Solar panels are a significant investment for any home or business. Most owners monitor their output carefully — but many overlook one of the simplest and most cost-effective ways to improve it: keeping the panels clean.
Do dirty panels actually lose efficiency?
Yes, measurably so. Research from institutions including NASA and multiple European energy bodies has found that soiling — dust, bird droppings, algae, and general atmospheric deposits — can reduce panel output by between 15% and 25% in typical conditions. Individual panels heavily soiled by bird droppings can lose significantly more.
In Norfolk, agricultural dust, pollen, and proximity to the coast (for some areas) all contribute to panel soiling. Properties near farmland or under flight paths for birds are particularly affected.
What counts as "dirty" for a solar panel?
Even a thin, barely visible film of dust reduces output meaningfully. Solar panels work by converting light to electricity, and anything between the sun and the photovoltaic cells reduces the light that reaches them. Visible grime is worse, but the effect begins long before dirt is obvious.
Why pure water cleaning is essential
Tap water must never be used on solar panels. The mineral residue left when tap water dries creates a film on the glass that reduces transmission and bonds future soiling more firmly. Pure water — filtered to remove all dissolved minerals — is the only appropriate cleaning solution for solar panel glass.
Is cleaning required for the warranty?
Many panel manufacturers specify regular professional cleaning in their warranty terms. Using appropriate methods (pure water, soft brushes, no abrasives) is typically a warranty requirement. Check your documentation — some policies specifically exclude damage from neglected maintenance.
How often should panels be cleaned?
Once or twice a year is typical for most UK installations. We recommend a clean in early spring (to clear winter accumulation before peak summer generation) and optionally in autumn.
The payback calculation is straightforward: if cleaning restores 15% of your output and costs less than 15% of your annual generation value, it pays for itself.