Helpful video reference. We use Electrician Life's UK tutorial "Solar PV system fault-finding guide" as the video reference here. The Electrician Life channel covers the systematic approach correctly, working from the monitoring app through to the inverter and isolators in the right order. Watch it before you start so you understand why the sequence matters.
1. Check the monitoring app or generation meter
Before touching anything, open the inverter monitoring app (SolarEdge, SMA Sunny Portal, SolarmanPV, GivEnergy, or whichever app your system uses) and look at the generation history. You want to know two things: when did output stop, and was it sudden or gradual?
A sudden drop to zero on a specific date and time points to an electrical fault or a grid event. A gradual decline over weeks suggests panel soiling, shading, or a slowly degrading component. Both are worth investigating, but the urgency and approach differ.
If you do not have a monitoring app, look at the generation meter (a small LCD counter usually fitted near the consumer unit or inverter). On a clear day, a healthy system should show a positive kWh reading by mid-morning.
2. Read the inverter display for fault codes
Walk to the inverter, which is usually fitted in the loft, garage, or on an internal wall near the consumer unit. Note the indicator lights and any text on the display. A green light and a positive power reading means the inverter is running. A red light, flashing amber, or a fault code means it has stopped and is telling you why.
Photograph the display. Then look the code up in the manual that came with your system (or search the manufacturer's support site for the code and your inverter model). Understanding the code before you call anyone means the conversation with the engineer is much shorter.
3. Check the AC isolator
The AC isolator is a rotary switch, usually red or grey, fitted to the wall between the inverter and the consumer unit. It disconnects the AC output side of the system. Check it is in the ON position. If it has been knocked to OFF, the inverter will show no output even though everything else is working fine. Turn it back on and wait a few minutes for the inverter to reconnect to the grid.
4. Check the consumer unit MCB or RCBO
Find the breaker labelled Solar or PV in your consumer unit. If it has tripped, reset it by pushing it firmly to OFF and then back to ON. If it trips again immediately, something on the circuit is causing a fault. In that case, leave it tripped and call an engineer.
5. Check the DC string isolator (look, do not touch)
The DC isolator is typically a red or black rotary switch fitted above the inverter. It sits between the roof cables and the inverter input. Look at it from a safe distance. Is the handle in the ON position? If someone has turned it off (during a roof job, for example) switching it back on will often restore output immediately.
Do not open the DC isolator enclosure or touch any DC wiring. The cables carry voltage directly from the panels and cannot be made safe without covering the panels or working in darkness. This is engineer territory.
6. Inspect for shading and soiling from the ground
From the garden or pavement (not the roof), look at the visible panels. A thick layer of bird droppings, leaves, or moss on even one panel in a string will reduce the whole string output significantly. In a series string, the weakest panel limits every panel above it. If the soiling is light and the panels are accessible from a ground-level wash, cleaning them may restore output. If they need anyone on the roof, use a professional.
Also look for new shading. A tree that was trimmed last year, a new aerial, or a neighbour's extension can cast shade that did not exist when the system was installed. Shade at the same time each afternoon will show as a consistent daily dip in the monitoring data.
7. Try a soft restart
If you have checked everything above and the inverter is still showing zero or a fault, try a soft restart: switch the AC isolator to OFF, wait 60 seconds, then switch it back to ON. The inverter will run through its startup sequence and reconnect to the grid. Most grid-fault shutdowns clear with a restart. If the same fault code appears immediately, the problem is persistent and needs an engineer.
When to call us
Richard covers fault-finding on solar PV systems across east Kent, including Sandwich, Deal, Dover, Folkestone and Canterbury. If the checks above have not resolved the issue, get in touch with the fault code and the generation history from the app. That information usually halves the time needed on site.
Solar system not generating in east Kent?
Richard diagnoses and repairs solar PV faults across the area. Bring your monitoring data and the inverter fault code and the job is usually quicker than expected.
Contact Richard