Is solar panel cleaning actually worth it?
It depends on where the array sits. The US National Renewable Energy Laboratory puts typical soiling loss near 5% of annual output, and up to 25% in dirty, low-rain spots. Near the harbour, bird droppings and a bonded salt film block light and never rinse off in rain — those panels pay back. A flat, rain-washed inland array gains little.
The answer is a postcode, not a yes or no
The question assumes one answer for every roof. There isn't one. The US National Renewable Energy Laboratory, which runs a national soiling-monitoring program, puts typical loss near 5% of annual output — and up to 25% where grime is heavy and rain is rare. The gap between those two numbers is the whole argument. Whether cleaning is worth it is a question about your site — how much grime lands, and how much rain washes it back off — not about solar panels in general.
Two identical systems — same model, same output on the day they went up. One sits on a flat roof in a rain-fed inland suburb. The other faces the harbour at Mosman, low pitch, under the gulls. Five years on they don't produce the same numbers, and a clean is worth it on one and close to pointless on the other. Nothing about the panels changed. The site did the deciding.
The 'never worth it' studies are testing a different roof
A run of studies has concluded that panel cleaning rarely pays for itself, and they get quoted as if the case is closed. Read the fine print. Most tested large, flat, well-tilted arrays in temperate or rain-fed climates, where a good downpour genuinely does most of the work. On that kind of site the conclusion holds — rain is a free cleaner, and paying for more of it buys you very little extra yield.
The trouble is the finding gets pasted onto roofs it never studied. A low-pitch array a few streets from the water is not the roof those papers measured. The honest read of the research is narrow: rain handles loose dust on a well-angled, regularly rinsed array. It says nothing useful about a bonded salt film or baked-on droppings — which is exactly the soiling Sydney's coastline specialises in. Location and the type of dirt decide it, not a blanket rule.
Two kinds of dirt, and only one of them rinses
Soiling isn't one substance. Loose dust and spring pollen sit on top of the glass, and a decent storm carries most of it off — that's the dirt the sceptical studies have in mind. If that's all your panels collect, rain is already doing the job, and you should leave it to. A steeper pitch helps the same way: water sheets down the face and takes the loose film with it.
The other kind doesn't budge. Bird droppings bake on and block the cells underneath outright. Near the harbour, salt drifts in on the morning haze and dries to a bonded film that rain smears rather than removes — and it rebuilds along the bottom edge, where water pools and dries after every shower. Panels are wired in strings, so one soiled band drags the whole array down more than its share. That stubborn layer is what a proper clean is actually for, and it's the part that pays back.
When the honest answer is no
Candour first. If your array is steep, inland and rinsed by regular rain, cleaning it is largely money spent on tidiness. We'll say so. There's no film we'd be removing that the next storm wasn't going to handle for free. Same story if the panels are already clean — a scheduled wash buys nothing until the grime has had time to rebuild. 'Worth it' is a genuine question, and for some roofs the honest answer is no.
Cleaning can't fix everything, either. Glass that has clouded with age, cells that have degraded, a failing inverter or a wiring fault — none of it comes back with a soft brush and pure water. If your output has dropped and the panels already look clean, the problem is electrical, not dirt, and washing them is the wrong call. A clean recovers what soiling took. It doesn't reverse worn-out hardware, and we won't pretend it does.
Getting the number for your own roof
So the worth-it test is short. Are you near the water or a flight path, sitting on a low pitch, watching a film that survives the rain? Then a clean recovers real yield and pays back — and near the coast the film rebuilds fast enough that a quarterly cadence is the honest one, which is why solar sits inside the Schmick Plan as scheduled work. Flat, inland, rain-washed and already clean? Leave it, and spend the money on something that needs it.
Solar is quoted per job — pitch, access, panel count and how bonded the grime is all move the price — so there's no shelf figure to hand you. The instant quote settles it. Answer a few questions about the roof and it returns a firm, bookable price in about sixty seconds, and that price holds unless the place turns out materially different in person. Worth it or not, you'll know the real number before you decide — which beats guessing from a study written for someone else's roof.