Why clean?
You paid for an array that turns daylight into money. Everything that lands on the glass between now and the day it's cleaned is taking a cut.
The cost of doing nothing
How much you lose depends almost entirely on where the array sits and what's around it. A clean array on a steep roof in open country loses very little. A shallow-pitched array near trees, farmland or a main road loses a great deal more.
Airborne dust and road grit. Tree pollen in spring. Bird droppings are the worst offender, because they're opaque and they bond hard. Moss and lichen creeping in from the frame edges. On farms, a fine layer of everything the fields throw up.
Panels are wired in series. Heavy shading on one cell can drag down the string it sits in, so a single well-placed splat of bird mess costs you more than a thin film across the whole array. It's not proportional, and that surprises people.
Grime holds heat and moisture against the glass and the frame seals. Lichen roots into edge sealant. Left long enough, a cleaning job quietly turns into a repair job, and we don't do repairs, so there's nothing in it for us to say that.
The biggest myth
If rain cleaned solar panels, nobody would ever wash a car.
Rain doesn't arrive clean. It picks up dust and pollen on the way down, spreads it across your glass, and then evaporates, leaving every solid it was carrying behind as a film. That's why a car left out in a downpour comes out spotted, not sparkling.
And rain has no answer at all to the things that cost you the most output: bird droppings that have baked on, lichen anchored into the frame edge, moss growing up from the bottom rail. Those need contact and the right products. Weather won't do it.
Our method
We clean with fully certified, environmentally friendly cleaning products, applied through a soft brush on a telescopic pole. Effective on the grime, gentle on the glass, and safe for whatever the water runs off onto.
Solar glass isn't ordinary glass. It carries an anti-reflective coating whose entire job is to let more light through, and that coating is what harsh cleaners and abrasives destroy. Once it's gone, it doesn't come back, and you've permanently lost a slice of the output you were trying to protect.
So the products we use are chosen to do two things at once: lift dust, pollen, bird mess and lichen off the surface properly, and leave the coating, the seals and the frame exactly as they were. They're certified for the job and they're kind to the ground, the plants and the drains the run-off ends up in, which matters when you're rinsing a roof above someone's garden.
We don't jet wash. High-pressure water drives past the seals and can crack cells outright. Abrasive pads and scouring are out for the same reason, and so are harsh household chemicals, which leave a film that attracts dirt faster than bare glass did. Nobody stands on your panels either: foot pressure causes microcracks you'll never see and can never undo.
Doing it yourself with a hose and a broom is where most panel damage comes from, and that's before we get to the ladder. Here's why we say leave it to someone trained.
When to do it
Once a year covers most domestic roofs. These are the things that push it to twice.
Sap, leaf debris and a lot more bird traffic overhead. The single biggest accelerator we see.
Airborne dust, muck and exhaust film build a greasy layer that rain genuinely cannot lift.
Under about 15 degrees, water sits rather than runs. Flat-ish arrays soil faster and hold it longer.
Hilltop and coastal positions catch wind-carried grit and salt, and grow lichen faster than sheltered ones.
Not sure which bracket you're in? Tell us your postcode and what's around you, and that's usually enough for us to say honestly whether you need us once a year, twice, or not yet.
Straight answers
For most UK roofs, yes. Soiling typically costs an array somewhere between 5% and 25% of its output, depending on how dirty it's got, where it is and how steeply it's pitched. Panels near trees, farms, busy roads or in exposed hilltop positions sit at the worse end of that range. A clean doesn't make panels better than new. It stops you giving away output you've already paid for.
No. If rain cleaned solar panels, nobody would ever wash a car. Rain carries dust and pollen down onto the glass and then evaporates, leaving the solids behind as a film. It also can't shift bird mess, lichen or moss, which bond to the glass and the frame edges. Rain moves grime around a panel. It doesn't remove it.
Once a year suits most domestic roofs. Twice a year is worth it if you're near trees, farmland, a main road or a building site, or if you get heavy bird traffic. Commercial and agricultural arrays are usually on a six-monthly cycle, because the soiling is faster and the lost output is worth more.
Fully certified, environmentally friendly cleaning products, applied through a soft brush on a telescopic pole. They're chosen to lift grime without attacking the glass or its anti-reflective coating, and to be safe for the ground, plants and drains the water runs off into. We never jet wash or use abrasive pads, and nobody stands on the panels. More on how we clean.
Not when it's done properly. Panel manufacturers specify gentle cleaning with a soft brush and nothing abrasive, which is exactly how we work. What does put a warranty at risk is jet washing, abrasive pads, harsh household chemicals, or walking on the panels, all of which can crack cells or damage seals.
Spring is ideal. Once tree pollen has settled and before the strongest sun of the year, you get the benefit through the highest-output months. Autumn is the next best, clearing leaf debris and moss before winter. We work year-round, but we won't put anyone on a roof in high winds, ice or heavy rain.
You can. We'd rather you didn't, and not because we want the work. It's two separate dangers stacked on top of each other: a ladder against a gutter with wet glass above it, and an array generating live DC electricity that has no off switch. Falls from height are one of the biggest causes of death and serious injury at work in the UK, and a domestic roof doesn't become safer because it's yours. Here's what we're trained and insured to do about both.
No. It's one of the fastest ways to ruin an array. High-pressure water drives past the panel seals, can crack cells outright, and damages the anti-reflective coating on the glass. Manufacturers specify gentle cleaning with a soft brush. Pressure washer damage is also precisely the sort of thing a warranty claim gets refused for.
It depends on how many panels you've got, the pitch of the roof, and how we can safely reach it: a straightforward bungalow and a steep three-storey terrace are very different jobs. We give free, no-obligation quotes based on your actual roof rather than a number pulled out of the air. Send us your details and you'll get a real figure back.
Free, no-obligation quote. Tell us roughly where you are and how many panels you've got, and we’ll come back to you, usually the same day.