Solar panel cleaning glossary
Plain-English explanations of the terms you will come across.
- Anti-reflective coating
- A thin layer on the front glass of most solar panels that reduces reflection so more light reaches the cells. Abrasive pads, blades and high pressure can wear or scratch it.
- Bird proofing mesh
- Galvanised or PVC-coated wire mesh fixed around the edge of a rooftop array, usually with non-drill clips, to stop pigeons and other birds getting into the gap under the panels.
- Bypass diode
- A component inside a panel's junction box that lets current flow around a shaded or damaged group of cells, limiting the output loss and reducing the risk of overheating.
- Deionisation (DI)
- A final filtering stage using resin that removes remaining minerals from water after reverse osmosis, bringing it close to zero dissolved solids so it dries on glass without leaving marks.
- Hot spot
- An area of a solar panel that runs much hotter than the rest, often from a damaged cell, poor connection or persistent shading. It can cause browning or burn marks and is confirmed by thermal imaging.
- Inverter
- The unit that converts the direct current produced by the panels into alternating current used in the home. Its display or app usually shows generation and any fault codes.
- kWp
- Kilowatt peak, the rated maximum output of a solar system under standard test conditions. A typical UK home system is often around 3 to 5 kWp, depending on the number and size of panels.
- MCS
- The Microgeneration Certification Scheme, which certifies installers and products for small-scale renewable systems in the UK. MCS certification is often needed for export payments under the Smart Export Guarantee.
- Microinverter
- A small inverter fitted to each individual panel, converting its output separately. Like optimisers, microinverters reduce the knock-on effect of one shaded or soiled panel.
- Optimiser
- A small electronic device fitted behind each panel that lets it work independently of the others, so shading or soiling on one panel has less effect on the rest of the string.
- Reverse osmosis (RO)
- A filtration process that forces water through a fine membrane to remove most dissolved minerals and impurities. It is the first stage in producing the purified water used to clean solar panels spot-free.
- Soiling loss
- The drop in a solar panel's output caused by dirt, dust, droppings, lichen or other material on the glass. It can be small for light dust and much larger for opaque fouling.
- String
- A group of solar panels wired together in series to an inverter. On a string system, shading or soiling on one panel can reduce the output of the other panels in the same string.
- TDS
- Total dissolved solids, the amount of minerals in water measured in parts per million. Cleaners use a TDS meter to check their water reads zero or very close to it before cleaning panels.
- Water-fed pole
- A lightweight telescopic pole, usually carbon fibre, that carries purified water up to a soft brush at the top, letting cleaners wash panels on two and three-storey roofs from the ground.
Last updated 6 November 2026