Solar Panels Not Working? Your Step-by-Step Diagnosis Guide
Generation dropped to zero, a red light on the inverter, or a meter reading nothing? Here’s how to find out what’s wrong — and get an engineer round to fix it.
The short answer
If your solar panels have stopped working, the most likely culprit is the inverter (the working heart of the system, and the part most likely to fault) — so check it first for a red/amber light or an error code. Other common causes: a tripped AC isolator or breaker, a grid/supply issue, or a meter/monitoring fault that only makes it look like generation has stopped.
What’s safe to check yourself is limited — isolators, the app, the error code, one power-cycle. Anything involving the roof, DC wiring, or a persistent fault needs an MCS-certified engineer. The good news: a diagnosis visit is usually £80–£150 (often credited against the repair), and even if your original installer has ceased trading, any qualified engineer can help. Free quotes get one round to you.
What this guide covers
Solar panels stopping is unsettling — you’re watching a system that should be saving you money sit dead, and the bills creep back up. The reassuring news is that most causes are fixable and often simple: frequently it’s the inverter (repairable or replaceable), a switch that’s tripped, or even just the monitoring playing up while the system quietly works fine. This guide walks you through finding out what’s wrong, tells you what’s safe to check yourself, and — for anything beyond the basics — how to get a qualified engineer round to diagnose and fix it.
First: is it actually broken?
Before assuming a fault, rule out the false alarms — a good share of “not working” turns out to be neither broken nor serious:
- Is it just the app or monitoring? A dropped WiFi dongle shows “offline” or zero in the app while the system generates perfectly. Check the inverter itself, not just the app.
- Is it a dull day or winter? Panels generate less in cloud and winter — low output on a grey day is normal, not a fault. Reduced generation isn’t the same as zero.
- Is it actually daylight generation you’re checking? Inverters power down at night and in near-dark — a blank display at dusk is normal.
- Has the grid just wobbled? A momentary supply event can trip the inverter, which then rides it out and restarts.
If you’ve ruled these out and there’s genuinely zero generation in decent daylight, or a fault light/code on the inverter, then yes — something needs attention. Here’s how to narrow it down.
The step-by-step checks
| Step | Check | What it tells you |
|---|---|---|
| 1 | Inverter status light | Green = OK · Red/amber = fault |
| 2 | Inverter display / app for an error code | Note it — it points to the cause |
| 3 | Is it generating (kW) in daylight? | Zero in good light = real fault |
| 4 | AC isolator switch (near inverter/meter) | Knocked off = easy fix |
| 5 | Consumer unit / fuse box breakers | Tripped breaker = reset once |
| 6 | Generation meter counting up? | Stuck meter but inverter OK = meter fault |
Work through these in order and you’ll usually locate the problem area — most often it’s step 1–2 (the inverter) or step 4 (a tripped isolator). Whatever you find, note the exact error code and photograph the inverter screen: it’s invaluable for an engineer and often lets them arrive with the right part.
The common causes, ranked
- Inverter fault (most common): the inverter is the hardest-working component and the one most likely to fail over a system’s life. A red light or error code points here. Sometimes a firmware glitch (fixable), sometimes a genuine failure needing repair or replacement. Inverters typically last 10–15 years, so an older system dying is often the inverter.
- Tripped isolator or breaker: the AC isolator or a consumer-unit breaker has tripped (a power surge, a fault elsewhere). Sometimes a simple reset; if it trips again immediately, there’s an underlying fault — stop and call an engineer.
- Grid / supply issue: voltage or frequency out of range, or a local supply problem, shuts the inverter down until it stabilises. Often not your equipment’s fault.
- Meter / monitoring fault: the generation meter or monitoring has failed while the panels still generate — looks like “not working” but isn’t (see below).
- Shading, failed panel or wiring: less common as a sudden total stop, but a failed panel, connector or wiring damage (including bird or rodent damage) can cut or crash output. Needs an engineer to trace.
“My generation meter shows zero”
A common and confusing one, worth its own note. A generation meter reading zero means one of two very different things:
- The system has genuinely stopped — inverter fault, tripped isolator or supply issue. Here the inverter will usually also show a fault or zero.
- Only the meter (or its connection) has failed — the panels are still generating fine, but the meter isn’t recording it. Here the inverter shows normal status and generation during daylight.
So the quick test: check the inverter. If it’s showing normal status and producing kW in daylight, your panels are working and the fault is the meter — annoying (it affects your generation records and any payments tied to them) but not a system failure. If the inverter is also faulted or zero, the problem is system-wide. Either way, a meter or generation-recording fault is worth fixing to protect your export/generation income.
