M&E Contrax Resources
Common Solar Panel Problems
Resource Highlights:
The most common causes of low output are inverter faults, monitoring issues, shading changes, and wiring or connection problems.
Not all “problems” are faults, seasonal variation and weather changes are normal.
If output drops suddenly or monitoring stops reporting, it is worth investigating quickly.
What causes low generation, how to spot issues, and what to do next
Solar PV is generally reliable and low maintenance, but like any electrical system, problems can happen. The key is knowing what “normal” looks like, recognising the early warning signs, and getting issues checked quickly so you do not lose months of generation.
This guide covers the most common solar panel problems we see in the UK, what usually causes them, and the practical next steps.
First check, is it actually a problem?
Before assuming something is wrong, check these basics:
Seasonal variation
Solar output is naturally higher in summer and lower in winter. Short days and a lower sun angle reduce generation, even on bright winter days.
Weather variation
Cloud cover, haze, and rain can reduce output significantly compared to a clear day. Compare performance on days with similar weather.
Your usage pattern
If you have a battery or smart tariff setup, you may notice different import/export behaviour day to day. That does not always mean the system is underperforming.
If you are seeing a sudden, clear drop compared with similar days, or your monitoring has stopped reporting entirely, it is likely worth checking further.
Problem 1 | Inverter fault or failure
The inverter is one of the most important components in a solar system and is a common cause of performance issues.
Signs
Generation drops to zero on bright days
Inverter shows a warning light or fault code
Output is intermittent
Monitoring shows flat lines or repeated dropouts
What to do
Check the inverter display for warning lights or error messages
Check your monitoring app for fault alerts
Contact a qualified installer or engineer, do not attempt DIY electrical checks
Problem 2 | Monitoring has stopped working
Sometimes the solar system is generating normally, but the monitoring has lost connection.
Signs
App shows “no data” or stopped updating
Inverter appears normal but app is blank
Data freezes on a specific date
Causes
WiFi changes or router replacement
Weak signal at inverter location
App or platform outages
Data logger or monitoring gateway issues
What to do
Check your WiFi and whether the inverter is still connected
Restart the router if needed
If the issue persists, ask your installer to check the monitoring setup
Monitoring problems matter because they can hide real performance issues.
Problem 3 | Shading changes over time
Even if a system was designed properly, shading can change year on year.
Signs
Gradual drop in output year on year
Strong morning or late afternoon dips
Certain seasons perform worse than expected
Causes
Tree growth
New extensions, dormers, or roof features
Neighbouring building changes
What to do
Compare output year on year for the same months
Visually check if shading has increased
If shading has changed significantly, a system review can confirm whether layout changes, optimisers, or other adjustments are worth considering
Problem 4 | Debris, dirt or bird mess
Most systems do not need regular cleaning, but heavy build up can reduce output.
Signs
Output lower than expected during good weather
Visible debris on panels, especially near trees
Bird mess concentrated on a section of the array
Causes
Low pitch roofs where dirt does not wash away easily
Trees or sheltered roof areas
Bird activity
What to do
Never climb onto the roof yourself
If build up is visible and output is down, consider professional cleaning
If build up is visible and output is down, consider professional cleaning
Most people get the best value by conditioning the rooms they actually use, rather than trying to cool or heat the whole house all at once.
Problem 5 | Electrical connection issues
Loose connections, damaged cabling, or isolation issues can reduce generation or cause intermittent faults.
Signs
Intermittent generation
Fault codes related to strings or voltage
Burning smell or visible damage near equipment (rare but urgent)
Causes
Natural wear over time
Poor installation workmanship
Rodent damage in some settings
Weather exposure on external cabling or junction points
What to do
Treat anything electrical as a professional job
Contact your installer immediately if you suspect damage or overheating
Keep the area safe and avoid touching equipment
Problem 6 | Panel damage
Solar panels are robust, but extreme weather or impact damage can occur.
Signs
Visible cracks or shattered glass
Water ingress signs
Sudden unexplained output drops after a storm
Causes
Storm debris
Rare manufacturing faults
Physical impact
What to do
Do not attempt to inspect up close on the roof
Contact an installer to assess safely
Panels may be covered under warranty depending on the cause and product
Problem 7 | DC isolator or protection issues
Solar systems include isolators and protective devices. If these trip or fail, generation can stop or become inconsistent.
Signs
Sudden drop to zero
Inverter fault messages
Generation only returns after reset (but fails again)
What to do
Do not repeatedly reset without understanding the cause
Ask your installer to check protection devices and isolators properly
Simple overview
If you want the simplest approach, follow this order:
Check your monitoring against a similar weather day
Look for sudden changes, flat lines, or missing data
Check the inverter display for warning lights or fault messages
Visually check from ground level for obvious debris or damage
Consider whether shading has changed over time
If the issue persists, book a professional system check rather than leaving it
This avoids the most common problem, losing weeks or months of generation because a small issue was not spotted early.
Frequently Asked Questions
Compare generation on similar weather days and track monthly totals. A sudden drop, flat line, or repeated faults is a sign to investigate.
Days are shorter and the sun is lower in the sky, so lower generation is normal in winter.
Yes. Monitoring can fail even if the system is generating. That is why inverter checks and occasional performance review matter.
Inverter or monitoring related issues are among the most common causes of reported problems.
Download a copy of this resource
Our resources are available for you to download, enter your details below and we will e-mail you a download link.
