Enter your system details (size, location, orientation, age) and your monthly generation readings from your inverter display or monitoring app. The tracker compares your actual output against expected generation for your specific setup and region, calculating a performance ratio. You’ll see whether your system is performing well or potentially has issues that need investigating.
Solar generation in the UK varies significantly by location, orientation, and time of year. Here’s what you should expect from a well-performing system:
Solar generation in the UK follows a predictable seasonal pattern. Understanding this helps you identify whether a “low” month is actually normal or a sign of problems:
Typical monthly distribution of annual solar generation in the UK
Key seasonal insights: May-August accounts for nearly 50% of annual generation. December and January together produce only about 6%. A system that seems to “barely work” in winter may be performing perfectly normally — check summer months to assess true performance.
Even partial shading on one panel can significantly reduce output for string inverter systems. Common culprits include tree growth (especially deciduous trees that shade in summer when you need generation most), new buildings, satellite dishes, TV aerials, and chimney shadows. Check panels at different times of day and in different seasons.
Bird droppings, pollen, dust, and general grime can reduce output by 5-25%. UK rainfall usually keeps panels reasonably clean, but panels at low angles or in areas with high pollution may need occasional cleaning. Heavy bird activity (near trees or with pigeons nesting underneath) is a common cause of localised soiling.
The inverter is the most likely component to fail, especially after 10-15 years. Signs include error codes on the display, the system shutting down during peak generation, or inconsistent output. Check for red warning lights, error messages, or unusual noises. Inverter issues often cause complete or near-complete loss of generation.
All solar panels degrade over time — typically 0.5% per year. A 10-year-old system should still produce about 95% of its original output. If degradation seems faster than this, it could indicate manufacturing defects, damage, or poor quality panels. Check warranty terms — most panels are guaranteed to produce 80%+ at year 25.
Loose connections, damaged cables, or corroded connectors can reduce output or cause intermittent problems. Rodents sometimes damage cables in loft spaces. DC isolator switches can also fail. These issues require professional inspection and repair — never attempt to work on solar wiring yourself.
Most inverters have a display showing daily, monthly, and total generation. Many modern systems also have smartphone apps (SolarEdge, Enphase, GivEnergy, etc.) or web portals where you can view detailed generation data. If you have a smart meter, you may also be able to see export data through your energy supplier’s app.
Yes, this is completely normal for the UK. December and January each typically produce only about 3% of annual generation due to short days, low sun angle, and frequent cloud cover. A 4kWp system might generate only 80-120 kWh in December vs 450-500 kWh in June. Judge your system’s performance primarily on summer months.
UK rainfall usually keeps panels reasonably clean. However, cleaning may be worthwhile if you notice heavy bird droppings, live near a dusty road, or have panels at a low angle where dirt accumulates. Use plain water and a soft brush or cloth — avoid pressure washers and abrasive materials. Professional cleaning typically costs £50-100 and may be worth it every 1-2 years for heavily soiled systems.
South-facing panels at around 35° tilt are optimal for the UK. South-east or south-west facing panels typically produce about 95% of optimal output. East or west-facing panels produce around 85%. Even north-facing panels can work, though they’ll produce only about 60% of a south-facing system. The tracker adjusts expected generation based on your orientation.
Contact your installer or a solar maintenance company if: your inverter shows error codes or warning lights, generation has dropped suddenly (not gradually), your performance ratio is consistently below 75%, you can see visible damage to panels or wiring, or the system has stopped working entirely. Most issues are straightforward to diagnose with the right equipment.
A well-maintained solar system should perform at 85-100% of expected output for its age and location. Small variations are normal due to weather differences between years, but consistent underperformance of more than 15% warrants investigation. Track your generation monthly, keep panels reasonably clean, and address any shading issues promptly. Most solar systems require very little maintenance but benefit from occasional monitoring to catch problems early.