Do Solar Panels Work in the UK?

UK vs Other Countries

The UK gets less sunshine than Spain or California, but solar panels still work well:

Spain

1,600 kWh per kW per year (50% more than UK)

UK (South East)

1,000-1,100 kWh per kW per year

UK (Scotland)

850-900 kWh per kW per year

Germany

900-1,000 kWh per kW per year (similar to UK)

Germany has more solar panels per capita than the UK despite similar irradiance. The difference is policy support, not sunshine.

Cloudy Day Performance

Solar panels work on cloudy days because they use diffuse irradiance (scattered daylight), not just direct sunlight.

On an overcast day, panels generate 10-25% of their peak output. On a bright overcast day (white clouds, no rain), they can hit 40-60% of peak.

Example: A 4 kW system with 4 kW peak output (midday sun) generates 400-1,000W on a cloudy day. That's enough to run a fridge, laptop, and lights.

Seasonal Variation

UK solar panels generate 3× more in summer than winter:

• June: 15-17% of annual generation (longest days)
• December: 2-3% of annual generation (shortest days)

This seasonal pattern matters because you use most electricity in winter (heating, lighting). Summer surplus gets exported to the grid at ~5.5p/kWh (SEG rate). A battery helps shift summer generation to winter evenings, but can't solve the seasonal mismatch entirely.

North-Facing Roofs

South-facing roofs generate most electricity, but east and west-facing roofs are still viable:

• South-facing: 100% of potential (baseline)
• South-east or south-west: 95% of potential
• East or west-facing: 75-85% of potential
• North-facing: 50-60% of potential (not recommended unless no other roof available)

East-facing panels generate more in the morning, west-facing more in the afternoon/evening. If your usage is higher in the evening, west-facing can be better than south despite lower total generation.

Shading Impact

Even partial shading (from trees, chimneys, or neighbouring buildings) can significantly reduce output:

• Shading 10% of a panel can reduce output by 30-50% (on string inverter systems)
• Micro-inverters reduce shading impact because each panel operates independently

If your roof has shading for 2+ hours per day year-round, solar may not be cost-effective. Get a professional shading analysis.

Real-World UK Examples

4 kW system, Midlands (950 kWh/kWp/year):
Annual generation: 3,800 kWh
Summer (Jun-Aug): 1,600 kWh
Winter (Dec-Feb): 500 kWh

4 kW system, South East (1,050 kWh/kWp/year):
Annual generation: 4,200 kWh
10% more than Midlands

4 kW system, Scotland (900 kWh/kWp/year):
Annual generation: 3,600 kWh
15% less than South East, but still viable

Do They Work in Winter?

Yes, but generation is low. A 4 kW system generates 40-60 kWh in December (1-2 kWh/day). That covers 10-15% of a typical household's winter usage.

Cold temperatures actually improve panel efficiency (panels work better at 15°C than 25°C). The issue is short days and low sun angle, not cold weather.