Professional vs DIY solar panel cleaning in Gauteng

The honest answer: what DIY can and cannot do

If your panels are on a single-storey roof with safe access, and all you do is rinse loose dust with a hose from the ground early in the morning, DIY is genuinely fine. It will lift some of the light surface dust and it costs you nothing.

What DIY does not do is remove the layers that actually cost you generation: pollen bonded by dew, veld-fire ash, road film, and bird droppings that have dried onto the glass. Those need physical contact with the right brush and the right water — which is where most DIY attempts either fail or cause damage.

Why tap water is a problem in Gauteng

Rand Water supply across most of Gauteng is moderately hard: it carries dissolved calcium and magnesium. When you hose a panel and let it dry in Highveld sun, the water evaporates and leaves those minerals behind as a white scale on the glass.

That scale is worse than the dust you set out to remove. It bonds to the anti-reflective coating, it does not rinse off next time, and over repeated cleans it builds into a permanent haze that scatters incoming light. Removing established scale needs a mild acid treatment and careful work — a far bigger job than the original clean.

This is the single most common way a well-intentioned DIY clean leaves a panel permanently worse off than before.

Household detergents, and why 'a bit of Sunlight' is not harmless

Dishwashing liquid, car shampoo and general-purpose cleaners all leave a surfactant residue. That residue is slightly sticky, so the panel attracts and holds dust faster after the clean than it did before — you get a few bright days and then a quicker decline.

Stronger products are worse. Ammonia-based glass cleaners, bleach, abrasive cream cleaners and solvent degreasers can attack the anti-reflective coating and, over time, the EVA encapsulant and frame seals. Damage to an AR coating is not repairable; the panel simply reflects away light it used to absorb.

Pressure washers, hot glass and cracked cells

A domestic pressure washer runs well above what panel manufacturers permit. Directed at the frame seal it drives water past the seal into the laminate, which shows up months later as delamination, moisture ingress or a failed panel — and the failure looks exactly like a warranty claim the manufacturer will decline.

The second hazard is thermal shock. A panel sitting in Highveld midday sun can be well over 60°C on the glass. Hitting it with cold municipal water can crack a cell or the glass outright. Every clean should happen early morning or late afternoon on cool glass, and this is the rule DIY attempts break most often because midday is when people have time.

The third is abrasion. Kitchen scourers, hard-bristled brooms, squeegee blades with grit trapped in them and even a dropped hose fitting will micro-scratch the coating. Those scratches are permanent and they accumulate.

The risk nobody prices in: the roof itself

Most South African solar arrays sit on tile or IBR sheeting at a pitch that is unforgiving when wet. Cleaning means water on the roof, which means the surface you are standing on is slippery for the whole job. Falls from residential roof height are a leading cause of serious domestic injury.

There is also the roof to think about. Standing in the wrong place on a concrete tile cracks it, and on older IBR or torch-on you can dent sheeting or damage waterproofing in ways that only show up in the first big storm. Walking on the panels themselves — which people do to reach the top row — causes micro-cracks in cells that no visual inspection will pick up but that a thermal camera will find later as hot spots.

Warranties: what you are actually risking

Panel manufacturers publish cleaning instructions, and most product warranties exclude damage caused by improper cleaning: pressure washing, abrasives, chemical cleaners and mechanical damage from foot traffic. Installer workmanship warranties commonly exclude damage caused by anyone other than a competent contractor working on the array.

In practice, that means a cracked panel or a delaminated laminate after a DIY clean is your cost, not the manufacturer's. The other half of it is documentation: if you ever do claim, an invoice from a qualified electrical contractor showing the array was cleaned and inspected properly is a strong piece of evidence. A garden hose leaves no record.

Insurance follows a similar logic. If a fire or water-ingress claim traces back to work done on the roof, the insurer will ask who did it.

What a professional clean adds beyond clean glass

RobCon Electrical cleans with a soft-brush method and no harsh chemicals, so the anti-reflective coating stays intact and no residue is left to attract dust. Work is done on cool glass, with proper working-at-height equipment, and the array stays generating throughout.

The part that matters most is that we are a qualified electrical contractor, not a cleaning company. While we are on the roof we are checking things a hose never will: loose or chafing DC cabling, corroded or arcing MC4 connectors, cracked or delaminating panels, visible hot spots, loose mounting hardware, and debris or blocked drainage under the array. A live DC array with a degrading connector is a genuine fire risk, and it is found by someone who knows what to look for.

Residential cleaning starts at R35 per panel and commercial at R25 per panel, excluding VAT, with a minimum call-out. A typical 10 to 20 panel home takes one to two hours.

Does the maths favour DIY?

Cleaning 16 panels professionally costs R560 excluding VAT. An 8 kWp system carrying a 15% soiling loss is giving away roughly R480 a month at typical Gauteng tariffs, so the clean pays back in well under two months.

Against that, a single cracked panel is R2,500 to R5,000 supplied and fitted, a scale-hazed array is a permanent generation penalty, and a fall is in a different category altogether. DIY saves a few hundred rand and carries a low-probability, high-cost downside. That is the whole trade-off in one sentence.

If you are going to DIY anyway, do it this way

Stay on the ground and use an extendable water-fed pole with a soft brush head rather than climbing. Work early morning or late afternoon on cool glass, never at midday. Use the softest brush you can find and no detergent of any kind.

Never use a pressure washer, never use abrasive pads or scourers, never walk on the panels, and never work alone on a roof. Dry-brushing a dusty panel is also a mistake — dry grit dragged across glass is sandpaper. And if you have a double-storey home, a steep pitch, bird-proofing mesh, or any panel you cannot reach safely from the ground, that is the point to stop and call someone.

Common questions

Can I clean solar panels with just water?

Clean water is the safest thing to use, but Gauteng's tap water is hard enough to leave mineral scale on the glass when it dries in the sun. That scale builds up over repeated cleans into a permanent haze. Rinsing loose dust from the ground occasionally is fine; regular cleaning is better done properly.

Can I use dishwashing liquid or soap on solar panels?

No. Detergents leave a surfactant film that makes panels attract dust faster after the clean, and stronger cleaners containing ammonia, bleach or solvents can permanently damage the anti-reflective coating. Professional soft-brush cleaning uses no harsh chemicals for exactly this reason.

Can I use a pressure washer on solar panels?

Never. Domestic pressure washers exceed the pressure panel manufacturers allow and can force water past the frame seal into the laminate, causing delamination and moisture ingress months later. It is also one of the fastest ways to void a panel warranty.

Will cleaning my own solar panels void the warranty?

It can. Most manufacturer warranties exclude damage from improper cleaning — pressure washing, abrasives, chemical cleaners and foot traffic on the array — and installer workmanship warranties often exclude work done by anyone who is not a competent contractor. Keeping an invoice from a qualified electrical contractor protects you if you ever claim.

What time of day is safe to clean solar panels?

Early morning or late afternoon, while the glass is cool. Cold water on panels that have been sitting in Highveld midday sun can crack a cell or the glass through thermal shock.

Is it worth paying for professional solar panel cleaning?

For most Gauteng systems, yes. At R35 per panel residential, a typical clean pays for itself in recovered generation within about two months, and the visit includes an electrical inspection of the array — cabling, connectors, hot spots and mounting — that a DIY clean cannot give you.

Keep reading

• How often should you clean solar panels in Gauteng?
• How much output do dirty solar panels really lose?
• Commercial solar panel cleaning: a facility manager's checklist