirty solar array actually lose?

Accepted Answer

In the San Joaquin Valley we measure typical losses of 10–20% by late summer, and 25%+ on arrays next to orchards, unpaved lanes or the Highway 99 corridor. The loss is not linear: a thin even dust film costs a few percent, but caked ag dust, pollen crust and bird droppings shade individual cells hard enough to drag a whole string down through the bypass diodes.

Question 2

Why does Exterior Prime rinse with deionized water instead of a hose?

Accepted Answer

Valley tap water carries enough calcium and magnesium to leave a visible mineral haze the moment a panel dries in the sun. That haze scatters light and has to be polished off later. Deionized water is stripped to effectively zero dissolved solids, so the array air-dries spotless with no wiping and no residue on the anti-reflective coating.

Question 3

Can panels be cleaned while the system is producing?

Accepted Answer

Yes, and that is normal. We work in the morning while glass is cool, keep the water stream on the module face rather than junction boxes and conduit, and never open electrical enclosures. If your inverter logs a short production dip during the visit, that is the shading from our brush head passing over a string, not a fault.

Question 4

Will a cleaning fix panels that were already scratched or hazed?

Accepted Answer

No — cleaning removes what is on top of the glass, not damage in it. Micro-scratches from stiff brushes, etching from acidic cleaners and stress cracks from foot traffic are permanent. We photograph anything we find during the pre-clean walk-around and tell you plainly what a cleaning will and will not recover.

Question 5

Do you clean ground-mount arrays and carports too?

Accepted Answer

Yes. Ground mounts and solar carports are usually faster than roof arrays because reach is easy, and they are billed on the same per-panel rate. Ground mounts do collect more splash-back dirt along the bottom edge, so we spend extra time on the lower cell row where soiling loss concentrates.

Question 6

How long does a residential cleaning take?

Accepted Answer

Plan on 45–90 minutes for a 20-panel roof array including setup, the deionized rinse and photo documentation. Larger 40-panel systems and split arrays across two roof planes run closer to two hours. You do not need to be home as long as we can reach an outdoor spigot.

Question 7

What if birds are nesting under the array?

Accepted Answer

Cleaning alone will not stop droppings from coming back — pigeons will re-soil a freshly cleaned array within weeks. In that case we quote Solar Bird Proofing at $58 per panel for the mesh exclusion plus the cleanup of the nesting debris, and schedule the panel cleaning after the exclusion so the result actually lasts.

Question 8

How do I know the cleaning was worth it?

Accepted Answer

Two proofs. First, before-and-after photos of every roof plane land in your inbox the day of the visit. Second, check your monitoring app over the following clear week and compare it to the same window before the clean — recovered soiling loss shows up as a step change in daily kWh, not a slow drift.

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