Do Solar Panels Work in Winter? What to Expect in the UK

Yes, solar panels work in winter. They generate from daylight, not heat, and they keep producing on cloudy days. But a UK winter means short days, a low sun and a lot of cloud, so output from November to February is much lower than in spring and summer. The cold itself isn’t the problem; panels actually work slightly more efficiently when they’re cool.

Here is what happens to a solar system over the winter, what you can do about it, and how to think about winter when you’re deciding whether solar is worth it.

Key points

• Panels generate from daylight, so they work in winter and on cloudy days, just much less.

• UK solar output is strongly seasonal. Government data on Feed-in Tariff solar systems shows the best quarter producing roughly three times as much as the worst, which is October to December.

• Cold weather doesn’t stop panels working. Short days, low sun and cloud are what reduce output.

• Snow usually slides off. Don’t climb on the roof or try to clear panels yourself.

• A battery charged from a cheap overnight tariff keeps working in winter even when solar can’t fill it.

• Judge a system on its whole year, not on December.

Why output drops in winter

Three things reduce winter output, and all of them are about light.

Shorter days. There are far fewer daylight hours in December than in June, so there’s less time to generate.

A lower sun. In winter the sun stays low in the sky. Its light passes through more atmosphere and hits the panels at a shallower angle, and low sun means longer shadows from chimneys, trees and neighbouring buildings. A roof that is clear of shade in summer can be partly shaded in winter.

More cloud. Panels still generate under cloud, because they use daylight rather than direct sun, but much less than in bright conditions. The Energy Saving Trust notes that cells don’t need direct sunlight and can work on cloudy days.

Put together, these effects are large. Government analysis of metered output from Feed-in Tariff solar installations shows the highest-output quarter of the year producing roughly three times as much as the lowest. The best quarter is spring and early summer; the worst is October to December.

Does cold weather affect solar panels?

Not in the way most people expect. Solar panels are slightly more efficient when they’re cool and slightly less efficient when they’re hot, which is why a bright, cold spring day can outperform a hot summer one. Manufacturers publish this as a temperature coefficient on each panel’s datasheet.

So a crisp, clear winter day is a good day for solar. It is the short daylight, not the temperature, that limits what you get.

What about snow and frost?

Snow. A covering of snow blocks light, so panels covered in snow produce little or nothing. Panels on a pitched roof are smooth and dark, and snow usually slides off as it begins to thaw. In London, heavy snow rarely lasts long.

Please don’t go up on the roof, use a ladder or try to clear panels with a brush or hose. It’s dangerous, and scraping can damage the glass and void the warranty. Wait for it to melt.

Frost. Frost on the glass clears quickly once the sun reaches it. It isn’t a concern.

What about batteries in winter?

A battery charged only from solar has little to store in midwinter. On many December days the panels will produce less than the house is already using, so nothing is left over to charge the battery.

Two things help:

• A cheap overnight tariff. Charging the battery in a cheap overnight window and using that electricity through the expensive part of the day works in January exactly as it does in June. Our guide to Octopus Flux and overnight charging explains how.

• Where the battery is. Most lithium batteries won’t charge below freezing, though they’ll keep discharging. A battery in a cold, unheated garage can look as though it has stopped charging on a frosty morning. Our guide to a battery not charging covers this.

Checking your system over the winter

Lower winter output is normal, but it’s still worth a quick look at your monitoring app now and then.

• Compare like with like. Compare this December with last December, not with June.

• Look for zero on a bright day. Very low output is expected on a dark, wet day. Nothing at all on a clear day is not.

• Watch for new shade. Low winter sun can expose shading from a tree or building that didn’t matter in summer.

If something looks wrong, our guides to solar panels not generating and solar generating less than it used to go through the common causes.

Is solar still worth it if winter is so poor?

For most London homes, yes, but judge it on the whole year. A well-designed system generates most of its output between spring and early autumn, and that is how an MCS generation estimate is calculated: as an annual figure for your roof, direction, pitch and shading. Our guide to the best direction and angle for solar panels explains how roof position affects that.

Winter is also a perfectly good time to install. The work is the same, and a system installed in winter is ready for the long days of spring.

Frequently asked questions

Do solar panels work on cloudy days?

Yes, but less. They use daylight, not direct sunshine, so they keep generating under cloud at a lower level.

How much do solar panels produce in winter?

Much less than in summer. It depends on your system size, roof and shading, so we don’t give a single figure. Government data shows the best quarter of the year producing roughly three times as much as the worst.

Do solar panels work at night?

No. They need daylight. At night the house uses grid electricity or a battery.

Should I clear snow off my panels?

No. Don’t climb on the roof or use tools on the panels. Snow usually slides off as it thaws.

Is it worth installing solar in winter?

Yes. Installation isn’t affected by the season, and the system will be ready for spring and summer.

Request a solar and battery quotation. We’ll model what your roof produces across the whole year and whether a battery would help you through the winter.