The case for professional cleaning
Professional solar panel cleaners use a pure water fed pole system — deionised water delivered through a brush on an extendable pole from ground level. Because the water is deionised (mineral content near zero), it leaves no limescale residue when it dries, which is the main cause of streaking and filming when tap water is used.
Working from ground level eliminates the roof-access risks entirely. A professional cleaner for a standard two-storey house will typically complete the job in 30–60 minutes. For a 4kW system on a pitched roof, professional cleaning typically costs £50–£120 depending on access, location, and system size.
Professional cleaning also typically includes a visual inspection of the panels for obvious damage, loose frames, or mounting issues — a useful secondary benefit.
The case for DIY
If your panels are on a single-storey roof, a conservatory, or a ground-mounted frame, DIY cleaning becomes genuinely accessible. The main requirement is the right water — tap water is too mineral-rich in most UK areas and will leave residue that can itself block light transmission over time.
A domestic deionised water system or a TDS (total dissolved solids) meter to verify your water source produces water below around 30ppm is the minimum for DIY work without a professional grade pure water system. Combined with a soft wash brush and a long handle, this is achievable for around £50–£100 in equipment.
For ground-mounted or single-storey panels only: a garden hose with a gentle spray attachment is sometimes used for light dust removal, but is not a substitute for a proper pure water system for anything more than surface dust.
What to avoid
Pressure washers are the most common DIY mistake. High-pressure water can force water past panel frame seals, cause micro-cracking in the glass, and strip anti-reflective coatings. Most panel warranties explicitly exclude damage caused by pressure washing. Do not use a pressure washer on solar panels.
Abrasive materials — sponges with a scouring side, wire wool, rough cloths — scratch the glass surface. Even fine scratches accumulate light scatter over time and reduce transmission. Use only a soft-bristle brush or a lint-free microfibre cloth.
Cleaning agents other than plain water or a mild, residue-free solar panel cleaning solution should be avoided. Household detergents, window cleaners, and especially anything containing bleach or ammonia can strip coatings or react with panel materials.
Working on a pitched roof without appropriate fall arrest equipment is a significant safety risk. Falls from roofs are a leading cause of serious injury and death among tradespeople and householders in the UK. If your panels require roof access, use a professional.
Warranty considerations
Check your panel manufacturer's warranty documentation before attempting DIY cleaning. Many major manufacturers (LG, SunPower, Panasonic and others) specify that cleaning must be carried out using approved methods and in some cases by qualified personnel. Damage caused by non-compliant cleaning methods is typically excluded from warranty coverage.
An MCS-certified cleaning company will operate in compliance with manufacturer guidelines. Using a professional is the safest position if warranty preservation is a priority.