With the clocks set to go back, the days will inevitably seem shorter as the average daylight hours drop from the heady 14-16, we experience in the summer months, to only around 8-10 in the autumn and winter months.
A lot is made of how shorter days and less sunshine affects the mental and physical well-being of people, but less is known about what impact fewer sunshine hours has on the green energy ambitions of the UK homeowner.
In this article we will discuss the solar panel output in winter vs summer in the UK, how well solar panels work in cloudy weather and how much difference in performance there is throughout the shorter winter days.
Solar Panel Output Winter Vs Summer UK
Producing energy from solar panels is a complicated process, but in very simple terms, they produce energy from sunlight when the electrons in the photovoltaic [PV] cells that make up a panel, have electrons displaced by the photons in sunlight to create the flow of electricity.
Before we compare the performance of panels in winter and summer, we should first look at the typical energy output from solar panels and how this might meet the needs of the average homeowner in the UK.
Firstly, energy usage is calculated in kilowatt hours (kWh) and one kWh is defined as enough power to light a 100-watt lightbulb for 10 hours. As a comparison, the average tumble dryer will use around 4.5 kWh of energy for a single cycle and OFGEM (Office of Gas and Electricity Markets) estimates the typical household uses 2,700 kWh of electricity in a year.
The typical solar panels fitted in the UK will be rated 350W and on average will produce around 265 kilowatt hours (kWh) of electricity per year in the UK. So, it’s easy to see that for the average homeowner, investing in a 10-panel solar array will meet their annual household electricity usage.
If they specify better performing, higher rated but more expensive panels with a rating above 500W, increase the number of panels, or ideally do both, then the average homeowner can easily produce an excess of electricity throughout the year – this is where a solar battery storage system is essential.
How much energy do solar panels generate in Winter in the UK?
According to the Energy Saving Trust, in the winter months, solar panels will generate around a 5th of the energy production typically seen through the summer and spring, but it is worth comparing the output on the longest and shortest days to see the difference in output.
This year, Wednesday 21 June was the UK’s longest day, with almost 16.5 hours of daylight, which would generate around 6 kWh from a single 350W solar panel. On the shortest day, which this year will be Friday 22 December, the 7 hours of daylight would produce only 2.5kWh.
However, these would be ideal figures in a perfect world, with near 100% panel efficiency, whilst ignoring the strength of the sunlight, panel orientation (North, South etc.) and the angle at which it strikes the solar panels, all of which affects the real-world output.
It is a good indicator though, that whilst output varies from day to day, it will peak in the summer and drop throughout the year to a low near Christmas. But rain, snow and low temperatures can also affect the output from panels, but perhaps not as you might think.
Occasional heavy rainfall during the winter can be favourable for solar energy production. Solar panels often work better in sunshine, immediately after heavy rain as they will have been washed clean of any dust or dirt that might block light reaching the cells within the panel.
The same is also true with snow in the UK. The typical installation angle for solar panels matches that of rooves in UK, 30 to 45 degrees from the horizontal, which allows snow to slip easily of the smooth glass surface, once the temperature warms a little. Again the panels are cleaned by this action and their efficiency will again be improved for when the sun shines.
Do solar panels work in cloudy weather?
The UK has a temperate climate, which means we typically experience cool, wet winters and warm, wet summers. Our climate rarely features the extremes of heat or cold, drought or wind that are common in some other climates.
Importantly, bright sunlight is not necessary for panels to produce electricity, only some daylight is required to harness the sun’s renewable energy, although the process will be less efficient in overcast cloudy conditions.
Certain types of cloud cover can even increase the level of sunlight the panels can convert into energy. Higher cloud formations can create a phenomenon known as ‘cloud-lensing’, due to the water and ice particles they contain, when solar irradiance is higher just as a cloud passes over a solar array, than it would be in full sunlight.
This happens when water and ice molecules reflect and refract the sunlight, acting like tiny magnifying lenses to boost the amount of light hitting the panel. When the solar panels are shaded by the clouds, they are cooler and more efficient, so as the sun appears from behind a cloud, it can deliver a 5-10 minute boost of energy before the panels sit once again in direct sunlight.
Do solar panels work well in cold weather?
You might also think that colder temperatures will lower the efficiency of solar PV systems. However, colder conditions help solar panels function more efficiently and will produce more power for each hour of sunshine during short sunny days of winter as opposed to warm summers.
Surprisingly, the output is higher in colder conditions because the electrons we need to move with photons of light, are at rest in cooler temperatures. When these electrons are activated by increasing sunlight a greater difference in voltage is achieved, creating more energy from the panel.
Should I include a solar battery system with my solar PV system?
A solar battery storage system is essential to unlock the true potential of a solar panel installation to deliver electricity when you need it to cut your energy bills. In the summer, the chances are you will not use all the power your solar panels generate on long sunny days, when demand in your home is lower, with lights on for shorter periods and lower heating needs.
However, when you are home in the evening and electricity usage is potential at its maximum, with lights, TV, computers, cookers, washing machines etc., running, a battery storage system will allow you to store the day’s output and use it when the sun has set.
In the winter, when there may not be enough sunshine to fill the batteries, a solar battery storage system can be charged overnight with cheap off-peak tariffs for use during the day if there isn’t sufficient sunshine next day either.
A solar battery system added to your existing panels or purchased as a part of an integrated system makes perfect sense with energy prices unlikely to fall to previous levels. If you still need persuading of the benefits of solar panels, a solar batter storage system or any part of the equation, then please get in touch and we’ll talk you through the next steps. If you decide to install solar panels, inverters and an integrated solar battery storage system, you will see from our Trustpilot reviews that Sunergy Renewable is one of the leading system designers and installers, ready to help you cut your energy bills, so please get in touch.