Do Solar Panels Work in Winter? What a South Coast System Really Generates from October to February
Do Solar Panels Work in Winter? What a South Coast System Really Generates from October to February
Last updated: 23 September 2026 | 11 min read | By No1 Solar Care
On 26 August Ofgem confirmed the energy price cap rises 4% from 1 October, to £1,723 a year for a typical dual-fuel household. Electricity on a default tariff will average 26.32p per kWh, with a daily standing charge of 54.83p. For the first time, that unit rate carries no VAT: the government has removed it from electricity bills from 1 October 2026 to 31 March 2027.
Eight days later, on a Wednesday in September, the sun set at Hurn at 7.20pm. By 21 December it will set at 4.04pm.
Those two facts arrive together every autumn and they produce the same question in every solar-owning household on the South Coast: is this thing actually doing anything between now and March, and does it matter that the electricity it's replacing just got more expensive? Short answers: yes, less than you'd like, and yes it matters more than it did in July.
In summary: Solar panels work in winter, but Met Office data for Bournemouth shows December delivers roughly a quarter of July's sunshine hours. A 4 kW South Coast system that generates around 3,400 kWh a year produces about 550 kWh across November to February. At the October 2026 price cap rate of 26.32p/kWh, that winter output is still worth around £110.
Do solar panels work in winter?
Yes. Solar panels generate from light, not heat, and they produce electricity on every day of the year that has daylight. Output falls in winter because days are shorter, the sun is lower and cloud cover is heavier, not because the panels stop working. Cold weather actually improves panel efficiency slightly.
That last point genuinely surprises people. Silicon panels lose output as they heat up, typically 0.3–0.4% per degree above 25°C on the manufacturer's datasheet. A panel on a Poole roof at 2°C on a bright January morning is converting more of the light it receives than the same panel at 55°C in a July heatwave. The problem in January is that there's a fraction of the light to convert.
The Energy Saving Trust puts it plainly: cells don't need direct sunlight and work on cloudy days. A dull, bright-grey overcast day in February might give you 15–25% of a clear-sky day. A dark, rain-lashed one might give you 5%. Neither is zero. What you will not get is anything at all before the sun is up, and in December on the South Coast that's a 16-hour gap.
How much less do solar panels generate in winter on the South Coast?
Roughly 70–75% less per month at the bottom of the year than at the top. The Met Office's 1991–2020 average for Hurn, just outside Bournemouth, records 61.08 hours of sunshine in December against 234.33 in July. November to February together hold about 16% of the year's sunshine; May to August hold 50%.
Here's the full year for a typical 4 kW system, using the Met Office sunshine hours as a proxy for the share of annual generation. We've assumed 850 kWh per kW installed per year, the figure we use for South Coast systems, which gives 3,400 kWh annually.
Source: Met Office location-specific long-term averages, Hurn, 1991–2020. Generation estimates are ours and use sunshine hours as a proxy; actual output also depends on irradiance intensity, roof pitch and orientation, and shading.
Two things stand out. December at 117 kWh is a bit under 4 kWh a day, which on a home using 7–10 kWh will cover the fridge, the router, the lights and not a great deal else. And the drop is not a cliff. October still delivers nearly twice December, and by March you're back above 240 kWh. The properly thin period is about twelve weeks long.
What is winter solar output worth at the October 2026 price cap?
Around £110 for the four months from November to February on a 4 kW system, using Ofgem's new default electricity rate of 26.32p/kWh, 55% self-consumption and a 12p Smart Export Guarantee rate. Across the full year the same system is worth roughly £680–£720 depending on your export tariff.
The maths for the winter period: 556 kWh generated, 306 kWh used directly at 26.32p (£80.50), 250 kWh exported at 12p (£30). The self-use figure is the one that moves with the price cap, and it just moved. Ofgem's October–December 2026 unit rates replace a Q2 2026 figure of 24.67p that we were using in our savings calculator, so every kWh your panels keep you from buying is worth about 7% more than it was in the spring.
Standing charges are the part solar can't touch. At 54.83p a day that's £200 a year before a single unit is used, and the panels don't change it.
One more number worth having. If you can get onto a 15p fixed SEG rate, which several major suppliers were offering in September 2026, the winter export figure goes from £30 to £37.50. Not transformative, but free, and worth a ten-minute switch.
Why does winter expose faults that summer hides?
Because there's no headroom. A system that's 20% down in July still produces 360 kWh and nobody notices. The same 20% in December takes 117 kWh to 94, and takes a system that was just about covering the daytime base load to one that isn't. Low light also raises the bar an inverter has to clear before it starts at all.
That second point matters more than it sounds. Inverters need a minimum DC voltage from the panels before they wake up in the morning. On a healthy string that arrives early. On a string with a degraded panel, a high-resistance connector or a shaded corner, the voltage creeps up more slowly and the inverter sits idle for an extra half hour at each end of an already short day. In June that's a rounding error. In December it can be a fifth of the available light.
The same goes for soiling. The sun in December sits about 16° above the horizon at midday in Bournemouth, against 63° in June. At that angle, moss and grime along the lower edge of the panel, which the summer sun sails over, casts a shadow across the bottom row of cells for most of the day. On the South Coast the salt film that builds up over a stormy autumn adds to it.
The key takeaway: winter is when a marginal system becomes a broken one, and it's also the season when most people stop looking at the app. If your December figure is below about 100 kWh on a 4 kW system with clear-ish weather, something other than the season is wrong.
