When should you clean solar panels in Switzerland?

There is no fixed schedule

Location matters more than a fixed date. A city roof, farm building or roadside installation faces different levels of dust and deposits. Inspect panels regularly from a safe position and compare their visible condition with your monitoring data. A change in output can have causes other than dirt.

Signs that cleaning may be needed

Rather than following a fixed date, look for deposits: a grey or yellow haze visible from the ground, bird droppings that remain after rain, dirt along the lower panel edge, or moss and lichen at the frame. Compare your output with similar weather in previous periods; lower output can have other causes too.

Bird droppings can shade part of a cell even when the marks are small. If you can reach them safely, remove them promptly with water and a soft brush.

Spring: pollen and rain

Pollen can settle across the glass. Rain may remove some deposits, but stubborn patches and bird droppings may need gentle washing. Wait until flowering has passed if the panels will immediately become coated again.

Summer: dust and heat

Dry spells, agricultural activity and nearby roads may leave dust on panels. Never wash sun-heated modules with cold water. Choose a cool morning or overcast period and use low-pressure water.

Autumn: leaves and preparation

Remove leaves only if access is safe. Check drainage and panel edges before winter. A gentle clean can make sense where dirt has accumulated; do not climb on an unsafe roof.

Winter: frost and snow

Do not scrape panels with hard tools or pour hot water on icy glass. Roofs are slippery and snow removal can cause damage. Ask a specialist when an intervention is genuinely necessary.

The calendar at a glance

• Spring: after flowering, remove pollen and winter deposits.
• Summer: after harvesting in agricultural areas; clean only early in the morning.
• Autumn: clear leaves and debris before winter, if access is safe.
• Winter: do not wash in frost; allow snow to melt naturally.

At any time of year, keep panels cool, use low-pressure water and a soft brush, and put safety first.

Decide based on the site

• Look from a safe position and record visible deposits.
• Follow your panel manufacturer's cleaning instructions.
• Avoid hot glass, frost and dangerous roof access.
• If in doubt, ask for an assessment rather than assuming every panel needs washing.