How to get more from your solar panels in winter

Key takeaways

• Solar panels still generate electricity throughout winter. Output falls because the days are shorter, the sun sits lower, and clouds reduce the available daylight – not because it’s cold.
• Keeping panels free from persistent shade and debris, while monitoring for unexpected performance drops, helps protect the electricity they can generate.
• Using more electricity during daylight, storing spare solar in a home battery and choosing the right tariff can help you get more value from every winter kilowatt-hour.

Winter isn’t exactly famous for sunshine in the UK. The days are shorter, the clouds hang around, and it can feel as though the sun has taken a few months off.

But your solar panels don’t. 

Solar panels continue generating electricity throughout winter, even on cold and cloudy days. They’ll produce less than during summer, sure, but there are ways to protect their output and make better use of every bit of electricity they generate.

Some involve your panels. Others involve when you use energy, where you store it and how much you pay for anything you still need from the grid.

Let’s start by separating those things, because getting more electricity from your panels and getting more value from that electricity aren’t quite the same.

Solar panels still generate electricity in winter

Solar panels use daylight to generate electricity. They don’t need blazing sunshine or warm weather, which means they’ll keep working on cold and overcast winter days, too. In fact, solar cells can convert daylight into electricity more efficiently in cooler temperatures. 

So it’s not the cold that’s the problem. The real troublemakers are shorter days, a lower sun and more cloud cover, which leave your panels with less light to work with. As a result, winter generation may be around 10–25% of what you would expect during summer.

That doesn’t mean something is wrong with your system. December and January are naturally the quietest months for solar generation, while spring and summer do most of the heavy lifting.

A good solar system is designed around what it can generate across the whole year, not what it produces during one particularly gloomy Tuesday in December.

Why solar panel output falls during winter

We’ve touched on a couple already, but there are several things that come together to reduce solar generation during the colder months.

1. There are fewer daylight hours

This is the big one. The sun rises later and sets earlier, giving your panels a much shorter window in which to generate electricity.

Take London as an example. Around the longest day of the year, the sun rises at approximately 4:43am and doesn’t set until 9:21pm. Around the shortest day, sunrise is closer to 8:04am and sunset arrives before 4pm.

That’s almost nine fewer hours of daylight. So, while your panels can generate from early morning until well into the evening during summer, most winter generation has to be squeezed into the middle of the day.

2. The sun sits lower in the sky

You know that low winter sun that somehow finds the one gap in the curtains and shines straight into your eyes? It reaches your solar panels from that lower angle too.

During summer, the sun climbs much higher and its light hits your roof more directly. In winter, it follows a lower path across the sky, so less direct light may reach the surface of your panels.

It also creates much longer shadows. A tree, chimney or neighbouring building that barely shades your panels in June could cover a much larger part of your solar array in December, reducing how much electricity it can generate.

3. Winter often brings more cloud cover

It wouldn’t be a British winter without a few grey skies. Longer periods of thick cloud, rain and unsettled weather are common during the colder months, leaving your panels with less daylight to turn into electricity.

Clouds don’t block every ray. Some daylight still passes through or bounces between the clouds before reaching your roof, which is why solar panels continue generating on overcast days. But that light is weaker than the direct sunshine they receive beneath a clear sky, so output is usually lower.

And because winter days are already shorter and the sun sits lower, heavy cloud takes another bite out of the limited daylight available. That’s why a clear, crisp December morning can be surprisingly productive, while a dark and rainy afternoon may produce very little.

4. Autumn and winter debris can get in the way

This isn’t a problem for every home, and it isn’t one of the main reasons solar output falls in winter. But autumn leaves and debris carried by wet or windy weather can sometimes settle on or around your panels, particularly when they sit close to trees.

Anything that remains in place can stop daylight reaching part of the panel and reduce how much electricity it generates. Bird mess and everyday dirt can do the same, although they’re hardly winter-exclusive problems.

