Does cleaning solar panels make a difference? Yes, when the panels are actually dirty. Bird droppings, lichen and a build-up of grime block light from reaching the cells, and rain alone will not remove them. On a steep roof with clean-looking panels, though, the gain can be small, so it is worth checking before you pay for a clean.

In June, with the longest days of the year, your panels are doing their most work, which makes it a good time to make sure nothing is holding them back.

Does cleaning solar panels make a difference if it rains?

Rain does help, but it only moves loose dust. The things that really cut output stick fast:

  • Bird droppings. A single dropping shades part of a cell completely, and it bakes on in the sun.
  • Lichen and moss. These creep in from the frame edges, particularly on north-facing roofs or near trees.
  • Traffic and farm dust. Many villages around Cambridge sit next to arable fields, and dust from harvesting and dry soil settles on the glass.
  • Low-pitch panels. On flat roofs, garages and shallow pitches, rainwater pools at the bottom edge and dries into a line of dirt, which can creep further up the panel every year.

How often should solar panels be cleaned?

For most homes, we usually recommend a clean once a year. Panels on a low pitch, under trees, near fields or anywhere popular with pigeons and gulls may need twice a year. Steeply pitched panels in an open spot may go longer.

The best guide is your own generation figures. Signs that output is down because of dirt include:

  • Lower generation than on a similar sunny day at the same time last year, as shown in your inverter or monitoring app.
  • Visible droppings or a grey film when you look up from the garden.
  • A brown or green line along the bottom frame of each panel.

If output has dropped and the panels look clean, the problem may be with the system itself, so it is worth asking your installer to check.

Why use pure water and not detergent?

Detergents leave a thin residue on the glass that attracts dust, so panels get dirty again faster. Some cleaning products can also affect the coating on the glass or the seals around the frame, and panel manufacturers generally advise against harsh chemicals and abrasives. Purified water with the minerals removed dries without spots, so nothing is left behind. Soft brushes are used, never scouring pads, and pressure washers should be kept well away from panels.

Is it safe to clean solar panels yourself?

For ground-mounted panels, a soft brush and a gentle rinse is fine. For anything on a roof, we would not recommend it. Panels should never be walked on or leaned against, ladders on a pitched roof are dangerous, and the system is live whenever light is on it. A professional clean is normally done from the ground or from safe access, without touching the electrics.

Frequently asked questions

How much does solar panel cleaning cost?

We charge from £7 per panel, with a minimum charge of £99.

Doesn’t rain clean solar panels?

Rain rinses off loose dust, especially on steep roofs. It will not shift bird droppings, lichen or the greasy film that builds up over time, and on shallow panels it often leaves a dirt line along the bottom edge.

When is the best time to clean solar panels?

Late spring or early summer, so the panels are clear for the longest, sunniest days. Many cleaners also avoid the hottest part of the day, when cold water on hot glass is best avoided.

How CamClean can help

We offer solar panel cleaning in Cambridge and the surrounding villages, from £7 per panel with a £99 minimum. If your gutters are full of moss and leaves, we can clear those at the same time. Call 01954 783308 or get a quote for your panels.