Does plug-in solar work in winter?

Adverts tend to quote a yearly figure and leave it there. This page shows what a plug-in kit actually makes month by month, in thirteen places from Brighton to Inverness, so you know what to expect before you buy one in October and wonder in December whether it is broken. It is not. It is winter.

How much does a kit make each month?

Here is a typical two-panel kit, about 930W of panels on an 800W inverter, facing south on a tilted frame in Birmingham. Birmingham sits in the middle of the range for sunshine, so it is a fair picture for much of England and Wales.

Month by month, for a 930W kit in Birmingham

South-facing on a tilted frame. July makes about three and a half times what December makes.

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Units (kWh) per month for 930W of panels in Birmingham, south-facing at 35 degrees, 14 per cent system losses. Source: PVGIS 5.3, European Commission Joint Research Centre, queried 26 September 2026; the monthly figures per kilowatt of panel multiplied by 0.93 and rounded by us. They are averages over the weather of 2005 to 2023, not a forecast for any one year.

December works out at about one unit a day. A summer day averages about three and a half. October to March, the darker half of the year, gives about a third of the year’s total in Birmingham, and December and January together make less than April does on its own.

How does winter output vary across the country?

This is where the map really matters. In summer, the north of Scotland is not far behind the south of England. In winter it falls a long way behind. The same 930W kit, in thirteen places:

Winter output of a 930W plug-in solar kit, south-facing at 35 degrees, in thirteen places in England, Scotland and Wales: December, January, the best month, November to February combined, and that period’s share of the year

Place	December	January	Best month	November to February	Share of the year
Brighton	36 kWh	40 kWh	July, 135 kWh	178 kWh	16.5%
Plymouth	34 kWh	38 kWh	May, 129 kWh	173 kWh	16.5%
London	34 kWh	38 kWh	July, 115 kWh	166 kWh	17.5%
Norwich	32 kWh	36 kWh	May, 116 kWh	160 kWh	16.7%
Birmingham	31 kWh	35 kWh	July, 110 kWh	153 kWh	17.0%
Cardiff	30 kWh	34 kWh	May, 123 kWh	154 kWh	15.9%
Leeds	30 kWh	32 kWh	May, 110 kWh	146 kWh	16.5%
Manchester	26 kWh	25 kWh	May, 105 kWh	128 kWh	15.5%
Newcastle	25 kWh	32 kWh	May, 113 kWh	142 kWh	16.1%
Edinburgh	21 kWh	27 kWh	May, 111 kWh	125 kWh	14.9%
Aberdeen	19 kWh	25 kWh	May, 113 kWh	114 kWh	13.8%
Glasgow	18 kWh	22 kWh	May, 108 kWh	109 kWh	13.7%
Inverness	13 kWh	17 kWh	May, 105 kWh	90 kWh	12.0%

PVGIS 5.3, European Commission Joint Research Centre, queried 26 September 2026 at the centre of each place: one kilowatt of panel, south-facing at 35 degrees, 14 per cent system losses, radiation database PVGIS-SARAH3 covering 2005 to 2023. Converted to a 930W kit and rounded by us. Shares are worked from the unrounded figures.

Over a whole year, Brighton makes about 43 per cent more than Inverness. In June the gap is only about a third. In December, Brighton makes nearly three times as much. If you live in Scotland, a plug-in kit is very much a spring and summer machine, and its winter contribution is small.

Notice too that the best month is often May rather than midsummer. That is the long-term average weather showing through: across these thirteen places, May is the best month in ten of them.

Why does output fall so far in winter?

Mostly because there is so much less daylight, and the sun that does appear is low in the sky, so its light is weaker by the time it reaches the panel. Cloud plays its part as well. The PVGIS figures above already include the clouds: they are averages over nineteen years of real weather, not clear-sky ideals, so a grey December is built into them.

What the figures cannot include is your own surroundings. PVGIS allows for hills and high ground on the horizon, but it does not know about the house opposite, your hedge or the tree at the end of the garden. A low winter sun casts long shadows, so a spot that is in full sun in June can sit in shade for much of a December day. Before you choose where a kit goes, look at the spot on a bright winter morning as well as a summer one.

