Dirty solar panels could be costing households £150 a year
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Research reveals when cleaning solar panels could pay for itself, which homes face the greatest risk and why an annual clean may be an unnecessary expense
Solar panel owners could be losing as much as £150 a year by failing to keep them clean, research has shown.
As the nation prepares for plug-in solar panels to hit UK shops for the first time on August 27, a specialist solar company has crunched the numbers to work out what sort of impact dirt on solar panels can have.
According to Recharge Renewable, bird mess, leaves, dust and lichen can block an alarming proportion of the available sunlight, with a standard 4kW home system losing as much as 10% of its efficiency.
Basing the cost of this loss on the July 2026 Ofgem price cap unit rate of 26.11p per kWh, the company has worked out that dirt wastes almost £100 of electricity a year, rising to around £150 where soiling is heavy.
In larger systems the losses can be greater, with a 6kW solar array losing up to £200 if the panels are dirty.
Households with panels that sit below trees, are in areas that attract regular bird activity, lie at a shallow angle where rain runs off poorly, or face agricultural and construction dust are at the highest risk of dirt settling.
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Leaves trapped along the lower edge and patches of lichen are another two of the biggest culprits because they create permanent shading that rain never shifts.
A spokesman for Recharge Renewable said: "Visible build-up and a lasting performance drop should point in the same direction before owners pay for cleaning.
"If output falls suddenly or one section stops producing, contact the installer because dirt may not be the cause."
To clean panels safely and effectively, the best option is to call in a professional service, especially if they are on the roof.
For panels reachable from the ground, such as those on a single storey extension or garage, use a soft brush on a telescopic pole with plain water or a small amount of mild washing up liquid.
Rinse thoroughly with clean water so no soapy residue dries on the glass. Clean early in the morning or in the evening when the panels are cool, because cold water hitting hot glass risks cracking it and warm panels dry too fast, leaving streaks and mineral spots.
Avoid pressure washers, abrasive pads, harsh chemicals and metal tools. All of them can damage the glass coating or the seals around the frame, and that kind of damage can void the warranty.
A typical domestic clean costs £4 to £15 per panel, or around £80 to £150 for a whole system, so households should weigh the quote against the likely saving.
A grimy array in a high risk spot pays the cleaning bill back within a year or two, while a clean-looking system in a rainy area can be left alone.
Energy Saving Trust guidance confirms panels need little maintenance and rain clears loose dust naturally, so a fixed cleaning schedule wastes money for many homes.
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