Solar panel servicing, fault finding and repair

The clearest sign is a comparison: this month's generation against the same month in earlier years, taken from the generation meter or the monitoring history. A sudden drop to zero usually means the inverter has shut down or tripped. A gradual fall of a noticeable amount can point to one string not working, shading from a growing tree, or a failing panel or connector.

Other signs include error codes or warning lights on the inverter, a monitoring app that has stopped reporting, a burning smell or scorch marks near the inverter or isolators, water staining in the loft below the array, and birds nesting under the panels. Anything that looks like heat damage is a reason to call an installer promptly, not to investigate yourself: the panels keep producing voltage whenever there is daylight, even when the inverter is off.

The inverter is the part most likely to fail during the life of a system, and many older inverters are no longer supported by their makers. A repair visit should start by reading the fault log and testing the strings, so you do not replace an inverter when the real fault is a failed isolator or a damaged cable.

If replacement is needed, it is the moment to decide whether you want a battery in the future. A hybrid inverter can make that later step simpler. The replacement should match the array's voltage and current, and your network operator may need to be told if the inverter's rating changes. If the system earns Feed-in Tariff payments, Ofgem expects you to notify your FIT licensee about modifications to the accredited installation, and the generation meter must keep recording correctly.

Pigeons like the sheltered gap under panels. Their nests and droppings can damage cables, block drainage and make a mess of guttering. Mesh fitted around the edge of the array keeps them out; it has to be clipped to the panel frames rather than drilled into them, and any existing nests have to be dealt with in a way that respects wildlife law during the nesting season.

Leaks around roof fixings are less common but serious, because water can run along rafters for some distance before it appears. The repair usually involves lifting panels, so scaffolding or another safe access method is needed.

In most of the UK, rain keeps panels clean enough. Cleaning is worth it mainly on low-pitch roofs, near farms or busy roads, or under trees. It is work at height on a fragile surface, so it belongs with a firm that has the equipment and insurance for it.

Many systems were fitted by firms that no longer trade. That does not stop another installer from servicing or repairing the system, but it helps to have the paperwork: the MCS certificate, the electrical installation certificate, the inverter and panel data sheets and any warranty documents. If you have lost the MCS certificate, MCS can provide a copy on request. Manufacturer warranties on panels and inverters may still be valid even when the installer's workmanship warranty is not.

• what will be tested: string voltages and currents, insulation resistance, isolators, earthing, inverter log
• access method and whether scaffolding is included
• the likely cause of the fault and how it was diagnosed
• replacement parts with models, and whether they are compatible with the existing array
• any notifications to the network operator or your FIT licensee
• a test certificate for the electrical work after the repair

Describe the symptoms, the age of the system and the inverter model, and verify your phone and email. Solar firms in your area see the request without your personal details, and one business can buy it. That business pays Offrano; you pay nothing, and the request then leaves the shop.

We email you the firm's name, address and phone number before it sees your details, and you can withdraw consent at any time. If nobody buys the request within 21 days, it is withdrawn. Offrano checks only that buyers are registered businesses, so ask about experience with your inverter brand and check certification yourself.