If your solar panels have suddenly stopped generating, or output has dropped significantly, there are a handful of common causes — and the inverter is often the one to look at first.
Common reasons for reduced output
Before assuming the worst, it’s worth checking the basics. Shading from a new tree, building work nearby, or accumulated debris on the panels can all drag output down noticeably. Bird droppings in particular cause localised shading that affects whole strings. Panel degradation is normal over time — a small percentage each year — but a sudden drop is different and worth investigating. Loose or corroded wiring can also disrupt output, especially after storms or temperature extremes.
Is it the inverter?
The inverter converts DC power from the panels into AC electricity your home can use. If it fails, the whole system stops generating — even if the panels themselves are fine. Most modern inverters have a display showing status and error codes, and a monitoring app that records output. A sudden flat line on the monitoring graph is a strong indicator that the inverter has faulted or tripped.
Common error codes you might see include grid fault (a problem with the mains supply), DC over-voltage (too much voltage coming from the panels), over-temperature (the inverter has overheated), and relay test fail (an internal component issue). Some of these clear themselves once the underlying condition resolves — a grid fault, for example, will often clear when the grid stabilises. Others require a service visit.
Check whether the inverter is properly ventilated. Inverters mounted in hot loft spaces or in direct sunlight can overheat and shut down temporarily. Moving it to a cooler location, or improving ventilation, sometimes resolves the issue without any other work.
What you can check yourself
If you’re comfortable doing it, gently cleaning the panels with a soft brush and water can make a difference if output has been gradually declining. Check the inverter display for any error messages and look up the code in the manual. You can also try turning the inverter off and back on following the procedure in your manual — this clears some faults. If the problem persists after these steps, or if you’re seeing error codes that point to internal faults, it’s time to call a qualified engineer.
Regular annual checks help catch small issues before they become bigger ones. It’s also worth informing your home insurer about your solar installation if you haven’t already, as some policies cover inverter failure.
If you’re experiencing issues and suspect the inverter, get in touch and we can diagnose the problem and advise on the options.
