How to choose a solar panel cleaner: questions to ask and red flags

Updated 6 November 2026 · By the Solar Panel Cleaners team

Short answer: Choose a solar panel cleaner who uses purified water and soft brushes on water-fed poles, works from the ground wherever possible, uses no detergents, scrapers or pressure washers, and gives a fixed price for the whole array. Ask how they will reach your panels, whether they will walk on the roof, and what happens if panels are damaged. Be wary of very cheap door-to-door offers and anyone who suggests pressure washing.

Why the choice matters

Solar panel cleaning looks simple, but the wrong method can do lasting harm. The front glass of most modern panels has an anti-reflective coating that helps more light reach the cells. Abrasive pads, blades and high-pressure water can scratch or wear that coating, and scratches cannot be polished out. Walking on panels can crack cells inside the glass, sometimes without visible damage, and walking on tiled roofs breaks tiles and creates leaks. A good cleaner protects the panels, the roof and the people doing the work.

Because cleaning is not a regulated trade, anyone can offer it. That is why asking a few direct questions before you book is worth doing.

Questions to ask before booking

Question	What a good answer sounds like
What water do you use?	Purified water from reverse osmosis and deionisation, with no detergent
What touches the glass?	Soft-bristle brushes designed for glass or panels
How will you reach the panels?	From the ground with water-fed poles, or a planned safe access method
Will anyone stand on the roof or panels?	No, unless there is a planned and safe reason such as proofing
Is the price for the whole array?	Yes, one fixed price covering every panel and frame
What happens if you find damage?	It is not cleaned over, it is photographed and reported to you
Do you check your water purity?	Yes, with a TDS meter, ideally reading zero or close to it

Red flags to watch for

Offers to pressure wash the panels or roof at the same time
Use of washing-up liquid, bleach or unnamed chemicals on the glass
Scrapers, blades or scouring pads for lichen or droppings
Plans to walk on the panels or tiles to reach the top row
Door-to-door cold calls with a price that changes once they are on site
Claims that cleaning will boost output by a fixed large percentage regardless of soiling
Pressure to sign up to a long contract before the first clean
No clear answer about how they will deal with damaged panels

A cleaner who promises a set percentage gain is guessing. The improvement depends entirely on how dirty the panels were, and lightly soiled panels may gain very little.

Comparing quotes fairly

Prices for a typical house usually fall between £80 and £180, often based on roughly £4 to £15 per panel with a minimum charge. When comparing quotes, make sure each one covers the same thing. Some include every panel on every roof face, while others quote only the main array. Some include lichen removal, while others add it on the day. Some include the visual check and a short report, while others say nothing.

Confirm the panel count each cleaner has priced for
Ask whether heavy fouling or lichen is included or extra
Check whether panels on garages, extensions or outbuildings are included
Ask whether bird proofing would be quoted separately
Confirm whether the price changes for three-storey or awkward access

Safety and access

Under the Work at Height Regulations 2005, anyone carrying out work at height for a business must plan it properly and avoid working at height where it is reasonably practicable to do the job another way. For panel cleaning, that usually means water-fed poles from the ground. When roof access is genuinely needed, for example for bird proofing or a flat roof, ask what equipment will be used, such as a scaffold tower, roof ladder, mobile platform or edge protection.

If your array is on a commercial or agricultural building, ask about fragile roof lights and fibre cement sheets. These can give way under a person's weight, and a competent cleaner will plan around them rather than walking across them.

What a good job looks like afterwards

Once the panels have dried, they should look evenly clear from the ground, with no streaks of dirty water along the bottom frames and no patches missed at the top or the far corners of the array. Small faint marks where heavy lichen once sat can remain, as lichen can lightly etch the surface over years, but loose dirt, droppings and green growth should be gone. The gutters below may collect some rinse water and loosened debris, which is normal.

Panels evenly clear across every row, including the top row and corners
No white mineral spots, which suggest the water was not fully purified
No scratches, swirl marks or chips that were not there before
Frames and the gap along the bottom edge cleared of moss and grit
A short message or note confirming the job and anything found
Generation over the following clear days in line with or better than before

If something looks wrong, such as streaking or missed panels, raise it straight away with a photo. A careful cleaner will usually come back and put it right, and it is much easier to judge while the clean is recent.

Before the day

Send a clear photo of every roof face with panels
Tell the cleaner about pigeons, nests or damaged panels you already know about
Make sure side gates can be opened and parking is available nearby
Move cars away from directly below the array if possible
Check your panel warranty for any cleaning guidance from the manufacturer

A good cleaner will be happy to answer these questions before you book. Clear answers about method, access and price are the best sign you will get a careful job.