The most common solar panel problems in the UK are shading and dirt build-up (both cut output without anything being “broken”), followed by inverter faults, loose or corroded connectors, and microcracks from hail or thermal stress. Most show up as a gradual drop in generation rather than a sudden failure, which is exactly why checking your monitoring app every so often matters more than waiting for something to look obviously wrong.
The Most Common Solar Panel Problems, Ranked by Frequency
| Problem | How it shows up | Typical fix |
|---|---|---|
| Shading (trees, chimneys, aerials) | Output dips at predictable times of day | Trim vegetation, reposition affected panels, or add optimisers |
| Dirt, pollen, bird droppings | Gradual output decline across the whole array | Clean panels 1–2 times a year |
| Inverter faults | Sudden drop to zero generation, error code on display/app | Restart per manufacturer guidance; call installer if it recurs |
| Loose or corroded connectors (MC4) | One string underperforming, intermittent output | Professional inspection and reseating/replacement |
| Microcracks (hail, thermal stress, poor handling) | Slow decline in one panel’s output, sometimes invisible to the eye | Thermal imaging survey; panel replacement if under warranty |
| Bird nesting under panels | Debris, noise, occasional wiring damage | Bird proofing mesh fitted around panel edges |
| Snow or ice cover | Zero output for hours or days in winter | Usually resolves itself; avoid manually clearing panels |
| Potential-induced degradation (PID) | Whole-string efficiency loss over months/years | PID-resistant inverter settings or panel replacement |
Shading and Dirt: the Two “Problems” That Aren’t Really Faults
Together, these probably account for more lost generation across UK homes than every mechanical fault combined, and neither means anything is actually broken. A chimney, satellite dish or nearby tree can shade part of an array at predictable times of day, dragging down a whole string rather than just the shaded cells. Pollen, dust, bird droppings and general grime build up gradually enough that most homeowners don’t notice the decline until they compare this year’s generation to last year’s. Our guides to solar panel shading and cleaning solar panels safely go into both in more depth.
Inverter Faults: the Most Common Hardware Problem
Inverters do more work and contain more electronics than the panels themselves, which is why they fail more often. A sudden drop to zero generation, an error code on the display or app, or a status light that’s changed colour usually points here first. Most inverters have a shorter warranty than the panels (commonly 5–12 years against 20–25 for panels), so it’s worth knowing your inverter’s specific warranty terms rather than assuming the whole system is covered for the same length of time.
Wiring and Connector Faults
MC4 connectors join panels together in a string, and like any outdoor electrical connection, they can loosen or corrode over years of temperature swings and weather. This tends to show up as one specific string underperforming, or output that fluctuates in ways that don’t match the weather. It’s not something to investigate yourself given the voltages involved – this is a job for your installer or another MCS-certified professional with the right isolation and testing equipment.
Microcracks and Hotspots
Microcracks can form from hail impact, extreme thermal cycling, or rough handling during installation, and they’re often invisible without a thermal imaging camera. Left unaddressed, a cracked cell can develop a “hotspot” – a localised area that heats up more than the rest of the panel, accelerating further damage and, in rare cases, posing a fire risk. If your monitoring shows one panel consistently underperforming its neighbours with no obvious shading cause, this is worth flagging to your installer for a proper inspection rather than assuming it’ll sort itself out.
Bird Nesting and Pigeon Damage
Pigeons in particular like the sheltered, warm gap between panels and the roof, and once a pair nests there, droppings and debris can build up quickly, occasionally damaging cabling. Bird-proofing mesh fitted around the edges of the array during or shortly after installation is a one-off cost that avoids what can otherwise become a recurring problem. If you’re already seeing birds around your panels, our guide to protecting your solar panels covers proofing options in more detail.
When to Call a Professional vs When to Wait It Out
Snow, ice and heavy overcast weather cause genuine but temporary output drops that resolve on their own – there’s no need to call anyone out for these, and manually clearing snow from panels can do more harm than good. What’s worth flagging to a professional: a sudden drop to zero generation that persists after a routine inverter restart, one panel or string consistently underperforming with no shading explanation, visible physical damage, or any burning smell or unusual noise from the inverter. Our guide to fixing underperforming solar panels walks through the troubleshooting steps in more detail.
Frequently Asked Questions About Common Solar Panel Problems
Why has my solar panel output suddenly dropped?
The most likely causes are a temporary weather event, new shading (a tree that’s grown, scaffolding next door), an inverter fault showing an error code, or dirt build-up if it’s been a while since cleaning. Check your monitoring app for error codes first, then rule out shading and dirt before assuming there’s a hardware fault.
Are microcracks in solar panels covered by warranty?
Usually yes, if they’re caused by a manufacturing defect or occurred within the warranty period without obvious external damage like a falling branch. Most panel manufacturers offer 20–25 year performance warranties, but you’ll typically need documented evidence (often a thermal imaging report) to make a claim.
Can pigeons really damage solar panels?
Indirectly, yes. Pigeons themselves rarely damage the panels, but nesting debris and droppings can clog drainage, corrode fixings over time, and occasionally damage cabling underneath the array. Bird-proofing mesh is a cheap way to prevent this becoming an ongoing issue.
How do I know if a problem is serious enough to call my installer?
Treat a persistent zero-output reading, one panel or string clearly underperforming its neighbours, visible physical damage, or any burning smell as reasons to call straight away. A temporary dip on a cloudy or snowy day generally isn’t cause for concern and should recover on its own.
Do solar panels need regular professional servicing?
Not usually on a fixed schedule, but a periodic check – roughly every few years, or sooner if your monitoring shows a decline you can’t explain – can catch microcracks, connector wear or inverter issues before they get worse. Our solar panel maintenance checklist covers what to look at yourself between professional checks.
