exterior
Solar panel cleaning
Solar panel cleaning costs £5 to £12 a panel with a minimum charge of £60 to £80, so a typical domestic array of twelve panels lands between £70 and £145. The reason to do it is measurable rather than cosmetic: a dirty array on a shallow pitch commonly loses a few per cent of output, and a badly fouled one considerably more.
What this covers
What it costs. Solar panel cleaning costs £5 to £12 a panel, with a minimum charge of £60 to £80 that most domestic jobs land on. Full cost breakdown.
What the job covers
- Panels washed with deionised water from a water-fed pole
- Bird fouling and lichen along the bottom edge of each panel
- Frames and the gap where debris packs behind the array
- Bird proofing mesh fitted around the array
- Ground-mounted and commercial arrays
What is involved
Rain does most of the cleaning on a steep roof and almost none on a shallow one. Below roughly fifteen degrees the water sits instead of running, dust dries where it settled, and the bottom edge of every panel builds a dark band that never washes off. That band is the part that costs output, because a shaded strip across the bottom of a cell string pulls down the whole string rather than its own share.
The water has to be deionised. Tap water dries and leaves the minerals behind, which is a new film on the glass within a day, so the trade uses the same purified water and carbon fibre pole that window cleaners use, and reaches the array from the ground.
Nothing about this involves standing on panels or using detergent. A panel is a sealed unit and manufacturers' cleaning instructions commonly rule both out, and a footprint on the glass can be a microcrack that shows up as lost output years later.
Choosing someone for the job
Ask whether they use deionised water. Tap water and a cloth is worse than leaving it alone.
Ask how they reach the array. From the ground with a pole is the answer; on the roof between the panels is how panels get cracked.
Ask what your inverter reads before and after if you want the number. Anyone who cleans arrays regularly is used to being asked and can usually tell you what to expect for your pitch.
Common questions
How much output does it actually recover?
It depends on the pitch and what is on the glass. A steep clean-looking array gains very little; a shallow one with a dark band along the bottom edge of every panel gains the most, and bird fouling over a cell can cost more than dirt across the whole array.
How often?
Once a year for most domestic arrays, and once every six months where there are trees, a flight path for gulls, or a pitch under fifteen degrees.