Solar panels are reliable, but they are not completely hands-off. Like any system exposed to weather and daily use, problems can crop up over time and affect performance. The good news is that most common issues are easy to spot and fix, especially if you know what to look for early on.
1. Too much shade… Not enough sun!
As you might imagine, by far the most common cause of reduced solar output is shading. Although 2025 was officially the sunniest year on record according to the Met Office, the UK still struggles for sun. Just small shadows from trees, TV aerials, chimneys, or nearby buildings can lower generation, and more than you might expect. Leaves or wind-blown debris can have a similar effect.
The fix starts with a visual check at different times of day to see when shading occurs. Trimming back trees, clearing debris, or adjusting panel placement can make a big difference. In some cases, installers may recommend optimisers or microinverters to reduce the impact of partial shading.
2. Dirt, dust, and bird droppings
Over time, solar panels can get dirty. Here in the UK, a bit of rain certainly helps, but it’s like your car — it doesn’t give a proper clean. This layer of dirt blocks sunlight and reduces output.
Fixing this problem is pretty straightforward. Occasional cleaning with water and a soft brush is often enough. For roof-mounted systems, professional cleaning services are safer and more practical. Keeping panels reasonably clean helps maintain consistent performance throughout the year.
3. Inverter faults or failure
The inverter is a key part of any solar system, converting electricity into a form your home can use. It is also one of the most common points of failure. Warning lights, error messages, or a sudden drop to zero generation often point to an inverter issue.
Some problems are temporary and can be resolved by a reset, while others need professional repair or replacement. Regular monitoring makes it easier to spot faults early. Inverters have a shorter lifespan than panels, so replacement after several years is normal!
4. Loose or damaged wiring
Electrical connections can loosen over time due to weather, temperature changes, or poor installation. In some cases, wiring can become damaged by exposure or wear. This can lead to reduced output or intermittent faults. The fix involves a qualified electrician or solar engineer checking and securing connections, and replacing any damaged cables.
This is NOT a DIY job! Hire a pro for any wiring problems. Regular system checks help catch wiring problems before they cause larger issues or safety concerns.
5. Physical damage from weather
Solar panels are built to handle UK weather, but severe conditions can still cause damage. Hail, falling branches, strong winds, or long-term exposure can lead to cracked glass, bent frames, or loose mounts. Physical damage usually shows up as reduced output or visible marks on the panels.
The solution depends on the severity. Minor issues may only need repairs to mounts, while cracked panels often need replacement. After major storms, a quick visual inspection helps spot problems early.
6. Panel degradation and hot spots
All solar panels slowly lose efficiency over time, which is normal. Problems arise when degradation is uneven, often caused by cell defects, shading, or built-up dirt. This can create hot spots, where small areas overheat and affect performance. Hot spots are not always visible but may show up as a steady drop in output.
A professional inspection, sometimes using thermal imaging, can identify the issue. Replacing affected panels or addressing the underlying cause usually restores system performance.
7. Birds and pests under panels
Birds and small animals sometimes nest under solar panels, especially on pitched roofs. While the panels themselves are rarely damaged, nesting materials and chewing can affect wiring. This can lead to faults or reduced output. The fix usually involves safely removing nests and fitting mesh or guards around the panel edges to prevent future access.
Again, this work is best handled by professionals, as it involves roof access and electrical components. Preventative measures can save ongoing repair costs.
