Red light on your solar inverter
A red fault light means the inverter has detected something outside its safe operating range and shut down. It is a protection mechanism — but it still needs diagnosing. The cause could be a momentary grid event that has already resolved, or an ongoing fault that will prevent generation until it's fixed.
The fault code is the starting point. Here's how to find it and what to do next.
A remote diagnostic session interprets the fault code in context — event log history, grid voltage data, system configuration — and gives you a clear cause and fix route.
Book a Remote Diagnostic — from £75 → GivEnergy fault codes →Safety: if you smell burning, see arcing or physical damage, isolate at the consumer unit immediately and do not restart.
What triggers a red fault light
Red fault lights cover a wide range of causes — from self-clearing grid events to faults needing hardware repair.
The grid voltage at your connection point has risen above the inverter's G98/G99 limits (typically around 253V in the UK). Common in areas with high solar density. The inverter disconnects to protect the grid. Often self-clears when grid voltage drops.
A leakage current detected between the DC solar circuit and earth — often caused by water ingress into a junction box, MC4 connector, or cable conduit. Common after heavy rain. Self-clears when dry but the ingress point must be sealed.
The inverter's AFCI system has detected an arc in the DC wiring. Common on SolarEdge and Enphase systems. Do not reset without investigating — a confirmed arc fault represents a fire risk and requires a qualified engineer to inspect the DC cabling.
The inverter cannot communicate with the battery BMS. The inverter shows a red light while the battery side is also faulted. See battery communication fault for the full diagnostic process.
One or more solar strings is producing a current outside the inverter's expected range — from a short circuit, damaged panel, or failed optimiser. The inverter trips the affected string or all strings.
The inverter has overheated — typically from poor ventilation, a blocked heat sink, or high ambient temperature combined with high output. The thermal protection trips the inverter. Usually self-clears once cooled. Check that airflow around the inverter is not blocked.
Arc fault codes require engineer attendance before reset. If your fault code indicates an arc fault (AFCI trip), do not attempt to reset the inverter. An arc in DC solar wiring is a fire hazard. The wiring must be inspected and the fault location identified by a qualified engineer before the system is restarted.
How to diagnose a red fault light
Start here — these steps apply to all inverter brands.
Note whether the red light is solid or flashing and at what rate. Check the inverter's own display for a fault code number. On most brands the display alternates between the fault code and other information — watch it for 30 seconds. Even "E01" or "F23" gives you something to work with.
Open your monitoring portal and look at the event log or fault history. The same fault code will be logged here, along with the exact time it triggered. Look at what happened immediately before — was there a grid event, a firmware update, heavy rain, high temperatures? Context helps identify the cause.
Use the fault code guide for your inverter brand to understand what the code means. GivEnergy, Growatt, Sunsynk, SolarEdge, and Solis all have different code numbering systems. See the brand pages and fault code guides linked below.
For grid faults, isolation faults, and temperature trips: turn off the inverter via its AC and DC isolation switches, wait 5 minutes, turn back on (AC first, then DC). See the safe shutdown guide for the correct sequence. If the fault clears and generation resumes, monitor the portal over the next 24 hours to confirm it doesn't recur.
Do not reset if the fault code indicates: arc fault, string short circuit, hardware failure, or battery BMS fault. Do not perform more than one reset without professional input.
A fault that returns immediately or within a few hours of resetting indicates an ongoing problem that won't resolve itself. Continuing to reset masks the underlying cause. Book a diagnostic to get a proper assessment before the fault worsens or causes secondary damage.
Fault code guides by brand
Frequently asked questions
A red light means the inverter has detected something outside its operating parameters and shut down as a protection measure. It is not necessarily a hardware failure — it could be a grid event, isolation fault, or overtemperature trip that will self-clear. The fault code on the display or in the portal event log tells you the specific cause.
A single controlled reset is reasonable for grid-related and transient faults. Turn off AC and DC isolation, wait 5 minutes, then restart. If the fault returns within a few hours, do not reset again — the underlying cause needs diagnosing. Never reset without checking the fault code first, and do not reset at all for arc fault codes.
Grid overvoltage is the most common cause — particularly in areas with high solar installation density where export from neighbouring systems pushes local grid voltage above the inverter's G98/G99 limits. Arc fault detection and isolation faults (earth leakage) are also very common.
Rain triggers isolation faults (earth leakage trips). Water ingress at a junction box, MC4 connector, or cable conduit creates leakage current between the DC circuit and earth. The inverter detects this and trips for safety. It often clears when the system dries out, but the ingress point needs to be found and sealed.
In most cases the inverter has shut itself down safely and is not in a dangerous state. Do not repeatedly reset. Arrange a diagnostic within a reasonable timeframe — not only because you are losing generation, but because some underlying faults can worsen if left unattended.
Need help interpreting your fault code?
A remote diagnostic reviews your full event log, grid voltage history, and system configuration to give you a definitive cause and a clear repair plan.