How to Clean Solar Panels Safely (and When Not To)

Clean solar panels early in the morning or after sunset, with a soft brush on a telescopic pole and purified or deionised water, never tap water, never detergent, never a pressure washer. If the panels are on a roof, do not climb up for it. Ground-reachable panels are a sensible job to do yourself; roof panels are not, and the reasons are below.

Perth panels get dirtier than most. Summer easterlies carry dust from the hills, the Fremantle Doctor brings salt in from the coast, bore-water sprinklers leave orange and white mineral spots on anything they reach, and birds treat a warm north-facing array as a perch. Rain does not fix it, it moves the grime around and dries to a film. A dirty array in Perth can lose somewhere between 5 and 25 per cent of its output depending on how long it has been left, so the question is worth asking properly.

What do you clean solar panels with?

Three things, and nothing else.

• A soft-bristle brush or a microfibre sleeve on a telescopic pole. The glass on a solar panel carries an anti-reflective coating that scratches more easily than a window, so nothing abrasive, no scourers, no stiff brooms.
• Purified water. Deionised or demineralised water from a hardware store is the practical option at home, or a water-fed pole with a filter if you own one. Perth scheme water and especially bore water carry dissolved minerals that dry as spots, which is the same reason a tap-washed car looks worse than before you started. Purified water has nothing in it to leave behind, so the panel dries clean.
• Early morning or evening light. A hot panel flashes water dry before you can rinse it, and cold water on hot glass is a thermal shock the glass does not need.

What not to use: detergent or dishwashing liquid (leaves a film that attracts dust and can void some manufacturer warranties), vinegar or any acid (attacks the anti-reflective coating and the aluminium frame seals), a pressure washer (forces water past the edge seals and into the cells), and anything abrasive.

How to clean solar panels on the ground, step by step

This is for panels you can reach with both feet on the ground, such as a shed array, a ground mount or a low pergola.

1. Switch the system off at the inverter and the solar supply main switch, in that order, following the shutdown procedure on the label. Water and a live DC string are not a combination to improvise with.

2. Hose off loose dust and leaves with a gentle flow first. Most of the dirt comes off at this stage.

3. Wet the brush with purified water and work from the top edge downward in overlapping strokes, so the dirty water runs off the bottom edge rather than back over clean glass.

4. Rinse with purified water, again top to bottom.

5. Leave it to dry on its own. Do not squeegee a panel, the blade edge catches on the frame lip and the coating.

6. Switch the system back on in the reverse order. Check the inverter display a day later; on a dirty array the output lift is visible.

Allow 10 to 15 minutes a panel the first time, far less once you know the routine.

When should you not clean solar panels yourself?

When they are on a roof, which in Perth is nearly always. The reasons are not about skill, they are about where you are standing.

• Falls from ladders and roofs are among the most common causes of serious injury around Australian homes, and a wet, sloping, dust-covered roof with a brush in one hand is the worst version of that. Nothing a clean panel saves on a power bill covers a fall.
• Walking on a tin roof dents it and loosens screws, and walking on tiles cracks them. A cracked tile is a leak you find in June.
• Panel warranties and installer warranties commonly exclude damage from improper cleaning. Detergent, pressure washing and standing on panels are the usual exclusions, and the installer will ask.
• Bore-water staining on panels does not come off with a hose, and scrubbing it harder is how coatings get damaged.

A professional solar panel clean reaches roof panels from the ground with a water-fed pole and purified water, up to six storeys, so nobody is on your roof and no ladder is against your gutter. Coates charges $7 to $10 a panel for most Perth homes, so a 20-panel system is $140 to $200, which is less than most households lose in output over a year when the array is left dirty. Details are on our solar panel cleaning in Perth page.

How often should solar panels be cleaned in Perth?

Once a year is the baseline for a suburban Perth roof, and twice a year if the array faces a bore sprinkler, sits under trees, or is near a bird roost. The best single time is late winter to early spring, August or September, so the glass is clean going into the high-yield months when a dirty panel costs the most. A second clean after summer catches the dust season.

The signs it is overdue are visible from the ground: a pale haze across the glass, white or orange spotting in a pattern that matches your sprinklers, dark streaks beneath where birds sit, or an inverter reading that has drifted down with no change in weather.

Does rain clean solar panels?

No. Rain wets the dust and moves it to the lower edge of the panel, where it dries into a stripe that shades the bottom row of cells. On a panel, shade on one cell drags down the whole string, so that stripe costs more than its size suggests. Rain also does nothing to bird droppings, pollen or bore-water minerals. Panels in Perth look cleanest in winter because they are wet, not because they are clean.

Can you clean solar panels with a hose from the ground?

A gentle hose rinse from the ground is harmless and takes off loose dust, so there is no reason not to do it after a dust storm. It will not remove the film that reduces output, and if you are on scheme or bore water it leaves spots as it dries. Treat it as a tidy-up between cleans, not a clean.

What about commercial and strata arrays?

Large arrays on warehouses, schools and apartment buildings are quoted per site, with volume rates over 100 panels, and are cleaned on a schedule with SWMS and public liability certificates supplied before work starts. See commercial solar panel cleaning in Perth.

Frequently asked questions

Can I clean my solar panels myself?

Yes, if they are reachable from the ground, using the method above. If they are on a roof, the safe answer is no, and a professional clean at $7 to $10 a panel is the cheaper option once a fall or a cracked tile is on the other side of the ledger.

What is the best time of day to clean solar panels?

Early morning or after sunset, when the glass is cool and the water will not flash dry. Midday on a Perth summer roof is the worst possible time for the glass and for the person.

Will dishwashing liquid damage solar panels?

It can leave a residue that attracts dust and it is a common warranty exclusion. Use purified water only.

Do I need to switch the system off to clean the panels?

Yes. Follow the shutdown procedure on the inverter label, inverter first then the solar supply main switch, and reverse it afterwards.

How much output do dirty panels lose in Perth?

Anywhere from about 5 per cent on a lightly dusty array to 25 per cent or more where bird droppings or bore spotting shade individual cells. The inverter display before and after a clean is the most honest measure for your own roof.

Do you clean panels on two-storey homes?

Yes. Water-fed poles reach up to six storeys from the ground, so a two-storey roof in Dianella or South Perth is routine.