It is quite natural to wonder whether solar panel systems work in the winter. After all, it is general knowledge that solar panels reach peak production levels under a clear sky when more sunlight is received. Due to higher levels of yearly solar irradiation, southern countries such as Spain and Portugal can reach higher photovoltaic production levels than those of the UK.

However, does the relationship between production and clear weather make solar panels ineffective during winter, particularly in cloudy and or rainy regions of the UK? 

While solar panels generate less electricity during winter, they’re still able to contribute to the electricity production of your household when the days are short and or when the days are not clear. Solar panels generate less electricity in wintertime because there is less sunlight due to shorter days, not because of lower temperatures, as we’ll explain in detail further in this article.

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What impacts solar panel efficiency in winter? 

There are a few factors that result in a lower performance of a PV system in the colder months in comparison with the remainder of the year:

  • Shorter days lead to less sunlight received by solar panels; 
  • Overcastdays lead to a lower solar intensity; 
  • During snowy winters, thick layers of snow can cover the surface of solar panels, obstructing the passage of light that lowers PV production. 

However it should be noted that: 

  • Lower temperatures do not negatively impact PV production. While extremely hot temperatures have a negative effect on solar panels and that these work better under temperatures below 25º Celcius. A drop of 10º can lead to an efficiency leap of around 4%. 
  • Snowy weather, if moderate, can actually lead to higher PV production levels. Why? To begin with, because light is able to pass through thin layers of snow. Secondly, due to the albedo effect, the solar panels may receive sunlight from several directions, including from the ground.
  • Nowadays, solar panels can be equipped with optimisers, which help stabilise the amount of power generated, regardless of light and temperature fluctuations. 

Most of the factors previously mentioned are external and out of our control. However, there are some actions within our reach that may determine how much electricity solar panels can generate in winter, such as: 

  • Adjusting the tilt angle helps optimise the solar panels’ efficiency during the winter months. PV installations can have different tilt angles. There is, for example, the optimum all-year-round angle, which is always close to the latitude of the location in question, and there is the optimum winter angle, which is steeper, and can be calculated by adding 15º to optimum all-year-round angle. 
  • Executing basic maintenance measures on a periodic basis so that your solar panels can absorb as much sunlight as possible. Rain keeps solar panels clean, as it removes dirt and dust that would otherwise negatively impact photovoltaic production. Same with frost, unless the panels are damaged, and water can run through the cracks when the frost melts. Once a year it is helpful to clean the solar panels yourself with lukewarm water and non-abrasive brushes to ensure that their performance won’t be compromised. 

How much electricity do solar panels generate  in winter?

 As mentioned before, solar panels generate substantially less electricity at the height of the winter than at the peak of the summer. Let’s have a look at the solar panels output in winter vs summer in different parts of the UK, based on data found in PVGIS: 

  • In London, a 4.4 kWp system is expected to have a monthly output of 549.43 kWh in July. In January, that same system is expected to generate  around 164.96 kWh. 
  • In Manchester, a 6.5 kWp system is expected to generate around 756.42 kWh in May. In December, those levels should decrease to 184.02 kWh. 
  • In Norwich, a 2.2 kWp system is expected to  generate 82.5 kWh in January. The highest monthly output should be generated in May - 277.7 kWh. 

Whereas in London and Norwich the winter output is about a third of the summer output, in Manchester that gap is even larger, as the days are shorter in wintertime in Northern England than in other regions of the  country. This is countered with greater summer output due to longer summertime daylight hours.

 However, it should be noted that these calculations were made with a fixed-angle. As mentioned in the previous section, a steeper angle can make solar panels more effective during winter. 

Adding a battery to increase self-consumption

A battery is always a relevant component of a PV system, but comes particularly handy during the winter season, when photovoltaic production can be lower over a long period of time due to bad weather conditions. Why is that? Because solar batteries allow you to store the energy that is produced but not consumed immediately. In the winter season, when light is scarcer and days are shorter, this can be of great help, as batteries ensure that the light that the solar panels manage to absorb and convert into electricity is given some use in your household. 

On a financial level, they can also make the difference in the sense that they substantially increase the self-consumption levels - up to 90%. This means that, though the cost of a PV system with battery included will be higher, so will be the savings generated each month from the day of the installation onwards. 

Solar batteries should be kept in an insulated area, protected from the natural elements, in order to perform at their best and be a vital complement to your solar panels in winter. 

At Otovo, the members of our team are well aware of all this, and will provide you with useful information regarding factors that may impact the production of your solar panels. Our aim is to ensure the solar solution you install at your home suits your needs and goals and maximises your value for money. 

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