Common Solar Panel Faults & How to Spot Them (UK 2026)

Updated: June 2026 • Energy Solutions NW This guide covers the most common solar panel faults, the warning signs to watch for, and what to do — for homeowners in the North West.

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The Warning Signs to Watch For

Most faults reveal themselves in one of a few ways.

• • A drop in output: the clearest early signal — your monitoring app or meter shows less than expected.
  • Inverter error codes: warning lights or messages on the inverter display.
  • Visible marks: cracks, discolouration, burn marks or bubbling on a panel.
  • Higher bills: often the first thing homeowners notice, before checking anything else.

Keeping a rough idea of what your system normally generates makes an unexplained drop much easier to spot. Our guide on why solar output drops goes into this in detail.

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Inverter Faults

The inverter is the most common source of faults — it’s the hardest-working part of the system. Because it converts your panels’ output every daylight hour, it ages faster than the panels. When it develops a fault, system output can drop sharply or stop altogether. Signs include error codes on the display, frequent dropouts, unusual buzzing or clicking, or constant loud fan noise in cool weather. Our guide on when to replace your solar inverter covers this more fully.

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Shading and Soiling

Not every drop in output is a hardware fault — sometimes it’s something blocking the light. New shading from a growing tree, a new building or even an aerial can cut output noticeably, because shading one part of a panel affects more than just that area. Soiling — dirt, bird droppings, moss or leaves — has a similar effect. Both are worth ruling out first, as they’re often the simplest to fix. Our guide to cleaning solar panels covers the soiling side.

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Panel-Level Faults

Less common, but worth knowing about, are faults within the panels themselves.

• • Micro-cracks: hairline fractures in the cells, sometimes from handling or weather.
  • Hot spots: localised overheating, often linked to shading or a faulty cell.
  • Delamination: the panel layers separating, showing as bubbling or milky patches.
  • Discolouration: yellow or brown staining, usually a sign of ageing materials.

Many of these are detected with specialist tools like thermal imaging, and some may be covered by your panel warranty. Our guide to solar panel warranties explains what’s typically covered.

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Wiring and Connection Faults

Faulty wiring or loose connections can quietly reduce output or, in some cases, trigger a safety shutdown. These can develop from weather, ageing, or sometimes birds nesting under panels and disturbing the cabling. If you ever see chewed cabling or signs of nesting, don’t touch it — turn to a professional, as the system carries high voltage. Bird-proofing can prevent the problem recurring; see our guide to bird-proofing solar panels.

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What to Do If You Spot a Fault

The single most important rule: don’t try to fix electrical faults yourself. Solar systems carry high DC voltage whenever there’s daylight — even on overcast days — so opening the inverter or working at the panels is genuinely dangerous. A sensible order of action:

1. 1. Check the easy things: note any inverter error code and look for obvious shading or soiling.
   2. Record what you see: the error message, and when the output dropped.
   3. Call a professional: a certified installer can diagnose safely and advise on repair or warranty.

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Why Choose a Professional Installer?

• • Safe diagnosis: the right tools and training for high-voltage systems.
  • Accurate fault-finding: pinpointing the cause rather than guessing.
  • Warranty support: help with claims where a fault is covered.
  • MCS certified installations: work to recognised standards.

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What Happens When You Request a Quote?

1. 1. Submit the form: tell us what you’ve noticed.
   2. We review: our team looks at your setup and the symptoms.
   3. Free consultation: we discuss your options with no obligation.
   4. Tailored quote: you receive a solution designed around your specific needs.

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Related Guides

• • Solar Panel Maintenance UK: Cleaning, Faults & Repairs
  • Why Has My Solar Output Dropped?
  • When Should You Replace Your Solar Inverter?
  • How to Clean Solar Panels (and Should You?)

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Frequently Asked Questions

What is the most common solar panel fault?

Inverter faults are the most common, because the inverter works every daylight hour and ages faster than the panels. They usually show up as error codes, frequent dropouts, or a sharp fall in output.

How do I know if my solar panels have a fault?

The clearest signs are a drop in output on your monitoring, an inverter error code, or visible marks such as cracks, discolouration or burn marks on a panel. Higher bills are often what homeowners notice first.

Can I fix a solar panel fault myself?

No. Solar systems carry high DC voltage whenever there’s daylight, so repairs are dangerous. You can check for obvious shading or soiling and note any error code, but diagnosis and repair should be left to a certified professional.

Is a sudden drop in output always a fault?

Not always. New shading, dirt or bird droppings can all reduce output without anything being broken. It’s worth ruling these out first, as they’re often the simplest to resolve before investigating hardware faults. Last updated: June 2026