Then there’s snow. It’s not a regular concern for most UK homes, but a thick covering can temporarily stop generation because no daylight can reach the solar cells beneath it.

Thankfully, roof-mounted panels are usually installed at an angle. Rain takes care of plenty of everyday dirt, while leaves and snow will often slide away naturally. So a little grime, or the rare snowy morning, isn’t a reason to go scrambling up a ladder.

How much electricity do solar panels generate in winter?

There isn’t one figure that applies to every UK home. But an example helps bring the seasonal difference to life.

Imagine a south-facing 4kWp solar system in central England with roughly ten modern 400W panels. In a fairly typical year, it might generate around 3,800kWh of electricity.

Approximately 69% of that could arrive between April and September, giving the home around 2,620kWh. The remaining 31% (roughly 1,180kWh) would be generated between October and March.

And even that winter electricity won’t arrive evenly. In this example, the system might produce around 330kWh in March but only 115kWh during December.

That’s only an illustration, not a forecast for every roof across the UK. Your actual winter solar output will depend on:

• The number and output of your panels
• Your roof’s direction and angle
• Where you live
• Nearby trees, buildings and chimneys
• The weather
• The condition of the panels
• The design of the complete system

Some winters are greyer than others, too. So even the same solar system can generate different amounts from one year to the next.

That’s why comparing one particularly gloomy week with your annual estimate won’t tell you very much. Solar generation naturally rises and falls throughout the year, so it’s more useful to compare your output with what your system would normally generate at the same time of year.

Your solar monitoring can help. If generation suddenly falls well below what you’d expect in similar weather, it may be worth checking for new shade, debris or a problem with the system.

How to maximise solar panel output in winter

You can’t make the winter days longer. Sorry about that. But you can help make sure your panels get as much of the available daylight as possible.

1. Keep an eye on winter shade

Because the sun sits lower during winter, shadows stretch much further across your roof.

Have a look at your panels at different points during the day, particularly around the middle of the day when winter generation is usually strongest. You may find that nearby trees or overgrown branches are casting shade that wasn’t there during summer.

Cutting back vegetation may help, provided the trees belong to you and aren’t protected. If the work involves height, large branches or anything near power lines, leave it to a professional.

2. Deal with persistent leaves and debris safely

Rain handles much of the routine cleaning for roof-mounted solar panels. But if leaves or dirt remain in place and noticeably affect generation, the panels may need attention.

Follow the manufacturer’s care instructions and use a professional solar-panel cleaner for anything that can’t be reached safely from the ground. Don’t climb onto a wet or icy roof, and don’t use abrasive brushes or pressure washers that could damage the panels.

Professional cleaning also needs to make financial sense. Paying hundreds of pounds to recover a tiny amount of lost winter electricity may leave you worse off, not better.

3. Leave roof-level snow alone

A thick covering of snow can temporarily stop your panels generating, but clearing it yourself usually isn’t worth the risk.

Don’t climb onto an icy roof or pour hot water onto frozen panels. The sudden temperature change could damage the glass just like a car window. Plus, you could do considerably more damage to yourself.

Snow often begins sliding from tilted panels as soon as conditions improve. For most UK homes, waiting for it to clear naturally is the safer answer.

4. Watch for unusual drops in performance

Lower winter generation is normal. A sudden or unexplained drop might not be.

Your monitoring should help you compare performance over time. If one panel (or string) is producing far less than the others, or the complete system stops generating on a bright day, contact your installer rather than trying to diagnose electrical equipment yourself.

Sometimes the most useful thing you can do is notice that something doesn’t look right.

5. Get the design right from the beginning

If you’re still considering solar panels, the original system design will have a much bigger effect than any winter housekeeping.

A good installer will assess:

• The direction and angle of your roof
• Shading at different times of year
• The usable roof space
• The output and placement of each panel
• How the panels connect to the inverter
• Your annual electricity use
• Whether battery storage suits your home

South-facing panels tend to generate the most electricity across the year, but east- and west-facing panels can still perform well and spread generation more evenly between the morning and afternoon.

