Looking after solar panels in Leeds

Does rain do the cleaning?

On a pitched roof, mostly yes. Panels on a slope shed water quickly, and the Met Office stations either side of Leeds record between 116 and 156 rain days a year on their 1991–2020 averages (Church Fenton; Bingley). That is frequent enough to rinse off ordinary dust and pollen before it builds up into anything that matters. What rain does not shift are the stubborn deposits: bird droppings baked on in summer, lichen creeping in from the bottom edge where water lingers, and grime that settles along the lowest row of a shallow array.

Panels on a flat roof or a very low tilt are a different case. Water sits on them and leaves a tidemark of dirt as it dries, so they are worth looking at more often, from a window or the ground where possible. If cleaning is needed, it is a job for someone with proper access equipment and the panel maker's cleaning instructions. Harsh chemicals, abrasive brushes and high-pressure jets can damage the glass coating or the seals around the frame, and a damaged panel is a far bigger problem than a dirty one.

Snow is best left alone. A covering stops output until it slides off or melts, which on a pitched array usually happens once the panels start to warm, and clearing it with a pole from the ground risks scratching the glass, while clearing it from a ladder risks a fall.

Pigeons under the array

The gap between panels and roof tiles is sheltered, warm and hard for predators to reach, which makes it attractive to pigeons in towns and cities, Leeds included. Nesting birds bring droppings, twigs and noise, and the debris can block gutters and hold damp against the roof covering. Bird mesh is the standard fix: a wire or plastic screen fastened round the array's perimeter, sealing the space underneath without any drilling into the panels.

Putting mesh on during the original installation, with the scaffold already up, is much simpler than arranging access again later, so ask whether a quote includes it. If birds have already moved in, the nesting material needs clearing before the mesh goes on, and the contractor should explain how they will deal with any active nests. Signs worth watching for from the ground are birds flying in and out under the panels, twigs poking from the edges, and droppings building up on the lower row.

Moss, leaves and overhanging trees

Where trees stand close to a roof they cause three kinds of trouble. Leaves collect along the bottom edge of the array and in the gutter below, holding damp against the frames. Branches cast shade, and shade on part of an array can drag down the output of other panels wired with it unless the system uses optimisers or microinverters. And moss spreads from shaded, damp tiles onto the edges of the panels.

Cutting back branches that shade the array is often the most useful piece of upkeep a household can arrange, but check before anyone starts. Leeds has 80 conservation areas (Leeds City Council), and trees there, or trees under a preservation order anywhere in the city, need the council's involvement before work; the planning guide covers conservation areas. If a neighbour's tree is the problem, a friendly conversation usually comes before anything else.

Checking output against what Leeds should give

Most systems come with a monitoring app or a display on the inverter, and a glance once a month is the single most useful habit an owner can have. The question is whether the numbers sit in the right range for the month and the roof. PVGIS gives a yardstick: one kW of panels facing south at 35° in the city centre models at 952 kWh a year, an east-facing kW at 753 and a west-facing kW at 740 (PVGIS). Multiply by the size of your system for a yearly expectation. A 4 kW south-facing system in Horsforth would come to about 3,764 kWh, for example, and a 3 kW array facing east in Roundhay to about 2,268 kWh, on our arithmetic. The roof picker gives figures for other slopes.

Monitoring apps usually show two kinds of number. One is power, in kW, at that moment; the other is energy, in kWh, over a day, a month or a year. It is the kWh totals that compare with the table below. A midday power reading will seldom match the system's rated size even on a bright day, because heat and the angle of the sun both trim it, so a 4 kW system showing less than 4 kW at noon is not a sign of a fault. The glossary sets out the difference between kW, kWp and kWh.

Treat the table as a range, not a target. A dull July or a bright March will move a single month well away from the average, so compare a few months together rather than reacting to one. What should prompt a closer look is a drop the weather does not explain: a sunny week with flat output, one string of panels reading far below another, or a month well under half the table's figure. Likely suspects for a sudden stop include the inverter itself, a tripped switch at the consumer unit, or a lost internet connection that leaves the system working but the app blank. The guide to Leeds sunshine explains why winter months look so thin.

How long the parts last

The Energy Saving Trust puts the life of solar panels at 25 years or more and of inverters at around 12 years (Energy Saving Trust). So expect the inverter to be swapped at least once while the panels are still in service. It helps to know the inverter's make, model and warranty end date before anything goes wrong, so a replacement can be arranged quickly. A battery, if you have one, carries its own warranty terms; the battery guide covers those, and the cost of solar in Leeds page shows what systems have cost in the region.

The panels themselves lose output slowly over the years. Their maker's performance warranty states how much output they should still deliver after a set number of years, and a steady year-on-year drift in the monitoring figures is normal. A sudden fall is not.

When an inverter does need replacing, ask whether the new unit has the same rating as the old one. A different size can change the capacity declared to the network, and anything added at the same time, such as a battery, joins the total; the grid connection guide explains how Northern Powergrid counts it. The installer's handover pack should also say what periodic electrical checks the equipment makers advise.

Roof repairs, ladders and paperwork

Never go on the roof yourself, whether to clean panels, clear a nest or look at a fault. A roof with panels is harder to move across than plain tiles, the glass is slippery when wet, and the array produces electricity whenever there is daylight on it. Use someone with proper access equipment, insurance and, for anything electrical, the right competence.

If the roof itself needs work later, such as slipped tiles, a leaking valley or a chimney that wants repointing, the panels over the affected area will have to come off and go back on. That means scaffolding, someone competent to disconnect and reconnect the system, and a check afterwards that everything is producing again. Scaffolding that stands on a Leeds pavement or road needs a licence from the council (Leeds City Council), so ask who is arranging it, and get a price for removing and refitting the panels before agreeing to the roof work.

Keep a folder with the MCS certificate (you can check the installer's certification on the MCS register), the handover pack, the panel, inverter and workmanship warranties, the grid notification and any export tariff paperwork. If the original installer has stopped trading, find out whether it was a member of a consumer code, RECC or HIES for example, and whether its workmanship warranty carried insurance backing. The installer checklist covers what to look for when someone new takes on the system.