How to Audit a Failed Solar System and Know Exactly What Went Wrong
When a solar system fails, the client usually blames the installer. But as a professional, your job is to diagnose the fault—not guess. A proper system audit helps you identify the exact cause of failure, avoid wrong assumptions, and restore the system quickly and correctly.
This guide walks you through a step-by-step framework to audit a failed solar installation and pinpoint the real problem.
1. Start With the Client Interview
Before touching anything, get information.
Ask the client:
• When did the problem start?
• What were they running at that moment?
• Was there any recent change (new appliances, wiring repairs, water leaks)?
• Has anyone else “touched” the system?
This initial history helps you avoid blind troubleshooting.
2. Perform a Visual Inspection
Walk through the installation carefully.
Look for:
• burnt wires
• undersized cables
• loose terminals
• water penetration
• melted MC4 connectors
• battery swelling
• inverter scorch marks
• cracked panel glass
• rusted or weak structures
If anything looks suspicious, document it immediately.
3. Measure Battery Voltage and Health
Batteries cause more than 60% of solar system failures.
Check:
• resting voltage
• voltage under load
• charging voltage from controller
• temperature
• swelling or leakage
• state of charge (SOC) reading vs actual voltage
Common battery-related failures include:
• battery deeply drained
• mismatched battery banks
• bad BMS in lithium batteries
• fake or low-quality batteries
4. Check the Inverter Status
The inverter is the command center, so inspect its behavior:
Verify:
• error codes
• overload warnings
• temperature alarms
• charging amps
• firmware or setting errors
• unstable AC output
Some problems may not be visible until you test with a stable load.
5. Test Solar Input From Panels
Use a multimeter to confirm if the panels are supplying correct power.
Check:
• open circuit voltage (Voc)
• short circuit current (Isc)
• panel-to-panel voltage (for series strings)
• shading at different times
• hot panels (heat reduces efficiency)
• bypass diode failure
• dirty surfaces reducing output
You may discover:
• wrong wiring (parallel instead of series or vice versa)
• mismatched panels
• fake panels
• one dead panel dragging the whole array
6. Inspect Charge Controller Functionality
A bad charge controller can destroy batteries.
Check:
• charging current
• battery type setting
• voltage reading accuracy
• temperature sensor connection
• overheating signs
• floating, bulk, and absorption stages
If readings on the controller don’t match your multimeter, something is wrong.
7. Verify Cable Size and Routing
Undersized or excessively long cables cause:
• voltage drop
• system overheating
• low charging efficiency
• inverter shutdown under load
Check for:
• 4 mm vs 6 mm vs 10 mm solar cables
• AC wiring gauge
• battery interconnect cables
• signs of heating or burning
8. Identify Load Problems
Some systems fail because the client is running the wrong appliances.
Audit the load:
• check wattage of each appliance
• check starting surge (for fridges, pumps, blenders)
• compare total load with system capacity
• identify hidden loads (chargers, extension boxes, fans, routers)
Sometimes the solar system is not the problem—load misuse is.
9. Check for Component Mismatch
A very common cause of system failure is mismatch between components.
Look for:
• panels too small for battery bank
• battery capacity too small for inverter size
• wrong charge controller rating
• mixing old and new batteries
• mixing lithium and gel batteries
• mixing different panel wattages or voltages
Mismatch = stress on components = early failure.
10. Identify Installation Errors
Sometimes, the system is failing because of the installer.
Watch out for:
• reverse polarity during wiring
• using single-core cables instead of solar twin-core
• loose breakers
• wrong MC4 polarity
• wrong grounding method
These errors often cause intermittent failure.
11. Document Your Findings
Take pictures, record voltages, write down errors.
Clients trust evidence.
Documentation helps you explain clearly what went wrong and what needs to be replaced.
12. Provide a Clear Conclusion
After your audit, summarise:
• root cause of the failure
• components that must be replaced
• preventive recommendations
• corrected load limit for the client
This gives you authority and shows professionalism.
