How to clean solar panels without damaging them

Why cleaning requires the right method

A solar module is covered with toughened glass, often with a surface coating. Although designed to withstand hail, this glass can still be scratched or damaged by sudden changes in temperature.

Poor cleaning can leave micro-scratches, damage seals or frames, and put your warranty at risk. First read the panel manufacturer's instructions: any rules on water, brushes and cleaning products take priority over this general guide.

Start with safety

Roof work carries a risk of falls, especially on wet surfaces. Work from the ground with a telescopic pole where possible. If roof access is unavoidable, use suitable fall protection and do not work alone.

• Never stand or lean on panels: cells can develop damage you cannot see.
• Do not touch cables or connectors, and never clean a panel with cracked glass.
• If access is uncertain, hire an appropriately equipped professional.

Choose the right time

Clean early in the morning, late in the afternoon or under cloud cover, while the panels are cool. Cold water on hot glass can cause thermal shock, and water evaporating quickly may leave limescale marks. Avoid freezing conditions too.

A gentle cleaning method

1. Inspect the panels from the ground. Report any cracked panel to your installer rather than cleaning it.
2. Pre-rinse with low-pressure water to soften dust and bird droppings before brushing.
3. Move a soft-fibre brush over the glass without forcing it, working from top to bottom.
4. Rinse away loosened dirt. If marks remain, make another gentle pass instead of pressing harder.
5. Allow the panels to air dry. If your water is very hard, consider purified water to reduce white marks.

Which equipment is suitable?

Soft, dense PBT fibres are designed for photovoltaic glass. Our telescopic brush (from CHF 299) includes a water supply. For larger roofs, there is a motorised double-disc brush (from CHF 1,390); the remote-controlled cleaning robot (CHF 9,979) is intended for very large surfaces and is also available to rent.

Water alone is normally enough with these brushes. Always check the panel manufacturer's care instructions first.

Avoid these mistakes

• Do not use a pressure washer: it can damage seals, frames or the glass surface.
• Avoid abrasive pads, metal scrapers, aggressive chemicals and hard brushes.
• Do not wash hot panels in direct sunshine or clean on freezing days.
• Never walk on the panels, even if the glass looks strong.

Key points at a glance

• Safety first: work from the ground where possible; otherwise use suitable fall protection or hire a professional.
• Clean cool panels in the early morning, late afternoon or under cloud cover.
• Use low-pressure water and a soft-fibre brush, without aggressive chemicals.
• Never use pressure washers or hard tools, or stand on the modules.

Unsure which equipment to choose, or prefer someone else to do the work? Ask us for a free quote; we reply within 24 hours.

Look after your brush

Rinse the brush after each use and let it dry in the shade with its fibres facing down. Sand trapped in the fibres can scratch glass. Inspect worn heads and discs, and drain hoses before winter.