How to Clean Solar Panels on a Roof
Reaching a roof-mounted array safely, and why the professional answer is almost always to stay on the ground.
Almost every residential array in South Africa is roof-mounted, which turns a simple cleaning job into an access problem. The panels are four to eight metres up, on a pitched surface, and the one thing you must not do is stand on them.
This page is about the access side specifically — how to reach a roof-mounted array safely, and why the professional answer is almost always to stay on the ground.
The rule: never walk on the array
Panel glass is engineered for evenly distributed load — hail, wind, the weight of snow. It is not designed for a person standing on one point of it. What happens is microcracking in the cells beneath the glass: invisible from above, permanent, and it shows up weeks later as reduced output from one string.
It will also void the panel warranty in most cases. Manufacturers are explicit about it.
The same goes for the roof sheeting between panels. Standing on a tile roof cracks tiles; standing on IBR or corrugated sheeting between purlins deforms it and creates leak paths. Even where the roof takes your weight, you’re working on a pitch, on a wet surface, with water running under your feet.
Clean from the ground instead
The professional method for roof-mounted arrays is a water-fed pole operated from ground level. A telescopic pole with a soft brush head and water jets, fed with purified water, lets you reach across a roof-mounted array without ever leaving the lawn.
The reach you need depends on the building:
| Building | Approximate reach needed | Pole |
|---|---|---|
| Single-storey, low pitch | 4–6 m | 4 m or 6 m aluminium |
| Single-storey, steep pitch or wide array | 6–7 m | 6 m fibreglass |
| Double-storey | 8–9 m | 9 m fibreglass |
Remember you’re reaching diagonally, not straight up. A 6m pole does not clean a panel 6m above you — it reaches roughly 6m along its own length, so on a pitched roof the useful vertical reach is less. Size up rather than down.
Aluminium is cheaper and stiffer at shorter lengths. Fibreglass is lighter for its length, which matters a great deal at 9m when you’re holding it extended for an hour. Above about 6m, the weight in your hands is the limiting factor, not the reach.
Why purified water matters even more on a roof
When you clean from the ground you cannot dry the panels afterwards — you have no way to reach them with a cloth. That makes water quality non-negotiable rather than merely preferable.
Purified water dries spot-free with no intervention. Tap water dries into a mineral film that you now have no way to remove without going up. This is the mechanism behind most “I cleaned my panels and they look worse” complaints.
Check your tap water with a TDS meter before you start. Under about 10 ppm at the brush head dries clear. Anything much above that will spot. Our pure water setup guide covers how to get there and what it costs.
When you can’t reach from the ground
Some arrays genuinely can’t be reached from below — a double-storey with an array set well back from the eaves, a flat roof with a parapet, panels behind a courtyard wall.
In that case, work from the roof but not on the array:
- Access the roof properly — a correctly footed ladder at the right angle, tied off at the top, extending at least a metre above the roof line.
- Stay on the roof structure, on the purlins or over rafters, never on the panels or between them on unsupported sheeting.
- Work from the edge of the array inward with a shorter pole, so you’re reaching across rather than standing among the panels.
- On anything steep, high or wet — use a harness and an anchor, or don’t do it.
- A wet roof is a different surface to a dry one. Water running off an array makes the sheeting below it genuinely dangerous.
If you’re cleaning as a business, the honest position is that a longer pole is cheaper than an injury and far cheaper than a claim. The reason professionals invest in 9m poles is not convenience.
Getting water to the roof line
Cleaning at height from the ground has one practical constraint people underestimate: you need pressurised water at the brush head, and gravity won’t provide it.
A pole running at roughly 1.5 litres a minute will get through 50–100 litres on a typical residential array of 12 to 20 panels. That water has to be purified, and it has to arrive with enough pressure to reach the top of an extended pole.
For a fixed base within hose reach, a pump drawing from a storage tank works. Where you can’t run hose — complexes, estates, anywhere you can’t park close — a 15 litre mobile water-fed pole pump carries and pressurises its own supply, topped up from 25 litre containers as you work.
Order of work on a roof-mounted array
- Look at the array from the ground first. Note the pitch, how far back the panels sit from the eaves, and whether anything is obviously damaged or loose.
- Go early. Panels must be cool. Cold water on hot glass risks thermal shock, and on a roof you also want to avoid working on hot sheeting.
- Clear debris from below the array. Leaves and nests build up under panels and hold moisture against the roof.
- Wet the panels and let it soak before you brush, so you’re not dragging dry grit across the coating.
- Work top row down so runoff doesn’t re-dirty finished panels.
- Rinse with pure water and leave it. No drying.
- Check the inverter the next clear day and compare.
Frequently asked questions
Can I walk on my solar panels to clean them?
No. Panel glass isn’t rated for point loading and the microcracking it causes is invisible, permanent and usually voids the warranty.
What length pole do I need for a roof array?
Around 6m for a single-storey house, 9m for a double-storey. Because you reach diagonally across a pitched roof rather than straight up, size up if you’re between two options.
Can I clean roof panels with a hose from the ground?
No, not properly. A hose will knock loose dust off, but it won’t reach the far side of an array, it won’t shift bonded grime, and hard tap water will leave mineral spots that you can’t then reach to remove.
Is it safe to clean panels in the rain?
Not usually. Rain is a good time in one sense — the panels are cool and already wet. But wet roofs and wet ladders are the main cause of serious falls. Clean from the ground if it’s wet, or wait.
Do I need to switch the system off first?
Usually not. For an exterior clean with a pole you’re not touching electrical components, so it’s not usually necessary. If you’re going onto the roof and working close to cabling, junction boxes or a damaged panel, isolate the array first and treat any damaged panel as live.