PV systems in winter

Does a photovoltaic system only work in summer?

No, PV systems work in winter too!

It is a cliché that many people believe a PV system produces nothing in winter! This misconception largely stems from people equating PV systems with solar thermal systems. The latter are also mounted on roofs, but serve purely to generate hot water. Hence, many draw the conclusion that PV systems only work when it is warm and the sun is shining, meaning in summer.
With this article, we want to shed some light on the subject and show you that PV systems can also be used productively in winter.

So, how do PV systems actually work?

We have already explained the technical requirements for a photovoltaic system in an earlier article so you know what is needed on site to produce electricity.
How does it happen, though, and which environmental circumstances and influences must be present for a PV system to productively fulfill its task?

Is GLOBAL RADIATION one of the factors deciding PV yield?

Global radiation is the total amount of shortwave solar radiation hitting a horizontal surface such as the earth's surface. It consists of direct radiation and diffuse radiation.
Direct radiation is solar radiation that reaches the earth's surface without being scattered by the atmosphere. It is strongest when the sun is high in the sky, meaning during summer months and at midday.
Diffuse radiation is solar radiation scattered by clouds, water vapor, and other particles in the atmosphere. It is strongest when the sun is low in the sky, meaning during winter months, in the morning, and in the evening.
Then there is the radiation angle, which also depends on the season and time of day.
Global radiation is therefore an important factor for the earth's climate. It is the main source of energy for warming the earth's surface and atmosphere.

Which factors influence global radiation?

There are several additional factors that come into play and influence global radiation. We would like to highlight the following:

• Geographical latitude: Global radiation decreases with increasing latitude. This is because the sun is higher in the sky at the equator, allowing more direct radiation to reach the surface.
• Season: Global radiation increases in summer and decreases in winter. This is because the sun shines longer during the day in summer, and the days are longer.
• Time of day: Global radiation increases at midday and decreases in the morning and evening. This is because the sun is higher in the sky at midday and delivers more direct radiation.
• Weather conditions: Global radiation decreases under cloudy skies. This is because clouds absorb or reflect part of the solar radiation.
• Air pollution: Air pollution can increase global radiation by increasing the scattering of solar radiation.

Looking at this from another perspective, you can see that with good planning and taking these factors into account, you can greatly increase the efficiency of your PV system. Adjusting tilt angles and optimizing south-east-west orientations can achieve a lot. When planning, pay close attention to whether your designer has factored this in.

How much electricity does a 10 kWp PV system produce in winter?

The fact that output is lower during the winter months is undisputed. In the winter half of the year (October to March), about 20% to 30% of the annual production amount is generated. Thus, the majority of production falls into the summer half of the year (April to September). However, this does not mean that a PV system is not cost-effective in winter.
Using the following formula, you can roughly calculate the yield of a PV system in winter or on a monthly basis:
Yield= Irradiance* Module Area* Efficiency

Let us work through an example:
Take the location of Klagenfurt in Carinthia, with average monthly solar irradiance:

• Solar irradiance in December: 18 kWh/m2
• Solar irradiance in January: 28 kWh/m2
• Solar irradiance in February: 48 kWh/m2

PV system output: 10kWp
Size: 50m2
Efficiency: assumed at 19%

December: 18 kWh/m2 * 50m2 * 0,19 = 171 kWh
January: 28 kWh/m2 * 50m2 * 0,19 = 266 kWh
February: 48 kWh/m2 * 50m2 * 0,19 = 456 kWh

Together, around 893 kWh are produced during the months of December, January, and February. This allows you to cover a significant portion of your electricity needs.

How should a PV system optimized for winter be oriented?

A PV system specifically optimised for winter should be planned with an east-west orientation. It is divided into two arrays, with one on the east side and the other on the west side of the roof.
The PV modules should also be installed more steeply than usual (55 degrees instead of 30 to 35 degrees) to compensate for the lower position of the sun.
This would be a system optimised purely for winter. Naturally, this alone does not make sense over the whole year, which makes comprehensive system planning all the more important for achieving maximum yield.

Conclusion!

Yes, the output of a PV system is lower in winter than in the summer months. Nevertheless, a PV system pays off even in the colder months. Using your own PV electricity is always cheaper than buying expensive grid electricity. Summer production is also many times higher than your self-consumption needs, allowing you to feed surplus electricity into the grid and receive compensation. We have already published a dedicated guide on this topic. Read more about surplus feed-in.

To benefit even more from your self-produced electricity, using a battery storage system is recommended. This increases self-consumption to between 50% and 80%, further reducing the share of purchased electricity.
A new and very interesting option is participating in an energy community. Find out what this can mean for you and the benefits it offers here.

With that, we have cleared up another cliché.
Are you ready for the next step? Follow the link to our interactive inquiry form and request a free, non-binding quote for your personal photovoltaic system today.