UK Solar Irradiance Lookup
Select your UK region to see estimated annual solar irradiance, monthly breakdown, optimal panel tilt, and expected generation for your system size. No API needed - all data is pre-loaded.
Solar irradiance varies significantly across the UK. Cornwall gets nearly 40% more sun than northern Scotland over a year. Use this lookup to estimate what your system will actually produce, not what the panel rating sticker says.
1. Select your region
Click your nearest region below. Each one has pre-loaded PVGIS irradiance data.
2. Enter your system size
Total installed panel capacity in kilowatts-peak.
About this data
The irradiance figures are based on PVGIS (Photovoltaic Geographical Information System) data from the European Commission's Joint Research Centre. Values represent the average annual solar irradiation on a south-facing surface at the optimal tilt angle for each region.
kWh/kWp means kilowatt-hours per year for each kilowatt of installed panel capacity. For example, if your region gets 1,000 kWh/kWp and you install a 4kWp system, you can expect about 4,000 kWh per year under ideal conditions.
Real-world output is typically 10-15% lower due to shading, soiling, inverter losses, and cable losses. The calculator shows both ideal and realistic estimates.
UK solar irradiance by region (reference table)
| Region | Annual kWh/kWp | Best month | Worst month | Optimal tilt (°) | Notes |
|---|
Tap any column to sort.
Common questions
What's a realistic annual output for a 4kW system in the UK?
Most of England produces 850-1,050 kWh/kWp per year. A 4kWp system in the Midlands at 950 kWh/kWp would generate about 3,800 kWh/year ideally, or around 3,200-3,400 kWh in the real world. That's roughly the annual electricity consumption of a typical 2-3 bedroom UK home.
Is solar worth it in Scotland?
Yes. While Scotland gets less sun (around 800-900 kWh/kWp), the longer summer days partially compensate. Plus, you still save on electricity at the same rate per kWh. The payback period is longer (12-15 years vs 8-10 in the south), but with panels lasting 25+ years, you still come out well ahead.
What's the best tilt angle for UK solar panels?
The optimal tilt for annual generation is roughly equal to your latitude (so 50-55° for most of the UK). However, if you have a shallow roof (30-40°), you'll still get 95%+ of the maximum. Steeper tilts favour winter generation; shallower tilts favour summer. A flat roof with panels at 10° tilt loses about 8-10% compared to optimal tilt.
How accurate is this data?
PVGIS data is the most widely used solar resource database in Europe. It's based on satellite measurements spanning 2005-2020. Accuracy is typically within ±5% for annual values. Individual years can vary by ±10-15% due to weather. The data here is a long-term average, not a guarantee for any given year.