Solar Panel Problems: Faults, Repairs & When You Need a Professional
Published by AFTA Electrical · May 2026 · Solar Repairs
Most solar panel systems run for years without issues. When problems do occur, the symptoms are usually clear: generation has dropped, the inverter is showing an error code, the app shows zero output, or you can see visible damage to panels. This guide walks through the most common problems and what to do about them.
My Solar Generation Has Dropped — What's Wrong?
Generation can drop for several reasons, ranging from harmless to significant:
Seasonal variation: Output in December/January is typically 20–30% of peak summer output. Check you're comparing like-for-like months.
Soiling or bird fouling: Dirty panels can reduce output by 5–20%. Most systems need cleaning 1–2 times per year, more if you're near agricultural land or a roost.
Shading: A new structure, overgrown tree, or satellite dish that didn't exist when the system was installed can significantly reduce output, especially on string inverters without optimisers.
Inverter fault: Inverters typically display error codes when something's wrong. Check the display and note the code — this is the first thing a technician will ask for.
Failed or degraded panel: Individual panels can fail or degrade faster than expected. IV curve testing identifies underperforming panels.
Wiring fault: DC connections on the roof can corrode or come loose, particularly on older installations.
Common Inverter Error Codes
Inverters from different manufacturers use different codes, but some patterns are consistent:
Grid fault / grid voltage out of range: The inverter has disconnected due to grid voltage being outside permitted limits. Often self-resolves; persistent errors suggest a grid issue your DNO needs to investigate.
Insulation fault: A ground fault in the DC wiring. Must be investigated immediately — do not attempt to reset and ignore.
No grid / isolation: The inverter has lost AC connection. Check your consumer unit for a tripped breaker on the solar circuit.
Over-temperature: Inverter is overheating. Check ventilation around the unit.
What We Check During a Solar Fault-Finding Visit
Inverter error log and live readings
DC open-circuit voltage and short-circuit current per string
Thermal imaging of panels and connections (identifies hotspots, failed cells)
IV curve tracing per panel where needed
All DC and AC connection integrity checks
Earth continuity and insulation resistance
Installation documentation review (check original spec vs current output)
Beware of roof companies offering to "check your solar for free." Free solar inspections from non-electrically qualified contractors regularly result in expensive unnecessary recommendations. Have solar electrical faults diagnosed by a qualified, registered electrician.
Common causes include seasonal variation, soiling, shading, inverter faults, or panel degradation. Comparing your current output to the same month last year (via your monitoring app) is the first step.
Note the exact code displayed and check your inverter manual or manufacturer's website for its meaning. Some codes (like grid voltage faults) self-resolve. Others (insulation faults) require a professional visit. Call us with the code and we can advise.
Most domestic systems benefit from cleaning once or twice a year. Properties near agricultural land, busy roads, or bird roosts may need cleaning more frequently. A 10–15% output improvement from a clean is common.
We can diagnose most brands. Repair vs replacement depends on parts availability and inverter age. Inverters older than 10–12 years are often more cost-effectively replaced than repaired.