Do Solar Panels Need Cleaning? How to Tell When It's Worth It

Do panels clean themselves?

Mostly. Panels on a pitched roof shed dust and light dirt each time it rains. Flatter panels hold more dirt, because water runs off slowly. In most suburbs, rain keeps panels close to their best output for much of the year.

When does dirt actually matter?

• Bird droppings. They sit in one spot and act like shade.
• Coastal salt. Homes near the ocean can get a salty film after onshore winds.
• Dust and pollen. Near unsealed roads, farms, building sites and busy roads.
• Leaves and lichen. Under trees, debris collects along the bottom edge of panels.
• Long dry spells. A summer without rain lets dust build up.

How can I tell from my output?

Compare clear days in your inverter app over a few weeks. A slow, steady decline across clear days, with no new shade, is a sign of dirt. Seasonal changes are normal, so compare like with like: clear days in the same month.

How should panels be cleaned?

• Use clean water, ideally low-pressure, with a soft brush on an extension pole from the ground.
• Clean early in the morning or late in the day, when panels are cool.
• Avoid detergents, abrasive pads and pressure washers unless the panel maker allows them.
• Never walk on panels or climb onto the roof yourself. Hire a professional with fall protection for anything you can't reach from the ground.

Is professional cleaning worth paying for?

If output has clearly dropped and you can't safely reach the panels, yes. Otherwise, rain and an occasional check usually do the job.

A real example

We installed 9.5 kW of Risen panels with a 24 kWh GoodWe battery in Somerton Park, a beachside suburb in Adelaide. Homes near the water are the ones most likely to see a salty film after windy weather, so it pays for owners there to keep an eye on clear-day output.

The bottom line

Watch your output, not the calendar. Clean when the numbers or your eyes tell you to, and do it safely.