Facts last checked 17 September 2026
The short answer
Yes, solar panels work in winter, because they run on daylight, not warmth, and cold does them no harm. What changes is how much light there is. On EU JRC PVGIS modelling, a 4 kWp south-facing system in London averages about 144 kWh in December (4.7 kWh a day) against 493 kWh in June (16.4 kWh a day), and December to February together produce only about 13% of the year's output. Judge solar on the whole year, and expect summer to do most of the work.
Why do solar panels still work when it is cold and grey?
A solar cell turns light into electricity. Heat plays no part in making the power, which is why a crisp, bright January morning can be a good solar day. Cloud reduces output rather than stopping it, because the cells still respond to diffuse daylight scattered through the cloud.
Cold is, if anything, slightly helpful. PVGIS notes that module performance depends on temperature as well as light, and silicon cells convert light a little more efficiently when they are cool. For the London system in this guide, PVGIS estimates temperature and low-light effects together cost about 4.7% of output across the whole year. The winter problem is simply that there is far less light to work with: shorter days, a lower sun and more cloud.
How much does a UK system really generate month by month?
We modelled a typical domestic system in PVGIS 5.3: 4 kWp (kilowatt peak, the system's rated size), London, facing due south at a 35° pitch, with PVGIS's default 14% system losses and its SARAH3 satellite record from 2005 to 2023. These are long-run monthly averages, and any single month can be noticeably better or worse.
| Month | kWh in the month | kWh per day |
|---|---|---|
| January | 162 | 5.2 |
| February | 211 | 7.5 |
| March | 345 | 11.1 |
| April | 461 | 15.3 |
| May | 483 | 15.6 |
| June | 493 | 16.4 |
| July | 496 | 16.0 |
| August | 443 | 14.3 |
| September | 382 | 12.8 |
| October | 276 | 8.9 |
| November | 192 | 6.4 |
| December | 144 | 4.7 |
| Year | 4,089 | 11.2 |
At the Ofgem price cap unit rate of 26.32p per kWh that applies from 1 October 2026 (direct debit, GB average), December's 144 kWh is worth about £38 if you use all of it at home. June's output is worth more than three times as much.
How much of the year's output comes in winter?
| Period | kWh | Share of the year |
|---|---|---|
| December to February | 517 | 12.6% |
| November to February | 709 | 17.3% |
| October to March | 1,330 | 32.5% |
| May to July | 1,472 | 36.0% |
| April to September | 2,758 | 67.5% |
You will see higher winter shares quoted elsewhere, sometimes 15% to 25% for December to February. PVGIS does not support that for a south-facing London roof: the three darkest months give about an eighth of the year's electricity. The six months from April to September give about two thirds.
Does roof direction and pitch matter more in winter?
Yes, much more. In winter the sun sits low in the southern sky, so an east- or west-facing roof sees very little of it, and a steeper south-facing roof catches the low sun better.
| Roof | December | June | Year |
|---|---|---|---|
| South, 20° pitch | 112 kWh | 512 kWh | 3,919 kWh |
| South, 35° pitch | 144 kWh | 493 kWh | 4,089 kWh |
| South, 50° pitch | 166 kWh | 453 kWh | 4,054 kWh |
| East, 35° pitch | 60 kWh | 473 kWh | 3,280 kWh |
| West, 35° pitch | 61 kWh | 458 kWh | 3,166 kWh |
An east- or west-facing roof loses about a fifth of its annual output compared with south, but nearly 60% of its December output. That is fine if you judge the system annually. It matters more if you were hoping for winter help with a heat pump or an EV.
Does it matter where in the UK you live?
| Location | December | June | Year | December to February share |
|---|---|---|---|---|
| London | 144 kWh | 493 kWh | 4,089 kWh | 12.6% |
| Manchester | 113 kWh | 443 kWh | 3,544 kWh | 11.2% |
| Edinburgh | 89 kWh | 444 kWh | 3,614 kWh | 10.8% |
The further north you are, the shorter the winter day and the bigger the gap between seasons. Edinburgh's long summer days bring its annual total close to Manchester's in this model, but its December is about 38% below London's. The Energy Saving Trust's payback estimates reflect the same pattern: about 9 years in London and 11 to 12 years in Stirling.
What about snow, frost and short days?
- Snow: panels covered in snow produce very little until it melts or slides off. On an angled roof a light covering often clears once the sun gets to it. Never climb onto a roof or use a hose on frozen panels to clear them.
- Frost: a light frost on the glass usually clears as the day warms, and output returns with it.
- Dirt: the Energy Saving Trust says UK rain keeps panels clean if they are tilted at 15° or more. Flat or ground-mounted arrays may need an occasional clean.
- Shade: winter shade is longer. A tree or chimney that barely touches the panels in June can shade them for hours in December, which is why an MCS installer must assess shading before quoting.
How do you make winter solar count?
- Use power while it is being made. Winter output peaks around the middle of the day, so that is the time to run the washing machine or dishwasher if you are home.
- Do not size the system on winter output. A system big enough to cover December would export heavily for the rest of the year, usually at a lower rate than you pay to import.
- Think about tariffs, not just panels. The Energy Saving Trust's 2026 research found batteries earn more when charged on low-cost off-peak electricity for a heat pump than when they only store solar, which matters most in winter when there is little solar to store.
- Pair solar with the heating plan. If a heat pump is coming, the winter gap is exactly where the right tariff and, possibly, a battery make the difference. See solar with or without a battery.
When you compare quotes, ask for the monthly generation profile as well as the annual figure, so the December number does not come as a surprise. Smart Energie's solar, battery and EV page sets out what a survey covers, and the retrofit planner is a quick way to see where solar sits alongside insulation and heating in your home.
Common questions
Do solar panels work on a cloudy winter day?
Yes, at a reduced rate. Cloud scatters daylight rather than blocking it entirely, so the panels keep producing. On a heavily overcast December day expect a small fraction of the modelled 4.7 kWh daily average for a London 4 kWp system; on a clear, cold day it can do better than average.
Do solar panels work better in the cold?
Per unit of light, slightly. Silicon cells lose some efficiency as they heat up, so a cool panel converts light a little better than a hot one. The effect is small compared with the loss of daylight in winter, which is why winter totals are still far below summer.
Is solar worth it if I mainly use electricity in winter?
It can still be, because payback is earned across the year: the Energy Saving Trust estimates about 9 years in London with export payments. But solar will not cover winter use on its own. If your demand is mostly winter heating, look first at insulation and an efficient heating system, then add solar.
Should I get a battery to use solar in winter?
Not for winter solar alone. A 4 kWp system averages 4.7 kWh a day in December in London, and much of that is used as it is made, so a battery would rarely fill from the panels. In winter a battery earns its money by charging on low-cost off-peak electricity, which needs a time-of-use tariff.
Do panels need to be cleared of snow?
No. Leave it to melt or slide off. Climbing on a frosty roof is dangerous, and scraping or pouring hot water on the glass risks damaging the panels. A few days of lost winter output is worth very little money.