Solar Panels in British Winters: Real Yield Data 2026

The UK Solar Resource: More Than You Think

The UK averages approximately 900–1,100 kWh of solar energy per square metre per year (kWh/m²/yr), compared with 1,800+ in southern Europe. That figure sounds discouraging, but it is important context: every kWh a UK solar panel generates displaces an imported unit worth 25–30p. Even modest winter generation has real financial value.

The UK's solar resource is also more evenly distributed through the year than many assume. Winter generation is lower, but the country sees more diffuse (scattered) light than total darkness — and modern solar panels are surprisingly effective in diffuse conditions.

Monthly Yield Data: Real UK Figures

The following data comes from PVGIS (EU's photovoltaic geographical information system) modelling for a 4kWp south-facing system at 35° tilt across three UK locations.

For a 4kWp system. Actual output varies with shading, roof orientation, and temperature.

Why Panels Still Work in Winter

Diffuse light generation

Solar panels generate electricity from photons, not heat. On an overcast day, diffuse radiation still reaches the panel — typically at 15–30% of clear-sky intensity. A panel that generates 3kWh on a clear August day might generate 0.6–0.9kWh on a grey January day. That is still meaningful.

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Temperature effect

Solar cells are actually more electrically efficient at lower temperatures. A panel rated at 25°C Standard Test Conditions may perform 2–4% better in the cold UK air than its nameplate suggests. This partially compensates for reduced irradiance.

Longer daylight hours offset

In June, London has 16+ hours of daylight. In December, it has under 8 hours. This daylight difference explains a significant part of the summer/winter gap — it is not purely about cloud cover.

Panel Technologies in Low Light

Not all solar panels perform equally in diffuse UK conditions. Key differences:

• Monocrystalline PERC panels (now standard from most manufacturers including Canadian Solar, Jinko, and Q Cells) perform well in low-light conditions — better than older polycrystalline panels.
• HJT (heterojunction) panels such as those from REC and Panasonic have superior low-light performance, with lab data showing 2–5% better energy yield per watt-peak in diffuse conditions.
• Microinverters (Enphase) and optimised string inverters (SolarEdge) can improve winter performance by 8–15% in shaded installations, as each panel operates independently.

Maximising Winter Output

Panel tilt angle

For maximum annual yield in the UK, 30–35° is standard. However, steeper tilts (40–45°) capture more winter irradiance when the sun is lower in the sky. If you are primarily targeting winter self-consumption (e.g., to cover heat pump loads), ask your installer about a steeper pitch.

Panel orientation

South-facing arrays capture the most annual energy. East-west split arrays capture about 85% of south-facing annual yield but distribute generation more evenly across the day — useful for households where morning and evening consumption is high.

Keep panels clean

Winter moss, bird droppings, and general grime reduce output year-round but the impact is proportionally larger in winter when every kWh counts. An annual clean in October before the low-irradiance months is worthwhile. Most installers offer this service for £50–£120.

Winter vs. Summer: Financial Perspective

In summer, UK households often generate more than they consume and export the surplus. In winter, generation may only cover 20–40% of daily electricity use, but every unit generated is worth 25–30p (the avoided import price). Winter kilowatt-hours are not worthless — they are just fewer.

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