Panels out by Nampa Municipal Airport get loaded from three directions at once: field silt off the farm ground west of the runway, dust kicked up off gravel drives and shop approaches, and construction dirt along Garrity Boulevard. It builds as an even haze, which is the kind that quietly costs you output all summer.
The dust in Airport District is fine agricultural silt, not the coarse grit you get off a paved subdivision street. Coarse grit mostly rinses. Fine silt bonds to the glass with morning dew and dries into a thin, even film that shades every cell a little instead of blocking one spot outright, so nothing on your monitoring app looks broken — production just drifts down week over week. The northwest wind reloads panels within days of a rain, and spring adds pollen on top of it, especially on the properties with mature trees around the house. If you have a gravel drive or an unpaved approach to a shop, the array over that end of the property loads faster than the one over the house. We won't promise you a recovery percentage before we've looked; we'll tell you what we actually see on the glass.
Plenty of Airport District properties have panels on a shop, a detached garage, or a low single-story roofline, and on the bigger non-HOA lots the irrigation is set to throw far. When a rotor reaches the low edge of an array, Nampa water — up to around 7.08 grains per gallon — dries on the glass and leaves mineral scale. That is not dust and it does not wash off with a rinse. Scale is also cumulative: each cycle adds another layer, and by the second or third season it has etched enough to stay visible. If you see hazy white banding only along the bottom row of panels and the top rows look fine, that is your sprinkler, and the fix is retiming or re-aiming the head — otherwise we'll be back cleaning the same band every visit.
Most houses here went up during Nampa's growth run through the 1990s and 2000s, which usually means a moderate gable pitch — steep enough that a panel sheds most of a hard rain, shallow enough that it holds dust and pollen between storms. That middle pitch is the worst case for self-cleaning: too flat to shed film, too steep to walk casually. We work these from ladder and pole where we can and stay off the modules entirely; panel glass is tempered but the cells under it crack from point loading long before the glass does, and microcracks do not show up until production drops. On the older acreage homes toward the county edge, ground mounts and shop-roof arrays are common and are usually easier and faster to quote than a two-story roof array.
We clean panels with 100% pure deionized water, the same water we use on glass. Zero dissolved minerals means nothing is left to spot as it dries, and no soap means no surfactant film sitting on the modules after we leave. That last part matters more on a solar array than on a window: any residue left on the glass becomes the surface the next round of field silt sticks to, so a soap-washed array reloads faster than one rinsed clean. We use no abrasives, no scrubbing pads, and no pressure washer on modules — pressure drives water past the frame seals and at the junction box, which is a warranty problem you do not want. Gutters and hardscape on the same property get standard soft-wash and pressure methods; panels never do.
Cleaning gets back the output you lost to soiling. That is the whole list. It does nothing for panel degradation — modules lose a fraction of a percent of their rated output every year and that is permanent chemistry, not dirt. It does nothing for shading. If the trees you planted when the house was new now clip the array from mid-afternoon on, clean glass will not buy that back; that is a trimming job or a panel relocation. It does nothing for a failed optimizer, a tripped string, or an inverter fault, and if one panel reads far below its neighbors on a clean, sunny day, that is electrical and you want your installer, not us. If we get on site and the array is genuinely clean, we will say so and you will not be charged for a cleaning you did not need.
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For most Airport District properties, twice a year works — once after spring pollen and once in late summer when field dust has been blowing for months. If you are on a gravel drive, next to active construction on Garrity, or have irrigation reaching the array, you will likely want quarterly. Watch your production data across a dry stretch; a steady drift down with no weather explanation is soiling.
That pattern is almost always sprinkler overspray, and the answer depends on age. Fresh mineral scale comes off with pure water and dwell time. Scale that has been baking on for two or three seasons has etched the glass surface and some of it stays, no matter what we do. We will get what is removable and tell you honestly what is permanent. Retiming that sprinkler head is what actually stops it.
Usually in your favor. Shop and detached-garage arrays are typically single-story with easier ladder access, so they quote lower than a two-story roof array with the same panel count. We quote per array, so tell us up front how many separate arrays you have — house, shop, ground mount — and roughly how many modules in each, and we can give you a real number instead of a range.
Neither. We work from ladder and pole and stay off the modules. Panel glass is tempered and feels solid underfoot, but the cells beneath it crack from point loading, and those microcracks only show up later as lost output. Pressure washing is worse — it forces water past the frame seals and around the junction box. Both are avoidable ways to turn a cleaning into a warranty claim.
Only if the drop is from dirt. Soiling loss comes on gradually and affects the whole array evenly. A sudden drop, or one panel or one string reading far below the rest on a clear day, is electrical — a failed optimizer, a tripped string, an inverter fault — and that is a call to your installer. Shading from grown-in trees is also not a cleaning problem. We will tell you which one we think you have.
Yes, and it is worth bundling given the drive. Windows get the same pure deionized water as the panels. Gutters and any hardscape get standard soft-wash and pressure methods — those tools never touch the modules. We run same-day and next-day slots to this part of Nampa most weeks, and memberships are monthly or quarterly with no contract. Fully insured, locally owned.
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