Can you pressure wash solar panels? No — do this instead
No. Don't pressure wash solar panels. The jet cracks the cells and strips the anti-reflective coating, and most manufacturers void the warranty if you do. The correct method is a soft brush with deionised water. Cleaning still matters, though — NREL research puts typical soiling loss around 5% of annual output, and up to 25% in the dirtiest locations.
The pressure kills the panel three ways
A pressure washer runs at thousands of PSI. A solar panel is a thin silicon wafer under tempered glass, sealed against the weather at its edges. Aim a jet at it and you do three kinds of damage at once. The first is microcracks — hairline fractures in the cells that you cannot see from the ground, but that quietly cut the panel's output for the rest of its working life. Once a cell cracks, there is no repair. You replace the whole panel.
The second casualty is the anti-reflective coating. Panels carry a microscopically thin layer that helps the glass drink in light rather than bounce it away. High pressure and abrasive tips scour that layer off, so the panel reflects more and generates less — the exact opposite of why you cleaned it. The third is your paperwork. Most manufacturers specify gentle washing only, and pressure cleaning voids the performance warranty. So you gamble a fifteen-year guarantee to save twenty minutes with a hose. The maths never works.
Soft brush, deionised water, nothing else
The method the manufacturers actually endorse is dull, and that is the point. A soft brush or microfibre pad, a steady flow of deionised water, and a light touch. Deionised water has had its minerals stripped out, so it lifts grime and then dries without leaving the chalky spotting that ordinary tap water leaves behind. No detergent that can smear or etch. No abrasive tip. No ladder leaned against the array. The panels come clean and the glass, the coating and the cells all survive the wash intact.
Timing matters as much as tools. Wash the panels early, while the glass is still cool — cold water hitting hot glass is its own way to crack a cell. Work from a roof-safe position or with a fed-pole from the ground, and never stand on the modules, because your weight flexes the wafer underneath. It is slow, unglamorous work with no spray-and-walk-away moment. That restraint is the whole method. The panel you don't blast is the panel still making power in ten years.
Dirty glass is a real tax on your output
None of this means dirt is harmless. Panels are self-cleaning in theory — rain rinses them — but Sydney's rain is inconsistent, and a film of dust, pollen, salt and bird mess builds up between the good downpours. NREL's photovoltaic soiling research puts the typical annual loss from that film at around 5% of output, and up to 25% in the dirtiest locations. Five per cent sounds trivial until you map it onto a system you paid five figures for and a feed-in tariff you were counting on.
The reason cleaning pays is compounding. A dirty panel does not fail loudly; it just underperforms, quietly, every sunny day, and the loss never shows up as a fault on your inverter app. Homes near the water get more of it — salt haze on the North Shore and around Middle Harbour settles on the glass and holds dust in place. So the answer to the headline question is a split decision: yes, clean them; no, never with pressure. The how is the whole story.
What a clean can't fix
Honest caveat: cleaning is not a cure-all. If your output has dropped and the glass is already clean, the problem is not soiling — it is more likely a failing panel, a tripped optimiser, an inverter fault, or shading from a tree that has grown since install. Washing those panels changes nothing, and anyone who tells you a clean will fix a wiring fault is selling you a wash you don't need. A soiling loss disappears the day you clean it. A hardware fault does not.
There is also a point of diminishing returns. In a wet Sydney winter, rain does a fair share of the rinsing on its own, and a spotless-but-shaded array in July will not repay a clean the way a dusty one in a dry February would. Good exterior care is knowing which is which. We would rather tell you the panels can wait than book a job that barely moves your meter. That candour is the brand — and it is cheaper for you.
Get the number before anyone gets the ladder
When the panels are genuinely due, the sensible move is to fold them into a visit that is already happening. Solar sits in the quote-per-job category — the price depends on pitch, access, array size and how filthy the glass has got — so there is no flat sticker. But the Schmick instant quote returns a firm, bookable price in about sixty seconds, and it holds unless the roof turns out to be materially different from what you described at the door.
Bundle the solar clean with the gutters or a house soft wash on the same visit and you save five to fifteen per cent, because the truck and the setup are already there. Or put the whole exterior on a Schmick Plan and the panels get washed on a schedule instead of whenever you next happen to remember. Either way the rule holds: soft brush, deionised water, no pressure — and a number you can see before anyone climbs a ladder.