Panel angle can also affect how the system responds to the low winter sun. That’s something to consider while designing the system – but not a reason to start adjusting roof-mounted panels twice a year.

Use more electricity while your panels are generating

Protecting solar output is only half the story. The other half is making good use of the electricity once you’ve generated it.

Without a battery, any solar electricity your home doesn’t use at that moment will normally be exported to the grid. You can be paid for it, but using your own electricity may sometimes be worth more than selling it and buying electricity back later.

Think of winter solar as a smaller window of home-grown electricity. The trick is moving more of your energy use into that window.

Washing machines and dishwashers are good places to start because many have delay timers. On brighter days, you could also charge an electric car or prepare food while your panels are generating.

You don’t need to turn everything on at exactly midday. If your appliances demand more electricity than the panels are producing, the rest will simply come from the grid. But spreading high-energy jobs across the daylight window can help you use more solar directly.

And, as always, don’t run washing machines, tumble dryers or dishwashers when you’re out or asleep unless the manufacturer says it’s safe to do so.

A home battery can save winter solar for later

A home battery doesn’t make your solar panels generate more electricity. It helps you keep more of what they produce.

If your panels generate more than the home needs during the day, the spare electricity can charge the battery. You can then use this stored electricity during the evening, when the sun has gone down and household demand is often higher.

Winter changes the job slightly. On dark days, your panels may not produce enough electricity to fill the battery. But that doesn’t make the battery useless.

With a compatible time-of-use tariff, it may also charge from the grid when electricity is cheaper. You can then use that stored energy later when grid prices rise.

So, during summer, the battery may spend more time storing abundant solar electricity. During winter, it can help you make better use of both home-grown solar and cheaper electricity from the grid.

The right electricity tariff can lower winter energy costs

Some electricity tariffs charge the same amount throughout the day. Others offer lower prices at particular times or change in response to the energy market.

During winter, when your home is likely to import more electricity, those price differences can matter.

A home battery could charge from the grid during a cheaper period, then power the home when electricity becomes more expensive. If the day turns out brighter than expected, your solar panels can contribute too.

The difficult part is deciding when to charge, store, use or sell electricity. Weather forecasts change. Electricity prices move. Your home’s energy use doesn’t follow a perfect timetable either.

You could try to manage all of that yourself. But you probably have better plans for your winter evenings.

That’s where intelligent home energy controls come in, like Aira Intelligence. 

Solar panels can help power a heat pump in winter

A heat pump runs on electricity, so it can use electricity generated by your solar panels whenever it’s available.

There is a seasonal mismatch to consider, though. Your home usually needs the most heating during winter, which is exactly when solar panels produce the least electricity.

Solar can still cover part of the heat pump’s demand during brighter periods. A battery can save some of that electricity for later, while the grid fills any remaining gap.

The goal isn’t necessarily to run the heat pump entirely from your roof every hour of winter. For most UK homes, that would require an enormous solar array and a very large battery.

The more realistic goal is to use solar whenever it makes sense, buy electricity when it’s cheaper and keep your home cosy without constantly thinking about where the next kilowatt-hour is coming from.

Read our guide to powering a heat pump with solar panels for a closer look at how the two technologies work together.

Aira brings solar, battery and heat pumps together

Winter gives your home energy system a harder job. There’s less solar electricity available just as your home starts using more energy for heating, lighting and long evenings indoors.

That’s why connecting everything matters.

With Aira, your solar panels, Aira Power Store (home battery), Aira Heat Pump and electricity tariff can work as one joined-up system. Powered by Aira Intelligence, your system looks at your energy needs, solar generation, battery level, electricity prices and the weather ahead.

It can then decide when it makes more sense to use electricity, store it, buy it for less or sell it back to the grid. In other words, your solar panels make the electricity, and Aira Intelligence helps make more of it.

No weather-watching. No constant battery management. Just cleaner energy working quietly around your home. Saving you even more on your energy bills, every day.