What solar panel cleaning covers
Cleaning is the physical removal of soiling from the panel glass surface. A professional clean uses purified (deionised) water and a soft-bristle brush or water-fed pole to break down and rinse away particulate film, bird droppings, pollen, and biological growth.
A good cleaning service also includes a visual inspection of the panels from the ground — checking for obvious cracks, delamination, discolouration, loose frames, or debris accumulation — and will flag anything unusual to the homeowner. But the cleaner is not an electrician. They are assessing what they can see; they are not testing circuits, measuring cell performance, or diagnosing inverter faults.
Cleaning visits are typically booked annually or twice-yearly. The cost is £60–£150 for a domestic installation.
What solar panel maintenance covers
Maintenance is the inspection, testing, and servicing of the solar installation as an electrical system. A qualified solar engineer (MCS-certified) checks DC cable connections, inspects junction boxes, tests string voltages, reads inverter fault logs, verifies isolator function, and assesses panel condition at an electrical level — including thermal imaging to detect hotspots invisible to the naked eye.
A full maintenance visit may also include checking roof penetrations and mounting hardware for corrosion or movement, verifying export metering, and reviewing inverter firmware. Most solar engineers recommend a maintenance inspection every three to five years, or immediately if the system shows unexplained output loss or fault codes.
Maintenance costs significantly more than a clean — typically £150–£300 for a domestic inspection — and requires a qualified electrician or solar installation engineer, not a cleaning operative.
Where the overlap is
Some established cleaning businesses offer a combined service — clean plus basic condition report — that bridges the gap. This is useful but has limits: a cleaner reporting visible panel damage is not the same as an engineer testing cell performance. The two should be understood as complementary, not interchangeable.
For a new installation (under five years old, no fault codes, stable output), an annual clean plus a five-year maintenance check is a reasonable baseline. For an older system or one that has shown output anomalies, a maintenance inspection should precede or accompany the next clean.
Who to call and when
Book a cleaning service when: output is lower than expected and the panels are visibly dirty; it has been more than 12 months since the last clean; you can see bird droppings, moss, or pollen accumulation on the glass.
Book a solar maintenance engineer when: the inverter is displaying fault codes; output is low on clear days even after a recent clean; the system is more than five years old and has never had a professional inspection; you are buying a property with an existing solar installation; or the inverter is more than ten years old.
If you are unsure which applies, start with the cheaper option: a clean removes soiling as a variable. If output does not recover after the clean, an engineering inspection is the next step.