What’s safe to do yourself — and what isn’t
Stick to these; leave the rest to an engineer
Safe: checking the inverter’s status light and error code, confirming the AC isolator is on, resetting a tripped breaker once, checking whether it’s just the app offline, and a single inverter power-cycle if your manual permits. Not safe, ever: going on the roof, opening the inverter, touching or inspecting DC cabling (live and potentially lethal whenever there’s daylight), or repeatedly resetting a fault that keeps returning. If a reset doesn’t hold, or you’re dealing with anything beyond a switch and a code, that’s the point to call a professional — not to keep trying. No saving is worth a fall or a shock, and the safety rules here are non-negotiable.
Getting an engineer round to diagnose it
For anything past the safe basics, you want an MCS-certified engineer to diagnose the system properly. Here’s how it works and what to expect:
- Cost: a diagnosis/callout visit is typically £80–£150, and it’s usually credited against the repair if you go ahead — so it’s rarely money wasted.
- Original installer gone? Very common — many solar firms have ceased trading in recent years. You’re not stuck: any MCS-certified engineer can diagnose and repair your system, whoever installed it.
- Under warranty? If your system or inverter is still in warranty and the installer is trading, start with them — but if they’ve gone, an independent engineer can still help (and advise on any manufacturer warranty that survives).
- Come prepared: have your error code, a photo of the inverter screen, and the system’s age/install date ready — it speeds diagnosis and can get the right part on the first visit.
The simplest route is to get a couple of free, no-obligation quotes from vetted engineers, compare them, and pick one — rather than ringing round yourself. That’s exactly what we help with.
Not working: do’s & don’ts
✓ Do
- Check the inverter light & note any error code
- Confirm the AC isolator & breakers are on
- Photograph the inverter screen
- Check if it’s just the app/monitoring offline
- Reset a tripped breaker once
- Get an engineer for anything persistent
✗ Don’t
- Go on the roof to investigate
- Open the inverter or touch DC wiring
- Repeatedly reset a recurring fault
- Assume zero output on a grey day = fault
- Panic if the original installer has gone
- Ignore a meter fault (it affects your income)
Frequently asked questions
Why have my solar panels stopped working?
Most often the inverter (check for a red light or error code), a tripped isolator or breaker, a grid/supply issue, or a meter fault that only makes it look like generation stopped. Less commonly shading, a failed panel or wiring damage. Check the inverter first.
How do I know if they’re working?
Check the inverter’s status light (green vs red), the display/app showing generation in kW during daylight, and the generation meter counting up. Normal status and daylight generation = working. Zero in good light, a red light, or an error code = a fault.
Can I fix it myself?
Only the basics — check isolators and breakers, note the error code, see if it’s just the app, one power-cycle if the manual allows. Anything involving the roof, DC wiring, opening the inverter, or repeat-resetting a fault is an engineer’s job. Solar DC is live and dangerous.
Who do I call?
An MCS-certified engineer. If your installer is still trading (and you’re under warranty), start there; if they’ve gone — common — any MCS engineer can help. Diagnosis is usually £80–£150, often credited against the repair. We can get you free quotes from vetted engineers.
Why does my generation meter show zero?
Either the system genuinely stopped (inverter/isolator/supply — the inverter will also show a fault) or just the meter failed while panels still generate (inverter shows normal). Check the inverter to tell which. A meter-only fault still needs fixing as it affects your generation/export records.
Do they stop in cloudy or winter weather?
No — they generate less, not nothing, from daylight rather than direct sun. Low output on a dull day is normal; zero output in reasonable daylight is not and indicates a fault. Don’t mistake seasonal variation for a breakdown.
Check the inverter first — then get an engineer round
The bottom line: Most “not working” solar comes down to the inverter, a tripped switch, or a monitoring glitch — check those first, safely. For anything genuine, don’t wrestle with it: a £80–£150 diagnosis (usually credited against the repair) gets a qualified engineer to find and fix the fault, whoever installed your system.
Get my free diagnosis quote →The verdict
Solar panels that have stopped are usually fixable, and often the cause is simpler than you fear — most commonly the inverter, a tripped isolator, or a monitoring fault that only makes it look like the system’s dead. Run the safe checks first: inverter light, error code, isolators, and whether it’s genuinely zero generation or just the app.
For anything beyond that, get a qualified engineer round rather than risking the roof or the wiring yourself. A diagnosis visit is £80–£150, usually credited against the repair, and even if the company that installed your panels has long gone, any MCS-certified engineer can pick it up. The quickest way to get one to your door is a couple of free, no-obligation quotes — compare and choose, and get your system earning again.
Get your free diagnosis quotes from MCS-certified engineers →
Important
Going Solar UK is an introduction service, not an installer or electrical contractor. This guide is general information, not electrical or safety advice: solar DC wiring is live and potentially lethal, and diagnosis or repair should be carried out by a qualified, MCS-certified engineer. Never go on your roof, open an inverter, or touch DC cabling yourself. Diagnosis costs are indicative 2026 figures and vary. If you smell burning or see scorching or smoke, switch off at the AC isolator if safe and seek urgent professional help.
We may receive a commission when we introduce you to an installer, at no cost to you. Any contract for work is directly between you and the installer.