Inherited solar system not working
You've moved into a house with solar panels — but they're generating nothing, showing zero on the display, or throwing error codes. Some of these faults are simple to fix in five minutes. Others mean the previous owner left you an unresolved repair.
Work through the checks below to understand what you're dealing with before booking an engineer.
A significant number of 'not working' inherited systems are simply isolated — the previous owner turned off the isolation switches and didn't turn them back on. Check the inverter isolation switches and the solar circuit breaker before assuming a fault.
Monitoring access is a separate issue:
Get monitoring access on an inherited system →Why inherited solar systems aren't generating
In order of how commonly we see each cause on inherited systems.
The AC or DC isolation switch near the inverter is in the OFF position. This is the most fixable cause — takes 30 seconds to check and resolve. Check these first before anything else.
The solar circuit breaker in the consumer unit has tripped. Reset it (push to OFF then ON). If it holds, the system may recover. If it trips again immediately, there's a fault on the circuit that needs an electrician.
The inverter has detected a problem and stopped generating. The display will show a fault code or error number. Some codes are self-resolving (grid faults); others require engineer attendance (isolation faults, hardware errors). Note the exact code.
The system has been non-generating for an extended period — sometimes months or years — because the previous owner had no monitoring access and didn't notice. Dormant faults include failed optimisers, corroded connections, and degraded inverter components.
DC string fuses inside the inverter protect the panel circuits. If a fuse has blown, that string produces no output. Multiple blown fuses can take the whole system offline. Fuse replacement is a straightforward electrical job but requires qualified access to the inverter internals.
The inverter itself has failed — either a component failure or end-of-life. Inverters typically last 10–15 years. If the system is over 10 years old and showing no output with no obvious cause, inverter failure is a realistic possibility. May be covered by remaining warranty.
Step-by-step diagnostic
Work through these in order during daylight hours. Many cases are resolved at step 1 or 2.
Stand in front of the inverter during daylight hours — ideally on a sunny or partly cloudy day between 9am and 4pm. A generating system will show output in watts or kilowatts on the display. If the display is dark, the inverter has no power. If it shows zero, the inverter has power but is not generating. If it shows a fault code or error number, note it down exactly — this is your most important diagnostic data.
If the display is showing a generation figure above zero — even a small one — the inverter is working. Your issue is likely monitoring access, not generation.
Near the inverter — sometimes directly on the inverter casing, sometimes on the wall beside it — there will be isolation switches. Look for:
If either is OFF, turn it to ON and wait 2–3 minutes. The inverter will go through a startup cycle (this is normal — most inverters have a 30–300 second grid check before they begin generating).
Open the consumer unit (fuse board). Look for a circuit breaker labelled 'Solar', 'PV', 'Inverter', or with a sun or lightning bolt symbol. The switch should be fully in the ON position. If it is in the middle (tripped) position, push it fully to OFF and then firmly to ON. If it trips immediately on reset, stop — there is a fault on the circuit that needs an electrician to investigate. Do not keep resetting a breaker that is tripping.
If the inverter is powered but showing an error code, write it down exactly and search for it with your inverter brand name. Common inherited system fault codes:
For Growatt-specific error codes, see our Growatt fault code guide.
If steps 1–4 haven't resolved the issue, you have an underlying fault that needs professional diagnosis. Before booking an engineer visit, a remote diagnostic session can:
Systems that have been dormant for months or years
It is more common than people expect to inherit a system that hasn't been generating for a long time. Without monitoring access, the previous owner may not have known the system was inactive — or may have known and chose not to disclose it.
Check the inverter installation date on the label. The inverter label shows the manufacturing or installation date. If the system is over 8 years old, component failure becomes more likely — particularly for older string inverters with electrolytic capacitors that degrade over time. Newer hybrid inverters (under 5 years) are less likely to have hardware-level failures and more likely to have configuration or wiring issues.
Inspect the visible wiring and connections for obvious damage. Without opening any electrical panels yourself, look for visible signs of damage near the inverter — scorching, melted insulation, condensation or corrosion on visible connectors, or cables that appear to have been disturbed. Any of these indicate the system needs an electrician's assessment before it is operated.
Consider whether there may be a warranty or disclosure claim. If the system was non-generating at the point of sale and the previous owner was aware, this may constitute a failure to disclose a material defect. Contact your conveyancing solicitor with any evidence of extended non-generation (from monitoring data if you can access it) to assess whether a claim is viable. Inverter and panel warranties transfer with the property — check the remaining term.
Get a professional assessment before investing in repairs. On a dormant system, a remote diagnostic can confirm whether the issue is a configuration or data fault, or whether it requires physical engineer attendance. A full electrical inspection by a qualified solar engineer is advisable before spending money on component replacements — the scope of the issue needs to be understood first.
Brand guides and fault code resources
Available on-site across Yorkshire & beyond
Inherited a solar system that isn't working? We start with a remote diagnostic to identify the fault, then visit on-site for repairs if needed — across our full coverage area from Leeds to Sheffield, York, Hull, and beyond.
See all areas we cover →Frequently asked questions
Start with the basics during daylight: look at the inverter display — a generating system shows output in watts. Then check the DC and AC isolation switches near the inverter are both in the ON position. Finally, check the solar circuit breaker in the consumer unit hasn't tripped. These three checks take five minutes and resolve a significant number of non-generating inherited systems. If none of these are the cause, note any fault codes on the display and follow the diagnostic guide above.
Check the isolation switches near the inverter. There will be at least one DC isolator (for the solar panel cables) and one AC isolator (for the output to the consumer unit). These are typically red or grey rotary switches. If either is in the OFF or middle position, the system is isolated and will not generate. Turn both to ON during daylight hours and wait a few minutes for the inverter to complete its startup cycle.
Fault codes mean the inverter detected a problem and stopped generating as a safety measure. Common codes on inherited systems include grid fault errors (often self-resolving), isolation faults (ground fault on a panel or cable — needs engineer attention), and hardware errors (internal component failure). Write down the exact code and search it with your inverter brand name — or contact STS for interpretation. Do not ignore isolation fault codes.
If the inverter has power, isolation switches are on, the breaker is holding, but output is zero, likely causes include: failed DC string fuses inside the inverter, failed optimisers (on SolarEdge systems), a DC wiring fault between panels and inverter, or a failed inverter output stage. The panels looking clean from outside tells you very little about the electrical path — faults in this list are invisible from ground level. A remote diagnostic followed by a physical assessment is required to identify the specific cause.
Longer than you might expect — months or even years in some cases. Without monitoring access, a previous owner often has no way to know the system stopped generating. This is particularly common on older solar-only installs where the previous owner never set up monitoring. If you gain monitoring access and can see historical data, check when generation last showed a positive figure. The duration of dormancy affects both the repair scope and potential warranty or disclosure claims.
Possibly. Inverter warranties are typically 5–10 years from installation and transfer with the property. Panel warranties are typically 10–12 years for product faults and 25 years for performance guarantees — also transferable. If the system is within warranty, contact the manufacturer with the serial number and proof of ownership. If the fault developed during the previous owner's tenure and they were aware of it, there may also be a failure-to-disclose claim through your conveyancing solicitor.
Can't get the system generating after working through this?
For a new homeowner with a non-generating system, an independent solar inspection is the right starting point — a written report covering system condition, fault diagnosis, documentation, and a clear repair or warranty route.