Is a kit worth anything in winter?

A little. Here is the most it could be worth, in Birmingham, if every single unit the kit made were used in the house at the current price cap of 26.32p a unit:

• December: about 31 units, worth at most about £8.
• November to February together: about 153 units, worth at most about £40.
• The whole year, for a home where someone is sometimes in during the day: about £95, the figure our calculator gives for Birmingham.

Those winter numbers are ceilings, not predictions. In practice some of what a kit makes always goes unused while nobody needs it, and anything unused flows out to the grid and, for almost everyone, earns nothing. That said, in midwinter a kit’s output is small next to what most homes draw through the day, so less of it is likely to go to waste than in summer. We have not measured how much less, so we do not put a figure on it.

The honest summary: buy a plug-in kit for what it does across the year, not for what it does to a January bill. About three quarters or more of the output, from 76 per cent in London to 82 per cent in Inverness, comes between March and September. The is it worth it? guide works through four different households.

Should I wait until spring to buy?

There is no rule that says you must, and no reason you have to. A kit bought in October will make its smallest amounts first, which can feel disappointing, but over the years it owns the payback is the same whichever month you start. Buying in autumn does mean the first few months will not tell you much about whether the kit is working well.

Two things are worth doing in winter whenever you buy. First, check the exact model reference on the official register before you pay; our kit tracker links each kit straight to its entry. Second, if the kit needs a new or outdoor socket, book the electrician before the kit arrives. Prices, though, are a separate question: see what a kit costs.

Does plug-in solar work in a power cut?

No. Winter storms are when people most often ask this, so it is worth being clear. A plug-in kit is designed to work alongside the grid, not instead of it. The simple notify-only route that plug-in kits use under the electricity safety regulations is for small sources that disconnect when the network supply is lost. So when the power goes off in your street, the kit stops feeding your home too.

A battery would change that in principle, but a battery is outside the current rules: no compliant kit on the register includes one. See batteries and plug-in solar.

Electricity Safety, Quality and Continuity Regulations 2002, regulation 22, on legislation.gov.uk, read 26 September 2026: regulation 22(2) covers small sources that disconnect when the network supply is lost. Batteries: SI 2026 No. 848 and the Plug-in Solar Device Interim Product Specification version 2, read 26 September 2026.

How can I get the most out of a kit in winter?

• Use the middle of the day. Winter output comes in a short window around noon. A washing machine or dishwasher on a delay timer set for late morning uses more of it than one run in the evening.
• Batch on the bright days. A bright winter day makes far more than a dull one. That is the day for the laundry.
• Watch for new shade. Check whether the low sun puts the panels behind a fence, a wall or a neighbour’s roof for part of the day, and move a free-standing frame if you can.
• Keep the panels clear, safely. If leaves or snow cover a panel within easy reach from the ground, clear them gently. Never climb onto anything to reach a panel.
• Look at the app. Most microinverters report to one. A low December figure next to the table above is normal. A figure of zero on a bright day is worth investigating.

For what a kit can and cannot power at any time of year, see what will plug-in solar run?

Questions people ask

Do plug-in solar panels work on cloudy days?

Yes, they still generate, just less than in sun. The monthly figures on this page come from PVGIS 5.3 and are averages over the real weather of 2005 to 2023, so cloudy days are already counted in them.

How much does a plug-in solar kit make in December?

For a 930W kit facing south on a tilted frame, from about 13 units in Inverness to about 36 in Brighton, and about 31 in Birmingham. That is roughly one unit a day in the Midlands. Figures from PVGIS 5.3, queried 26 September 2026.

What share of a year’s solar comes in winter?

November to February together give between 12 per cent of the year’s output in Inverness and 17.5 per cent in London, across the thirteen places we hold data for. March to September gives from 76 to 82 per cent.

Will plug-in solar keep my lights on in a power cut?

No. A plug-in kit has to disconnect when the grid supply is lost, so it stops working in a power cut. It has no battery to fall back on, because batteries are outside the current rules.