Should I get my solar panels cleaned or checked before winter?
Checked, yes. Cleaned, only if the check says so. Autumn on the South Coast is the right moment for an inspection because it comes after the storm season has started loosening things and before the low-light months make every loss expensive. A reflex clean without knowing whether soiling is the actual problem is money spent on a guess.
What an autumn check is looking for is specific. Loosened fixings after the first named storms of the season. Debris and leaf litter behind the array where it traps water against the tiles. Moss establishing along lower edges now the surfaces stay damp. Nesting material from the summer under the panels, which the gulls will be back to add to in spring. Inverter fault logs that have quietly accumulated through the summer while the generation figure looked fine.
The Energy Saving Trust notes that UK rain will keep panels clean if they're tilted at 15° or more, which is true for loose dust. It does nothing for the bonded stuff. A full solar panel service covers both: we call ours the 21-point Solar MOT, £195, written report the same day. If cleaning turns out to be needed, the cleaning is quoted separately and the £195 comes off.
Is a solar battery worth it in winter?
Not for storing solar, no. On a 4 kW system there's almost no winter surplus to store; most December days you'll use everything the panels make as it's made. Where a battery earns its keep in winter is on a time-of-use tariff, charging from cheap overnight grid electricity and discharging through the expensive evening peak.
That's a different business case from the one most people bought the battery for, and it's worth being honest about. A battery bought to "store summer sun for winter" doesn't do that; nothing domestic does. A battery paired with an off-peak tariff can still cut a winter bill meaningfully, because you're buying the evening's electricity at the overnight rate instead of the default 26.32p.
If you already have a battery, winter is the season to check it's actually doing this. We regularly find batteries on a summer-optimised setting that sit at 10% charge all evening in January because the solar never filled them and nothing told them to fill from the grid. A battery health check is part of the MOT on any system that has one.
Is winter a good time to install solar panels?
For the next six months, yes, for a reason that has nothing to do with the weather. The 0% VAT rate on domestic solar installation ends on 31 March 2027. A system fitted in January is installed at 0% and is up and running for the spring ramp, when the Bournemouth table above shows generation doubling between February and April.
The weather itself is a smaller factor than people assume. Installation is a one-day job for most homes. Scaffolders and MCS engineers are easier to book in November than in May. The system commissions on a grey day exactly as it would on a sunny one; it just doesn't show you a big number until March.
What winter does give you is a cleaner decision. Sizing a system in July, with the app showing 25 kWh days, tempts people into a bigger array than they'll ever use. Sizing it with the winter figures in front of you produces a more honest design, usually with a battery and a tariff plan built in from day one rather than bolted on later. Our installation team is MCS certified and, because we maintain what we fit, the engineer who does the January install is the same one who comes back for the first annual check.
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Frequently asked questions
How much electricity do solar panels generate in December in the UK?
On the South Coast, a 4 kW system generates roughly 115–130 kWh in December, or about 4 kWh a day, based on Met Office sunshine averages for Bournemouth. That's around a quarter of a typical July. Further north the December figure is lower; Cardiff's December sunshine is about 17% below Bournemouth's.
Do solar panels work on cloudy days?
Yes, at reduced output. Panels respond to light intensity, and a bright overcast sky still delivers a useful fraction of clear-sky irradiance, typically 15–25%. A dark, heavily overcast day might give 5–10%. They don't need direct sun, but they do need daylight, so nothing is produced before sunrise or after sunset.
Do solar panels work better in cold weather?
Slightly, yes. Panel efficiency falls as cell temperature rises, typically by 0.3–0.4% per degree above 25°C. Cold, bright winter days therefore convert light more efficiently than hot summer ones. The gain is real but small, and it's swamped by the far larger effect of shorter days and lower sun.
Does snow stop solar panels working?
While it covers them, yes. Snow is rare on the South Coast and usually slides off a pitched array within a day as the dark glass warms. Don't clear it yourself; the risk of falling or cracking a panel outweighs a day's December generation, which is only about 4 kWh anyway.
What does the October 2026 price cap mean if I have solar panels?
Every unit your panels generate and you use directly is now worth 26.32p rather than the previous default rate, so your self-consumption savings rise by roughly 7%. Export payments under the Smart Export Guarantee are set by your supplier, not the cap, so they don't change unless you switch tariff. Standing charges are unaffected by solar.
Should I turn my solar panels off in winter?
No. There is no benefit to switching a system off and several downsides: you lose the generation, you lose the monitoring data that tells you whether anything's wrong, and some inverters and batteries behave badly after long periods without power. Leave it running and keep an eye on the monthly figure.
Why is my solar generation so low in winter?
Mostly because of the season: December on the South Coast has about 26% of July's sunshine. If your December output is below roughly 100 kWh on a 4 kW system, or has dropped more than a few per cent against last December, that's a fault rather than the weather. Common causes are a degraded string, a high-resistance DC connector or lower-edge soiling shading the bottom row of cells.
The winter drop is real and it's roughly three-quarters. It is also the one part of owning solar that's completely predictable, because the Met Office has been measuring it at Hurn for thirty years. What isn't predictable is whether your system is producing its 117 kWh in December or somebody else's 80, and the only way to know is to look.
The price cap just made the difference worth about 26p a unit. Worth looking.