How to clean solar panels on your roof safely

To clean solar panels, switch the system off following your installer's instructions, wait for a cool part of the day, then wash the glass gently from the ground with plain water and a soft brush on an extendable pole. Never use a pressure washer, harsh chemicals or anything abrasive, and never climb onto the roof or stand on the panels.

Here is how to do it step by step, what to avoid, and when it is safer to leave it to someone with the right kit.

Do I need to turn off solar panels to clean them?

Most UK solar guides and installers say yes. Panels produce electricity whenever light hits them, and you are putting water near an electrical system, so switching off before you start is the safe habit. Follow the shutdown steps in your installer's handover pack or the inverter manual, because the switches and their order vary from one system to the next.

Switching off is not a fix for damage. If you can see cracked glass, loose cables or scorch marks, do not clean the panels. Keep water away and call your installer.

What you need

• A soft brush on an extendable pole, made for glass, not a stiff deck brush
• Plain water, ideally pure deionised water so it dries without spots
• A hose on a gentle setting or a bucket for rinsing
• Something to stand on that is safe and level, if you need a little extra reach from the ground

Step by step

1. Switch the system off following your installer's instructions.
2. Pick a cool time. Early morning, evening or an overcast day is best. Panels get very hot in the sun, and cold water on hot glass adds thermal stress.
3. Rinse first to soften dirt and wash off loose dust.
4. Brush gently from the top of each panel down, so dirty water runs off rather than across clean glass.
5. Work on bird droppings with water and patience. Let them soak and brush again rather than scraping.
6. Clean the bottom edge of each panel carefully, because that is where the grime line builds up.
7. Rinse off and let the panels dry, then switch the system back on in the order your manual gives.

What never to use on solar panels

• Pressure washers. High pressure can force water past the panel seals.
• Detergents, washing up liquid or strong cleaners. They can leave a film that attracts dirt and can affect seals and the anti-reflective coating.
• Abrasive pads, scrapers or metal tools, which scratch the glass.
• Your feet. Standing on a panel flexes the glass and can crack the cells underneath without it showing.

If your panel maker's manual recommends a particular mild cleaner, follow it. Otherwise plain water is the safe choice.

Cleaning panels on the roof

Ground-mounted panels and low single-storey roofs are fine to do yourself with a pole. Panels on a two-storey pitched roof are different. A ladder against the gutter does not get you safely onto the roof, and working at height without the right equipment and training is how people get seriously hurt. Stay on the ground.

This is where professional kit earns its keep. A water-fed pole system pumps deionised water up a long carbon pole to a soft brush, so the whole array can be cleaned from the garden. The water has the minerals removed, so it dries clear without leaving spots or residue.

When to call a professional

• Your panels are on a two-storey roof or higher
• There is heavy lichen, moss or baked-on bird mess that water alone will not shift
• You want a record of the clean for your warranty or maintenance plan
• You would like the panels checked for damage, lifted panels or loose clips at the same time

Solar panel cleaning around Bristol and Bath

We clean panels from the ground with deionised water and soft brushes, check the frames and clips while we work, and give you a record of the clean. See our solar panel cleaning service or find your area: Bristol, Bath or Keynsham. If you are not sure your panels need doing yet, read do solar panels need cleaning. Call Tom on 0117 279 0045 for a free quote.