Rooftop Solar Cleaning in Atwell — Restoring Output on an 8-Panel System

Location: Atwell

Atwell sits in Perth’s southern corridor, well within the band of suburbs where rooftop solar installations have become close to standard on residential properties. The combination of high sunshine hours, rising electricity costs, and relatively affordable system pricing over the past decade means most streets in Atwell now have at least several homes generating their own power from the roof.

What’s less visible is what’s happening to the output of those systems over time. Dust, pollen, fine airborne particles and the residue from bore water reticulation accumulate on panel glass continuously — and unlike the windows on the front of the house, most homeowners can’t see their solar panels clearly enough to notice the contamination building up. The panels keep generating, the inverter keeps reporting numbers, and the slow decline in output goes unnoticed until someone actually gets up there and looks.

That’s exactly what happened at this Atwell property — a large rooftop system that was working, but not working as well as it should have been.

The System: What We Were Working With

The photo from this job shows a substantial residential solar installation on a grey Colorbond roof — two rows of panels arranged across the roof pitch, totalling 8 panels in the configuration visible from above. The array is mounted on standard aluminium rail frames, angled to optimise the northward solar exposure that Perth rooftops are typically designed to capture.

In the photo, the cleaning is already underway — the water-fed pole and hose are visible across the panels, and the wet glass shows that deep, saturated blue colour that indicates clean, contamination-free panel glass actively refracting light. The contrast between the panels mid-clean and a fully contaminated array is significant; you can see the clarity in the wet surface that was previously obscured by a layer of bonded dust and atmospheric deposits.

The surrounding streetscape is also visible — established Atwell residential streets, neighbouring rooftops with their own solar installations, and the slightly elevated position that gives rooftop systems in this part of the suburb good solar exposure across the day.

What Accumulates on Panels in Atwell

Atwell is positioned in Perth’s outer southern suburbs, bordered by Cockburn to the north and the Beeliar wetlands corridor to the east. That location creates a specific set of contamination conditions for rooftop solar:

Fine road and construction dust. Atwell and the surrounding suburbs have seen significant development activity over the past decade as the southern corridor has expanded. Earthmoving, construction traffic, and the fine red-brown dust characteristic of Perth’s sandy soils all become airborne and settle on rooftop surfaces. On the horizontal tilt of solar panels, this dust accumulates and compacts rather than blowing clear — particularly in the drier months when there’s no rain to rinse it off.

Pollen from established vegetation. The suburb has a mix of established garden planting and proximity to the Beeliar regional park corridor. During spring and into early summer, pollen loads in the air are significant, and pollen that settles on warm solar glass bonds quickly to the surface. Unlike dry dust, pollen residue doesn’t blow away easily once it’s made contact with a warm panel.

Bore water overspray mineral deposits. A high proportion of Atwell properties use bore-fed reticulation. Reticulation heads that send overspray onto the roof — common on sloped lots where the roof edge is close to the garden — deposit the same dissolved calcium, magnesium and silica onto panel surfaces that we see causing mineral haze on windows. On solar glass, this reduces transmittance and cuts into generation output.

General atmospheric fallout from the Cockburn corridor. Atwell’s proximity to the Cockburn industrial and commercial zones means a degree of particulate fallout from vehicle and industrial activity is present in the local air. Over time this adds a general grey toning to panel surfaces that is distinct from and additional to the other contamination types.

The cumulative effect of all of these sources is a panel surface that, after twelve months or more without cleaning, can be carrying a contamination layer thick enough to noticeably reduce the amount of light reaching the photovoltaic cells beneath.

How Much Output Does Contamination Actually Cost?

This is the question most Atwell homeowners ask when we discuss solar panel cleaning, and it deserves a direct answer.

The research on solar panel soiling consistently shows that contaminated panels in Australian conditions lose somewhere between 15 and 35 percent of their rated output depending on contamination severity, panel tilt angle, and local conditions. Perth’s combination of dry summers with minimal rainfall to self-clean panels, high dust loads, and active reticulation systems puts panels here towards the higher end of that range.

For an 8-panel system like the one on this Atwell property — assuming a typical 3kW system capacity — a 20 percent output reduction represents roughly 600W of generation capacity that simply isn’t reaching the inverter. Over a full year, with Perth’s sunshine hours, that translates to a meaningful loss in both self-consumption and feed-in generation that compounds with every month the panels remain uncleaned.

The economics are straightforward: a professional clean costs a fraction of the value of the lost generation it recovers, and the output improvement is immediate and measurable on the inverter the day after the clean.

We’ve covered the evidence behind this in detail in our solar panel cleaning guide for coastal WA — worth reading if you want the full picture before deciding on a cleaning schedule.

How We Clean Solar Panels

The cleaning process we use on residential rooftop systems is specifically designed around what solar panel manufacturers actually recommend — which matters more than most homeowners realise.

Deionised water only — no detergents. We use a pure deionised water system delivered through a water-fed brush pole. Deionised water has had all dissolved minerals removed, which means when it dries on the panel surface, it leaves absolutely no residue. Regular tap water — even with a squeegee — leaves trace minerals behind that begin the contamination cycle again immediately. Detergents leave a surfactant film that attracts airborne dust faster than clean glass. Deionised water is the only rinse method that leaves panel glass genuinely clean.

Soft brush agitation. The water-fed brush gently agitates the panel surface to loosen and lift contamination without scratching the glass. Solar panel glass is tempered and relatively hard, but abrasive cleaning tools or rough cloths can cause micro-scratches over time that scatter light and progressively reduce panel efficiency. The soft-bristle brush system avoids this entirely.

Frame and edge cleaning included. Dirt, pollen and debris accumulate in the frame channels around each panel, particularly at the lower edge where runoff collects. These channels are cleaned as part of the service — leaving frame debris in place means the first rain event washes it straight back onto the panel glass.

No pressure washing. High-pressure water is not used on solar panels. The pressures involved can force water under panel seals, damage junction boxes, and void manufacturer warranties. Our water-fed pole system delivers water at low pressure — enough to rinse effectively, not enough to cause any damage.

The system is also entirely ground-based for most residential roof configurations — the extension pole reaches rooftop panels without requiring anyone to step onto the roof itself, which is both safer and eliminates any risk of roof or panel damage from foot traffic.