How often should solar panels be cleaned in Sydney?
Quarterly for homes near the harbour or coast, six-monthly for inland Sydney. Salt haze rebuilds the film on coastal glass within months; inland roofs with regular rain can stretch the interval to six. The stakes are measurable: the US National Renewable Energy Laboratory puts typical soiling loss at about 5% of annual output — up to 25% in the dirtiest locations.
Quarterly near the water, six-monthly inland
Sydney splits neatly in two for this. If your house sits within salt range of the harbour or the ocean — Mosman, Manly, Vaucluse, Bronte, anywhere the morning haze tastes of the sea — quarterly is the honest interval. The film on the glass is not just dust; it is a greasy salt layer that rebuilds within months. Inland — St Ives, Gordon, most of the upper North Shore ridge — six-monthly holds, because regular rain rinses the loose stuff between visits.
The interval is doing one job: keeping average soiling low. A panel does not lose output on cleaning day; it loses a little every sunny day the film sits there, and the film only thickens. Clean quarterly and the glass spends most of the year near its best. Stretch a coastal roof to annual and it spends most of the year taxed. The location decides how fast that tax accrues — the calendar just has to keep up.
The maths behind the interval
The best numbers on soiling come from the US National Renewable Energy Laboratory, which monitors it across hundreds of sites. NREL puts typical soiling loss at about 5% of annual output, with the dirtiest locations losing up to 25%. That range is the whole argument for matching interval to location: a regularly rinsed inland roof lives near the low end of it, while a salt-hazed coastal array drifts toward the ugly end if nobody intervenes.
The napkin version: take your system size and your usage and feed-in rates, then shave 5% off annual generation — that is the typical cost of doing nothing. A schedule does not eliminate soiling; it resets the film before it compounds. Quarterly on the coast keeps the glass young. Six-monthly inland does the same where rain carries more of the load. Either way, the recovered yield on a decent-sized system covers the cleans — which is the only maths that matters.
What rain does, and the two things it cannot
Rain is a genuine cleaner of loose dust, which is exactly why it misleads. A proper downpour after a dry fortnight visibly freshens an array, and homeowners reasonably conclude the weather has the job covered. It does not. Rain only removes what water alone can lift, and the losses that matter come from the layer water alone cannot touch. That layer is what a scheduled clean exists for.
Two things survive every storm. The first is the grime strip along the bottom edge of each panel, where runoff pools against the frame and dries — and because panels are wired in strings, a soiled band across one edge drags down more than its own share of the array. The second is anything baked on: bird droppings, lichen, the greasy salt film near the coast. Both need a soft brush and purified water, applied by someone standing on your roof. Which is why they are still there.
Signs your roof is on the fast schedule
Some roofs earn the quarterly cadence without a water view. Big trees overhead mean pollen, sap and bird traffic all year. A shallow panel pitch sheds water slowly, so grime dries where it lands instead of running off. Main-road dust and nearby construction add their own film. If two of those describe your roof, treat it as coastal for scheduling purposes, whatever the postcode says.
And be honest about what a clean can fix. Cleaning recovers output lost to soiling — nothing else. If generation stays low after the glass is spotless, the problem is shading, panel degradation or the inverter, and no amount of brushing will move that number. A good cleaner will tell you so from the roof rather than book you in again. That distinction is worth more than the clean itself.
Put it on the calendar once, then stop deciding
The point of an interval is that you stop weighing it up every season. Solar cleaning is quoted per job — size, pitch, access and growth all move the number — and it pairs naturally with roof and gutter work on the same visit, where bundling saves 5-15%. For homes that want the cadence handled entirely, solar sits inside the Schmick Plan as scheduled work: Keep at $89 a month, Care at $179, Full Schmick at $329.
Or just get your number now. The instant quote returns a firm, bookable price in about 60 seconds — answer a few questions about the roof and the array, and the price holds unless the place turns out materially different. Set it quarterly if you can see the water, six-monthly if you cannot, and let the panels get back to the only job they have.