Solar Inverter Fault & Red Light: What It Means
A red or amber light, a fault icon, or a warning message means your inverter has stopped or flagged a problem – so your system may not be generating right now. The good news: many faults clear on their own, and the most common one in Ireland (an isolation fault after heavy rain) often resolves once everything dries out. This guide walks through the likely causes in order, the safe checks you can do yourself, and when to call an electrician. If you are also seeing nothing at all on your meter, see our guide on solar panels not generating and our solar inverter brands overview.
Quick Answer
A red or amber light usually means the inverter has stopped because of a grid issue, over-temperature, or an isolation (insulation) fault. The most common cause in Ireland is moisture after heavy rain, which often clears once dry. First, note the exact fault code, open your monitoring app, and check for a tripped breaker. Never open the inverter or touch DC wiring.
Last updated June 2026
Fact-checked by John Rooney, Solar Energy Editor. Editorial policy
What does a red light or fault on a solar inverter mean?
A solid green light on an inverter means it is running normally. A red or amber light, a flashing light, or a fault icon on the screen means the inverter has either paused generation or detected a condition it is not happy with. Inverters are designed to be cautious: they will shut themselves down and wait rather than risk damage or an unsafe condition. Many of these shutdowns are temporary and the inverter will restart itself once conditions return to normal.
First, do this
Before anything else, write down or photograph the exact fault code or message shown on the inverter display, and note the colour and pattern of the warning light. The same red light can mean very different things on different brands, and your installer will fix it far faster if you can quote the precise code. Then open your monitoring app, which usually gives a plain-English description of the fault.
Safety: Solar DC wiring and inverters carry lethal voltage, even when the system looks 'off'. You may safely check things at app, breaker, and display level, but you must never open an inverter or touch DC wiring. For anything electrical, use a RECI / Safe Electric registered electrician in Ireland, or your original SEAI-registered installer while the system is under warranty.
Common causes of a solar inverter fault (most likely first)
These are the categories of fault you are most likely to be looking at, ordered roughly from most to least common in Irish homes. Your fault code or app message will usually point clearly to one of them.
1. Isolation / insulation resistance fault
The most common fault in Ireland. The inverter detects that the insulation resistance of the DC side has dropped, often because of moisture ingress in a connector or junction box after heavy rain. It frequently clears on its own once everything dries out. If it keeps coming back, a connector or seal usually needs attention from an installer.
2. Grid fault
The grid voltage or frequency is out of the permitted range, or there has been a grid outage. By design, the inverter stops exporting and waits, then restarts automatically once the grid is stable again. Common during local power cuts or when grid voltage runs high. Usually self-clears.
3. Over-temperature
The inverter has got too hot, often because it is in a poorly ventilated or very warm spot (a sunny attic or a tight airing cupboard). It throttles back or shuts down to protect itself and recovers once it cools. Recurring over-temperature usually means the location or airflow needs improving.
4. DC overvoltage or arc fault
The DC input voltage from the panels is too high, or the inverter has detected a possible arc in the DC wiring. These are protective trips. They are less common and should be looked at by your installer rather than repeatedly reset, as they can point to a wiring or array issue.
5. Earth (ground) fault
The inverter has detected current leaking to earth, which it treats as a safety condition and stops. This is an electrical fault that needs a registered electrician or your installer – it is not something to reset repeatedly. For a wider comparison of how different units report faults, see our inverter comparison.
Note: inverters installed in Ireland are EN 50549 compliant for grid connection, not the UK G98/G99 standard. The fault behaviour (waiting and restarting on grid issues) is part of that compliance.
Safe checks you can do yourself
Everything below is safe for a homeowner because it stays at app, breaker, and display level. None of it involves opening the inverter or touching wiring. Work through these in order before calling anyone.
1. Record the exact fault code or message
Photograph the inverter screen and note the light colour and flash pattern. This is the single most useful thing you can do and saves time on any callout.
2. Check your monitoring app
Most apps describe the fault in plain English and show whether generation has actually stopped or just dipped. Look at whether the fault appeared overnight, after rain, or during the hottest part of the day – that timing is a strong clue to the cause.
3. Check for a tripped breaker
Look at your consumer unit (fuse board) for an obvious tripped breaker or RCD linked to the solar system. If one has tripped, you can reset it once. If it trips again immediately, stop and call an electrician – do not keep resetting it.
4. Power-cycle once, if your manual permits
If your inverter manual allows it, you may switch the system off and on once using the AC isolator only: turn it off, wait a minute or two, then turn it back on. This often clears a transient grid or one-off fault. Do this once – never operate the DC isolator, and never keep cycling a fault that comes straight back.
5. If it followed heavy rain, give it time
Isolation faults after rain commonly clear themselves once the system dries out, sometimes within a day of dry or sunny weather. If it clears and stays clear, no further action is needed. If it keeps returning every time it rains, that points to moisture getting into a connector and needs an installer.
