Solar Panel Output: Winter vs Summer UK

Solar panels in the UK generate their lowest output in December, at roughly a quarter of what the same system produces in June, but they keep working every month of the year. Across the year a well-sited UK system produces around 20 to 30% of its peak summer output during the depths of winter, based on modelled figures from the European Commission’s PVGIS solar database. So if you have read on a forum that solar “doesn’t work in winter,” that is not what the data shows. Winter output is lower, not absent, and the financial case for solar is built around that seasonal pattern rather than in spite of it.

Solar output, sometimes called yield, is measured in kilowatt-hours (kWh) generated for each kilowatt-peak (kWp) of panels you install. That single measure lets you compare any system, in any month, on the same footing. This page uses it to show exactly how winter and summer generation compare in the UK, why the gap exists, and how a well-designed system keeps saving you money through the darker months.

We install solar, battery storage and EV chargers for homes and businesses across Warwickshire, the West Midlands and the surrounding counties, so the figures below reflect the kind of systems we fit and the weather our region actually gets.

Average UK Solar Panel Output by Month

The table below shows the average energy a south-facing UK system generates each month, expressed in kWh per kWp of installed panels. The figures are modelled from PVGIS, the European Commission’s satellite-based solar dataset (current version 5.3), averaged across UK postcodes. The Midlands sits close to this national average, at around 2.5 to 2.6 peak sun hours a day.

Source: PVGIS (European Commission Joint Research Centre), typical meteorological year, south-facing array. Annual total around 950 kWh per kWp. Exact monthly values vary by postcode, orientation and PVGIS version.

Read down the column and the seasonal shape is clear. May, June and July do the heavy lifting. December and January are the quiet months. The peak month (May, at 119 kWh per kWp) produces about four times the output of the lowest month (December, at 29 kWh per kWp). Taken together, the three winter months of December, January and February deliver a little under half of what an average month produces across the year.

What This Means for a Typical Home

For a typical 4 kWp system, the same size we fit on many Midlands homes (the UK average sits slightly higher, at around 4.5 kWp), those per-kWp figures work out at roughly 470 kWh in June and about 115 kWh in December, from an annual total near 3,800 kWh. At an electricity price of around 25p per unit, the power you generate and use yourself is worth something like £115 in June and close to £30 in December. That swing is the whole point of understanding seasonal output before you judge system size, export value or a battery quote: the summer surplus and the winter dip are two sides of the same year.

→ Work out the right size for your roof on our residential solar page.

How Well Do Solar Panels Work in Winter?

Solar panels work well in winter, generating meaningful power on every day of the year, because they run on daylight rather than direct sunshine. Photovoltaic cells respond to diffuse light, the scattered daylight that reaches the panel even under thick cloud, so a grey January morning still puts electricity into your home.

The output is lower for three plain reasons: the days are shorter, the sun sits lower in the sky, and there is more cloud. But “lower” is a long way from “nothing.” On a heavily overcast day, panels typically produce around 10 to 25% of their rated output, and on a brighter but cloudy day that can climb to 50 to 80%. Because most UK winter days are a mix of cloud and brighter spells rather than a total wash-out, real-world winter generation often lands above the gloomiest estimate.

A Midlands Example (illustrative)

Take a 4 kWp system with battery storage on a family home in the Midlands. On the PVGIS pattern above it would generate about 470 kWh in its best summer month and roughly 115 kWh in December — the same four-to-one seasonal swing shown in the table. A household like this can cover much of its winter daytime use straight from the roof, then lean on the battery and a smart tariff to fill the evening gap. Measured results from your own installer are the honest way to set expectations before you commit.

Curious how this applies to your roof? Get a free, no-obligation quote.

Factors Influencing Solar Output: Winter vs Summer

Three things drive the winter-to-summer gap in UK solar output: daylight hours, the angle of the sun, and cloud cover. Panel temperature plays a smaller, and slightly surprising, role. Here is how each one works.

Daylight Hours

Daylight hours are the single biggest factor in seasonal output. Around the summer solstice in June, much of the UK gets roughly 16 to 17 hours of daylight; around the winter solstice in December that drops to about 7 to 8 hours — in London the difference between the two is close to nine hours. Fewer hours of light means fewer hours of generation, which is why the summer and winter columns in the table are so far apart. There is nothing wrong with your panels in December; there is simply less day to work with.

The Sun’s Angle

The sun sits much lower in the sky in winter, so its light travels through more atmosphere and strikes your roof at a shallower angle. Both effects weaken the energy reaching the panels. This is also why roof pitch and orientation matter more than most people expect. A south-facing roof at around 35 degrees captures the most across the year, which is the reference case behind the figures on this page; an east- or west-facing roof typically gathers around 15 to 20% less. We assess pitch, orientation and shading on every property before we design a system, because those details change the numbers on your specific roof.

How Does Solar Panel Efficiency in the UK Change With the Seasons?

Solar panel efficiency in the UK actually improves slightly in winter, even though total output falls. Efficiency describes how well a panel converts the light it receives into electricity, and silicon panels lose roughly 0.3 to 0.4% of their rated power for every degree Celsius above 25 degrees. UK winter temperatures of around 2 to 8 degrees keep panels comfortably in their ideal range, so each hour of winter daylight is converted a little more effectively than a hot summer afternoon would be. The reason winter generation is still lower is simply that there are far fewer hours of light to convert. Efficiency and total output are two different measures, and they move in opposite directions across the seasons.

Regional Variation Across the UK

Output varies noticeably by region as well as by season. The South West, including Cornwall, Devon and Dorset, gets the highest solar irradiation in the country and milder winters, so systems there hold up better through December and January. Scotland and the far North sit lower, with cloudier skies that narrow the summer-to-winter gap but reduce the annual total. The Midlands falls between the two, close to the UK average. This shows up in payback too: Energy Saving Trust figures from July 2026 put payback at about 9 years in southern England, rising to roughly 12 years in central Scotland. A system designed for your exact postcode, roof and energy habits will always beat a national rule of thumb.

Solar payback across the UK (with Smart Export Guarantee payments)

Source: Energy Saving Trust, “Solar panels: costs, savings and benefits explained,” fuel prices as of July 2026 (England, Scotland, Wales). Payback is broadly similar whether you are home all day or out; the bigger levers are your export rate and how much you use yourself. The Midlands sits between the London and Manchester figures, so around 9 to 10 years is a realistic planning number.

Keeping Your Savings Steady Through Winter

You cannot move June’s sunshine into December, but you can make far better use of what winter does produce. Two things make the biggest difference: battery storage (which the Energy Saving Trust puts at around £5,000 to £8,000) and a smart, time-of-use tariff. Here is a practical checklist:

1. Add a battery. Store daytime generation and release it into the dark winter evenings when demand — and grid prices — peak.
2. Move to a time-of-use tariff. Top the battery up on cheap overnight rates on the greyest days, and export at premium rates where your tariff allows.
3. Shift heavy loads into daylight. Run the dishwasher, washing machine and EV charging while the panels are generating, so more of your output is used rather than exported.
4. Size for winter, not just summer. Building in headroom (see the 20% rule below) means the system still carries a useful share of load in December.
5. Keep panels clear and unshaded. Trim overhanging branches; light snow generally slides or melts off tilted panels within a day or two.