Solar panel cleaning in Shrewsbury, from £6 a panel

What a panel clean costs, and what moves it

£6 a panel. That is what I work from for a standard domestic array in and around Shrewsbury, and it is a figure I confirm with you before I start rather than one that quietly grows once I am on the drive.

Because it is priced per panel, the count does most of the work. What moves it beyond that:

• Height and standing room. A bungalow roof in Bayston Hill and a tall town house near Town Walls are not the same job to reach from the ground.
• Roof or frame. A ground-mounted array sat on a frame in a garden or along a field edge is the simplest of the lot to get to.
• How bad it has got. A first clean after several years, with moss banked along the bottom edge of every panel, is heavier going than an annual tidy up.
• How many elevations. Plenty of roofs carry a run on the back and a second run on a side, and each one has to be set up for separately.

For a large agricultural or commercial array, send me a panel count and a photo that shows the access, and I will come back with a figure for the job before anything is booked. If you only have a handful of panels, it is worth putting them on the same visit as a window clean or a gutter clear so I am not making a trip out for those on their own.

What the dirt is actually costing you

A dirty panel makes less electricity than a clean one. How much less depends completely on what is sitting on it, which is why I will not quote you a percentage and would be wary of anyone who does.

The part most people get wrong is assuming an even layer of dust is the problem. It is not, particularly. A thin film across the whole array shaves a little off the top and no more. The expensive dirt is small, dark and stubborn: a band of moss along the bottom edge of a panel, a lichen patch, a good splat of bird mess. The cells inside a panel are wired in groups, so shading one cell drags on every cell in its group rather than just its own patch of glass. A hand-sized mark in the wrong place costs you more than a whole roof of light dust.

The other thing working against you is that none of it announces itself. Output falls away gradually over years, the weather changes month to month, and nobody notices a slow decline. If you want to see it, compare the same month against the same month a year or two back on your generation meter or in your inverter app, rather than comparing June with October and drawing conclusions.

What a clean is worth to you then depends on the size of the array, what it is exporting or offsetting, and how far it had been left. That is your sum to do rather than mine, and I would rather you did it properly than took a salesman's figure on trust.

How often panels genuinely need doing around Shrewsbury

For most Shrewsbury houses, once a year covers it. Two things push it to twice: what lands on the glass, and the angle it lands at.

Out on the farmland edge, towards Bicton and Shelton or beyond Bayston Hill, harvest is the event that decides it. Combining and baling put a fine dust over everything for weeks, muck spreading follows on behind, and it does not blow off a panel the way it blows off a wall. If your array looks out over that ground, a clean booked after harvest is worth more than the same clean booked at any other point in the year.

Pitch matters just as much. A steep roof sheds water in sheets and stays reasonably honest between cleans. The shallow pitches you get on a lot of the newer estate builds, and any array sat nearly flat on a frame or a garage roof, hold water where it lands, and water that sits leaves behind everything it was carrying as it dries. Same story on any panel with trees over it, which is common on the older streets around Belle Vue, Monkmoor and Copthorne, where sap and honeydew are sticky enough to hold dust in place until something takes them off.

Do not count on rain. It moves the loose material down the glass and leaves the fine stuff banked in a dark tide line along the bottom edge, which is exactly where moss and lichen get their start. Spring is the sensible booking: after winter has finished dirtying them, and before the long days that actually pay.

Why nobody should be walking on your array

Panels get cleaned the same way I clean windows, with de-ionised water fed up a pole to a soft brush head and worked over the glass from ground level. The minerals are stripped out of the water, so it lifts the dirt and then dries without the spotting or chalky film tap water leaves behind. No detergent goes near it, because anything that foams leaves a residue, and a residue is simply something for the next fortnight of dust to stick to.

Both feet stay on the ground, and that is not a slogan. A panel is glass laminated over cells on a light frame. Body weight on it can crack cells inside that laminate, and cracked cells are invisible from the garden, so the first you hear of it is a generation figure that never comes back. The same goes for leaning a ladder on the panel frame or on the plastic gutter underneath it.

There are three other ways an array gets ruined by a clean, all of them avoidable. Abrasives: panel glass carries an anti-reflective coating, and a scouring pad, a blade or a stiff bristle brush will mark it permanently. Tap water: it dries with its minerals still in it and leaves a film that passes less light than the dirt you started with. And pressure, which can force water past the seal at the panel edge, and on some panels that is enough to affect the warranty.

Getting to the glass on a Shrewsbury roof

The middle of town is timber framing, Georgian frontages and conservation streets like Town Walls, so you rarely see a panel on a front elevation there. Nearly all the solar work I do is on the ring of estates: Radbrook, Sutton Farm, Meole Brace, Bayston Hill, Copthorne and Monkmoor, plus the newer developments where the array arrived fitted with the house. Those are mostly standard tiled roofs that I can get to from a drive or a lawn.

Out towards Bicton and Shelton it changes character again: barn roofs, workshop roofs, and frames sat in a paddock or along a field edge. Ground-mounted arrays are the easiest of all to clean and often the dirtiest going, because they catch everything thrown up off the ground beneath them.

Access gets checked before I give you a price, not after. If a pole cannot get to an array safely, because of the standing ground, a steep bank, or the only approach being through next door's garden, I will tell you that plainly instead of improvising on a ladder. No panel clean is worth the risk of taking, or the damage a rushed one leaves behind.

Who you are calling

TD Exterior Cleaning is Jack, working on his own across Shropshire since 2011, based in Shrewsbury at SY3 6AP and fully insured for domestic and commercial work. 46 five-star Google reviews, a 5.0 rating, and 169 recommendations on Facebook.

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