What DIY cleaning can achieve
Rinsing panels with a garden hose from ground level removes loose dust, pollen, and light soiling. After a particularly dusty summer or a dry spell, this can recover a few percentage points of output at no cost and with minimal risk.
If your panels are single-storey, easily accessible, and in generally good condition, a gentle rinse every couple of months between professional cleans is a reasonable supplementary measure.
What DIY cleaning cannot achieve
A hosepipe does not remove bonded deposits — the mineral scale, traffic film, and biological growth (moss, lichen, algae) that accumulate over months and are responsible for most efficiency losses. These require purified (deionised) water and a soft-bristle brush to break down.
Tap water, even from a hose, leaves calcium and mineral deposits as it evaporates. On a dry day, hosing your panels can actually make the soiling slightly worse than before. Purified water — produced by passing tap water through a reverse osmosis or deionisation filter — evaporates completely without leaving residue. This equipment costs £300–£1,000 and is not practical for a one-off home use.
Safety risks to consider
The majority of UK domestic solar installations are on pitched roofs at heights of 4–8 metres. Working at height is the leading cause of fatal workplace accidents in the UK, and the risks are the same for homeowners on ladders. Even single-storey panels require careful ladder positioning, secure footing, and ideally a second person present.
Wet surfaces, the weight of a bucket or pole system, and the instability of reaching sideways on a ladder all increase fall risk significantly. Most professional solar cleaners use water-fed pole systems that allow them to clean from the ground, eliminating this risk entirely.
Warranty implications
Many solar panel manufacturers specify in their warranty documentation that cleaning must be carried out using approved methods — typically purified water and non-abrasive equipment — to remain valid. Using washing-up liquid, household cleaning products, or abrasive materials voids the warranty on most major panel brands.
Some installers go further and require a qualified operative for any maintenance activities. Check your installation documentation before cleaning, and keep a record of any professional cleans carried out.
When to call a professional
Any installation on a first floor or above should be cleaned professionally. The output recovery justifies the cost and the safety case is clear.
If you can see bird droppings, moss, or lichen on the panels, a hose will not remove these effectively. A professional clean is the right tool.
If your inverter monitoring shows a consistent output drop over several months that cannot be explained by weather, a professional clean and inspection is the fastest way to diagnose whether soiling or a fault is responsible.