1. Check at the right time
Look during daylight, ideally around the middle of a reasonably bright day. Solar output is usually lower early in the morning, late in the afternoon and in winter. A reading of zero at night is normal.
2. Look at the inverter
Find the inverter display or its monitoring app. Look for current generation, today’s total and any warning or error code. Some inverters sleep when there is insufficient daylight. If you see a fault code, write it down and check the manufacturer’s instructions.
3. Make sure the app is connected
A blank graph does not always mean the panels have stopped. A changed Wi-Fi router, lost internet connection or disconnected monitoring device can prevent updates. Check whether the inverter itself reports generation before concluding the system has failed.
4. Compare like with like
Compare generation with a similar period in a previous year, allowing for weather and shading. A cloudy November day is not a fair comparison with a sunny June day. If you have the original installation estimate, use its monthly or annual figures as a rough reference, not a daily guarantee.
5. Check for new shade or visible dirt
From a safe position on the ground, look for new shade from growing trees, nearby buildings or other obstructions. Check for obvious debris or damage. Rain often cleans sloping panels, so routine paid cleaning is not always necessary. Never climb onto the roof to inspect or clean panels.
6. Check what the meter actually measures
Your electricity bill or smart-meter display usually shows electricity bought from or exported to the grid — not total solar generation. If you have a separate solar generation meter, its cumulative reading should generally increase over sunny periods. A monitoring or meter fault can make a working system appear inactive.
7. Know when to call for help
Seek professional advice if the inverter shows a persistent fault, generation stays at zero in suitable daylight, output has dropped substantially under comparable conditions, or there is visible damage. Burning smells, smoke, sparking, exposed wiring or signs of overheating need urgent attention: keep clear, do not touch the equipment and contact an appropriately qualified professional or emergency services as the situation requires.
Save this seven-point checklist
Do I need to pay for a solar inspection?
Not necessarily. If the only change is lower output in dull weather, start by monitoring it. If there is a persistent fault, unexplained loss of generation or damage, ask your original installer or a suitably qualified solar specialist for an explanation and written quotation. Check warranty coverage before agreeing to replacements.
Independent sources
- Energy Saving Trust — solar panels
- Energy Saving Trust — cleaning and maintenance
- Which? — common solar panel problems
- Electrical Safety First — solar panel safety
General guidance for UK homeowners. Equipment and fault procedures differ; always follow the manufacturer’s instructions and use qualified help for electrical work.