Rain, dirt, moss and leaves
Solar panels have no moving parts, and on a pitched roof the rain does most of the cleaning. What it does not shift is anything that sticks: droppings, moss creeping in from the edges, and leaves that settle along the bottom row where the frame meets the roof. Semis and terraces house 45.6% and 26.1% of Wigan's households (Census 2021), and on those roofs an array may share a slope with a chimney stack or sit near a neighbour's tree, so the bottom edge and any shaded corner are the places to look first. Do it from the ground or an upstairs window, with binoculars if that helps.
Never go up on the roof yourself. If dirt, moss or leaves build up enough to matter, use a firm with proper access equipment and ask what it will use on the glass. Check first whether the panel or workmanship warranty sets any conditions about cleaning. A drop in output is the signal that cleaning is worth paying for; a slightly grubby panel after a dry spell is not. Semis and terraces covers how chimneys and hips shape where panels go in the first place.
Pigeons and gulls
The gap between the panels and the roof tiles is sheltered, dry and out of reach, which suits pigeons, and gulls can be a nuisance on roofs too. Nests bring noise, mess on the glass and debris that can block gutters. The usual answer is bird mesh: a wire or plastic mesh fitted round the edge of the array to close the gap, put on by a firm with access equipment.
The easiest moment to fit it is at installation, while the scaffold is up, so ask about it at quote stage. If you add it later, ask whoever fits it how the mesh is held on, because the panels and their frames are covered by warranties, and tell the original installer. Timing matters as well: GOV.UK lists it as an offence to intentionally take, damage or destroy a wild bird's nest while it is being used or built (GOV.UK), so get advice before anything is cleared from under the panels in the nesting season.
Checking the output against Wigan's figures
If the system has a display or an app, read it once a month and keep a note; the monthly pattern tells you far more than any single day. PVGIS puts a south-facing panel at its best angle in central Wigan at 113 kWh per kW in June and 28 kWh in December, so a 4 kW system there would make roughly 452 kWh in June and 112 kWh in December in an average year (PVGIS 5.3, our arithmetic).
Where in the borough you live hardly moves those numbers. For a south roof at 35°, the 12 places modelled run from 911 kWh per kW a year in Atherton and Tyldesley to 936 kWh in Orrell, a spread of 2.7% (PVGIS 5.3, our arithmetic). Direction moves them far more: an east-facing roof in central Wigan makes about 20% less than a south-facing one. Find your place and direction on output across the borough, multiply by the system's size in kW, and compare with the installer's written estimate, remembering that any single year can run above or below an average taken over 2005-2023.
Two patterns are worth acting on. A sharp drop on bright days, compared with the same month last year, points to a fault, perhaps in the inverter or a connection. A slow slide over several months may be dirt, a tree growing into the light or a failing panel. Either way, note the readings and the dates before you contact anyone, because they are the evidence the installer will ask for. The yardstick that counts in any complaint is the installer's own written estimate: RECC says its members follow strict rules for calculating performance estimates and tells buyers to get one in writing (RECC), so keep it with the readings.
| What | How | If something is wrong |
|---|---|---|
| Output | Note the monthly reading; compare with the same month last year and the PVGIS figure | The installer, with the readings |
| Inverter display | Glance at it when you take the reading and note any fault code | The installer, then the inverter's warranty |
| Panels and edges | Look from the ground for droppings, moss, leaves and nests | A firm with access equipment; never the roof yourself |
| Bird mesh | Check it is still in place after high winds | Whoever fitted it |
| Roof work | Before any repair under or near the array | The roofer and a solar firm, together |
| Paperwork | Keep certificate, handover pack, network notice and export contract together | The installer, then MCS, for a missing certificate |
The inverter, the warranties and who to contact
The panels and the inverter age differently. The Energy Saving Trust puts the life of the panels at 25 years or more and of the inverter at around 12 years (Energy Saving Trust), so expect the inverter to need replacing at least once over the life of the panels. A replacement is not always like for like: Electricity North West takes a system's rating from its inverter (Electricity North West), so a bigger replacement, or one that also runs a battery, can change the network paperwork. If its display shows a fault or goes blank, look up the code in the manual first, then contact the installer with the code and the readings.
Who to contact depends on what failed and when. Within the workmanship warranty, the installer comes first: a RECC member must give a workmanship warranty of at least two years covering problems caused by incorrect installation, backed by financial protection if it fails to put things right or stops trading (RECC). The panels and the inverter carry their own manufacturers' warranties, which should be in the handover pack along with how to claim on them. If the installer will not help, when an installation goes wrong sets out what to do next, in order.
Roof repairs mean lifting the panels
Anything that needs doing to the roof under the array, from a slipped tile to a full re-roof, means taking the panels off first and putting them back afterwards. That usually means scaffolding again, and a solar firm to disconnect and reconnect the system safely. Before agreeing a roof job, ask the roofer and a solar firm to price their parts together, and ask how removal and refitting affects the panel, inverter and workmanship warranties. If a leak appears within the workmanship warranty period and could be linked to the fixings, tell the installer in writing before anyone else touches the roof, so that the warranty claim is not lost.
This is one reason the roof's condition belongs in the conversation before solar goes up at all. A quote should say whether the installer has checked the roof covering and how long it is likely to last under panels expected to work for 25 years or more; what a quote should include covers the survey, and the costs page explains why access and scaffolding are a real part of the price.
Keep the paperwork together
Keep four things in one folder, paper or digital: the MCS certificate, the handover pack with the warranties and manuals, the notice the installer sent to Electricity North West, and the export tariff contract. MCS says the installer must issue the certificate within 14 days of commissioning, or 30 days if it is certified under MCS's redeveloped scheme, and that for a copy or a correction you go to the installer first (MCS). Corrections are possible, for example after a meter change or a mistake when the certificate was made; MCS handles copies and amendments itself only where the installer is no longer certified or no longer trading. The folder is the first thing to hand to anyone who works on the system, and to a buyer if you sell. Electricity North West and your panels explains the network notice, and export payments the tariff.
MCS has added one more reason to keep it handy. It says that from May 2026 its Customer Insights team is contacting a selection of customers with an MCS certified installation, to verify their MCS certificate and make sure the installation was delivered to their satisfaction (MCS). If someone gets in touch about your system and you are unsure who they are, end the conversation and contact MCS through its own website, not through details the caller gives you. Checking a solar installer lists the registers worth bookmarking.