Do not: open the inverter casing, remove any covers, touch or unplug DC connectors, operate the DC isolator, or attempt any wiring work. The DC side carries lethal voltage in daylight and cannot be safely 'switched off' by a homeowner.
When to call an installer or electrician
If the safe checks above do not clear the fault, it is time to get a professional involved. In Ireland that means a RECI / Safe Electric registered electrician, or your original SEAI-registered installer if the system is still under warranty (which it usually is for the first few years on workmanship, and longer on the inverter itself).
Call straight away if
- A breaker or RCD trips again as soon as you reset it
- You see an earth fault or arc-fault code
- There is a burning smell, scorching, or visible damage near the inverter
- The inverter is buzzing loudly or unusually hot
- The same fault returns after one power-cycle
Use the right person
- Still under warranty? Contact your SEAI-registered installer first – a third party may void cover
- Out of warranty or installer gone? Use a RECI / Safe Electric registered electrician
- Have your inverter brand, model, and fault code ready before you call
- Ask whether the visit is covered or chargeable before booking
Persistent or repeating faults – especially isolation, earth, or arc faults – should always be diagnosed by a qualified person rather than reset over and over. Repeated resets can mask a genuine safety issue.
Irish context: rain, the grid, and your supplier
A few things are specific to running solar in Ireland and are worth understanding when you are diagnosing a fault.
Wet climate & isolation faults
Ireland's frequent, heavy rain makes moisture-related isolation faults one of the most common things we hear about. A one-off fault after a storm that clears when things dry is usually nothing to worry about. A fault that returns with every wet spell means water is getting somewhere it should not, and a connector or junction box needs resealing.
Grid voltage & ESB Networks
Grid faults are often caused by the local grid voltage running high, which trips the inverter off to protect itself. Your system is connected under ESB Networks rules via the NC6 notification your installer submitted. If you get persistent grid-voltage trips, your installer may need to raise it with ESB Networks.
Smart meter & export
Most Irish solar homes are on a smart meter under the National Smart Metering Programme (NSMP), which records your export for the Clean Export Guarantee (CEG) payment from your supplier. A fault that stops generation also stops export, so you may see it reflected in your supplier statements.
Who is responsible
The inverter and your wiring are yours (and your installer's under warranty). The grid up to your meter is ESB Networks. Export payments are between you and your electricity supplier. Knowing which is which helps you call the right party.
Solar Inverter Fault FAQ
Why is my solar inverter showing a red light?
A red or amber light means the inverter has stopped or flagged a problem. The most common causes are an isolation fault (moisture after rain), a grid fault (voltage or frequency out of range), or over-temperature. Note the exact fault code, check your monitoring app, and look for a tripped breaker before calling anyone.
What is an isolation fault on a solar inverter in Ireland?
An isolation (or insulation resistance) fault means the inverter has detected that the DC side's insulation has dropped, usually because moisture has got into a connector or junction box after heavy rain. In Ireland's wet climate this is common and often clears once the system dries out. If it keeps returning, a connector needs attention from your installer.
Can I reset my solar inverter myself?
If your manual permits, you may power-cycle the system once using the AC isolator only: switch it off, wait a minute or two, then switch it back on. Do this once. Never operate the DC isolator, never open the inverter, and never keep resetting a fault that returns immediately, as that can mask a genuine safety issue.
Is it safe to open my solar inverter to check it?
No. Solar DC wiring and inverters carry lethal voltage, even when the system appears off, and the DC side cannot be safely switched off by a homeowner. You may check things at app, breaker, and display level only. For anything electrical, use a RECI or Safe Electric registered electrician, or your SEAI-registered installer while under warranty.
My inverter fault cleared by itself. Should I still worry?
A one-off fault that clears on its own, especially an isolation fault after heavy rain or a grid fault during a power cut, is usually nothing to worry about. Keep an eye on your monitoring app for a week or two. If the same fault keeps coming back, record the code and contact your installer or a registered electrician.
Related Guides
Solar Troubleshooting
Diagnose common solar faults: generation, inverter, battery, export.
Solar Inverter Error Codes
Fault categories behind brand error codes and where to look.
Solar Panels Not Generating
No output? Inverter, isolator and breaker checks first.
Inverter Guide
Comparing string, micro, and hybrid inverters.
Sources
- ESB Networks — Microgeneration & connecting solar
- Safe Electric (RECI) — Find a registered electrician
- SEAI — Solar Electricity Grant & registered installers
Last updated 10 June 2026
John Rooney is the founder of Solar Info and has been covering the Irish solar energy market since 2023. He fact-checks all content against official SEAI data and maintains relationships with SEAI-registered installers across Ireland.
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