Is your system only underperforming during Autumn and Winter?
During Autumn and Winter the path of the sun in the sky is much lower than in summer and spring. As a result trees, electricity poles, antennae, chimneys and other buildings and structures cast long shadows – which means your solar panels could be copping a lot more shade.
The takeaway: If you are receiving alerts in winter to say your site is underperforming, and you can see a sustained drop in production through the winter months, it is most likely due to winter shading. Rest assured it will resolve itself when the sun reaches a higher zenith later in the year, or if you can remove the shade-casting object.
See the image below for a system on a Sydney home that is severely impacted by shade during winter.
The grey part of the graph in May, June, July and August over the two years is when large trees to the north blocked the winter sun from reaching some of the solar panels, reducing the actual (yellow) production dramatically. In summer the trees do not cast any shadow over the house.
Solar Analytics’ performance calculations are unique – no other monitoring service can calculate your system’s expected versus actual production.
In the example above, the expected production is lower in winter (due to lower sunshine hours in winter) but the actual production is much lower than expected because of the winter shading.
We are constantly improving the accuracy of our algorithms and we are currently working towards being able to show the impact of winter shading as ‘lost to shading’.
If you are receiving alerts in winter to say you have underperformance and you can see a sustained drop in production below what is expected, it is most likely due to winter shading.
You can rest assured it will resolve itself when the sun reaches a higher zenith later in the year, or if you can remove the shade-casting object.