Introduction
The sun hours table is an essential tool when planning or evaluating a solar PV installation. Whether you're assessing a roof, plot of land, or commercial building, you need a clear understanding of how many hours of sunlight your region actually receives. Sun hours directly influence the potential output of a solar PV system—your annual energy yield depends heavily on them.
This guide explains how sun hours vary across the UK, how they affect the performance of a solar PV system, and why some regions can generate far more solar electricity than others.
What Are Sun Hours – and Why Are They So Important?
Sun hours are meteorological measurements indicating how many hours per year sunlight reaches the Earth with a minimum level of intensity. They serve as a key indicator for assessing the solar potential of a region.
Why sun hours matter:
- They determine the theoretical PV energy yield (kWh/kWp).
- More sun hours = higher generation.
- They guide decisions on panel types and system size.
- They heavily influence financial returns and payback time.
No matter how large a PV system is, its output is always limited by available sunlight.
Sun Hours Table UK 2025 – Regional Overview
The UK has significant regional differences in annual sun hours — a factor often underestimated by homeowners. While the South East and South West receive over 1,600 sun hours per year, northern Scotland may see fewer than 1,100 hours.
Here is a clear, structured table similar to your German example:
| Region | Sun Zone | Sun Hours / Year | Expected PV Yield (kWh/kWp) |
| South East England | 🟩 Very High | 1,600–1,700 | 1,050–1,200 |
| South West England | 🟩 Very High | 1,500–1,650 | 1,000–1,150 |
| East of England | 🟨 Medium-High | 1,450–1,550 | 950–1,050 |
| London | 🟨 Medium-High | 1,450–1,550 | 950–1,050 |
| Midlands | 🟧 Medium | 1,300–1,450 | 900–1,000 |
| North West England | 🟧 Medium-Low | 1,200–1,350 | 850-950 |
| Northern Ireland | 🟧 Medium-Low | 1,200–1,350 | 850-950 |
| Scotland (Central Belt) | 🟥 Low | 1,100–1,250 | 800-900 |
| Scottish Highlands | 🟥 Low | 1,100–1,250 | 800-900 |
How Do Sun Hours Influence Solar PV Output?
Sun hours determine how much solar energy your panels can convert over the year. A region with more sunlight will naturally generate more electricity.
Relationship between sun hours & PV performance:
- Higher sun hours → greater annual generation
- Lower sun hours → larger system size needed to achieve the same output
- Additional influencing factors include:
- temperature
- module efficiency
- shading
- tilt angle
- roof orientation
A good UK rule of thumb:
1,000 sun hours produce roughly 1,000 kWh per kWp annually under ideal conditions.
Most UK installations deliver 850–1,200 kWh/kWp per year, depending on region and setup.
Other Factors Influencing UK PV Potential
Sun hours alone don’t determine solar performance. Several additional factors play an important role:
1. Roof Orientation
- South-facing is optimal
- East-west can still generate 80–90% of south-facing output
2. Roof Tilt
A tilt of 30–40° is ideal for UK latitudes.
3. Shading
Nearby trees, buildings or chimneys reduce output significantly.
4. Module Type
Monocrystalline panels provide the highest yields.
5. Temperature
Cool weather often increases efficiency — meaning northern regions sometimes perform better than expected.
Common Misunderstandings About Sun Hours
Many homeowners misunderstand how sun hours work. Here are typical misconceptions:
❌ 1. "Sun hours equal direct sunlight hitting my roof."
Not exactly. Sun hours measure sunlight intensity, not how optimally your roof is positioned.
❌ 2. "Clear skies guarantee high PV output."
Cool, bright days often outperform hot days because panels work best at lower temperatures.
❌ 3. "Winter sunshine makes a big difference."
Winter sunlight is weak and has a low angle. Most UK solar production occurs between March and October.
Climate Change – Will Sun Hours in the UK Increase?
Early data suggests:
- Southern England: Slight increase in summer sun hours
- Scotland & Northern Ireland: Gradual rise in clear days
- Western UK: High variability due to Atlantic weather systems
While long-term forecasts are not definitive, the general trend suggests a modest improvement in PV potential — assuming extreme cloud cover does not increase.
Conclusion
The sun hours table highlights how strongly solar radiation varies across the UK — and how these differences influence PV system performance. While southern regions such as the South East and South West enjoy up to 1,700 sun hours, even areas with fewer hours can still achieve excellent solar yields when systems are well designed.
Beyond sun hours, factors like roof pitch, shading, temperature and panel type play a crucial role. With proper planning, a solar PV installation can be highly effective and financially beneficial across almost the entire UK.
Understanding your region’s sun hours gives you the knowledge needed to maximise your solar investment and make informed decisions for a future powered by clean energy.
