Solar panel maintenance in the UK: what needs doing

Solar panel maintenance in the UK is mostly a job for your eyes and your phone, not a ladder. There are no moving parts on the roof, the rain does the washing, and the thing most likely to need attention is sitting in your loft or garage rather than up on the tiles.

What follows is what I would do at my own house, in the order I would do it, after fifteen years of going back to arrays that were fitted long before that. The kit itself is on the solar panels page.

What does solar panel maintenance in the UK actually involve?

Three things, and only one of them is regular.

Monthly, from the sofa. Open the monitoring app. Look at this month against the same month last year. Weather moves the numbers around, so year on year is the comparison that means something, not week on week.

Yearly, from the garden. Stand back and look at the array. You are checking for anything that has appeared: a bird's nest under the panels, moss creeping up the lower row, a branch that has grown into the sun path, a panel that looks dirtier than its neighbours.

Every three to five years, by somebody with the right kit. A proper check of the fixings, the DC connectors, the isolators, the inverter and the earthing, plus a look at the tiles around the hooks. That is the visit that finds problems before they are expensive.

Do solar panels need cleaning?

Usually less than the people selling cleaning would like.

Glass on a pitched roof sheds most dirt when it rains. The exceptions are real, though, and I see all of them around here.

Shallow pitches, where water sits instead of running, build up a tidemark along the bottom edge of the glass. Arrays under trees collect leaf debris and sap. Roofs near landfill, a river or the flight lines the gulls use in Rotherham get a lot more mess than a roof three streets away. Farm buildings collect dust in summer.

If you do need a clean, it wants deionised water and a soft brush on a pole, from the ground where possible. No detergent, no pressure washer, and never cold water onto hot glass, because thermal shock cracks panels. If somebody is proposing to walk on your array to clean it, that is the end of the conversation.

A pigeon mesh around the edge of the array is worth more than any number of cleans. Nesting under panels is the single most common mess I get called to.

How do I check my solar panels are working?

Start with the app, because it will tell you more than a look at the roof will.

Compare this month with the same month last year. A drop of a few percent is weather. A drop of a third is a fault. If your system reports per-string or per-panel, look for one string that has fallen behind the other: that is usually a DC connector or a single shaded panel rather than a dead array.

Then check the obvious physical things. The inverter should have a steady light and no error code on its display. The generation meter, if you have one, should be counting up on a bright day. Your import and export figures on the smart meter should show export on a sunny afternoon when the house is empty.

If the inverter is showing a fault code, write it down before you reset anything. That code is what tells an engineer whether it is a grid fault, an insulation fault or the unit itself.

What actually goes wrong?

The inverter. This is the one. It is the part with electronics working hard every day, and it is the part most likely to be replaced during the life of the system. Budget for it rather than being surprised by it.

DC connectors. Cheap or badly crimped connectors are the cause of most mysterious output drops, and occasionally worse. Good ones matched to the same manufacturer last.

Birds. Nesting under the array, which blocks airflow, drops debris on the tiles and makes a noise you will not enjoy.

Isolators. The outdoor rotary type suffers in the weather. A seized or water-ingressed isolator is a common find on older systems.

Panels themselves. Rarely. Micro-cracks from someone standing on them during roof work, or hot spots from long-term shading. The glass itself is tough.

I have taken the covers off ten-year-old arrays where every panel was still performing and the only thing that had failed was the inverter and a pair of connectors.

What does solar panel servicing cost in the UK?

It depends almost entirely on access, which is not a dodge: it is the actual answer.

A ground-level check of the inverter, isolators and paperwork is a short visit. The same check with the roof included may need a tower or scaffold, and scaffold is the biggest single line on any roof job. A repair to a DC connector at the top of an array on a three-storey terrace costs several times what the same repair costs on a bungalow.

So get it priced as a job, in writing, before anyone attends. Ask what the visit includes, whether roof access is in the price, and what happens if they find something. Anyone quoting a flat annual figure without knowing your roof is quoting a subscription, not a service.

A worked example: a 4.8 kWp array after five years

Take the system we fit most: ten LONGi Hi-MO X10 panels and a Hanchu 5 kW hybrid inverter on a Rotherham semi, making between 4,500 and 4,800 kWh a year.

Five years in, the owner notices July has come in noticeably below the last two Julys. The app shows one string behind the other. On site it turns out to be a pigeon nest under the bottom row of the west side, with droppings across the lower edge of three panels and a partly shaded cell.

Clean, mesh fitted round the array, connectors checked while the tower is up. Output back to where it was. Nothing was broken, and nothing needed replacing. That is what most maintenance looks like.

What I would not pay for

An annual clean on a steep, clear, unshaded roof. A monitoring subscription for data your inverter already gives you for nothing. An extended warranty sold at the door years after the install by a company that did not fit it.

If a caller tells you your system has been flagged as underperforming and they have never seen it, hang up. Nobody can see your generation figures without your account.

How solar panels work explains what each part is doing, and are solar panels worth it deals with the maintenance myths people arrive with.

If your output has dropped and you want somebody to look properly, Get a quote with your postcode and what your app is showing. We service systems we did not fit. Or ring 01709 278248.