Common causes of underperformance and what you can do about them
Occasional underperformance is nothing to worry about and happens for a variety of reasons. In most cases, it's due to a difference between the sunshine and cloud cover that your system experiences vs. the weather that your nearest weather station experiences.
Another cause for slight variations in system performance may be due to extreme highs or lows in temperature, so variations are more likely in the depths of winter and the heights of summer.
What does Subpar mean?
Subpar means that your actual power generation was slightly lower than your estimated generation. There is a range of tolerance for this and beyond that range, you see a performance score that is rated as "Bad".
What does Bad mean?
A Bad performance score means that there was a significant difference between the power that you generated and the estimated generation of your system.
What can I do about it?
For underperformance which is either subpar or bar, one-off or infrequent, there's usually nothing that you need to do as this is most likely due to the weather, which, despite our best efforts, we can't do anything about either! Due to higher weather variability, the chance and impact of weather differences is higher in winter than in summer.
Seeing one bad or subpar day is usually nothing to worry about. Keep an eye on your Solar Sentinel and have a look at the "week view" (screenshot below on the right), which will show you a summary of each week. This is helpful for spotting trends and one-offs more easily
If you're seeing consistently lower figures, it might be worth a quick visual inspection - take a look at the panels to see if there is anything like bird poo, dust, leaves or tree sap.
Remember; if your panels are all on the same string (connected on the same wire) and you don't have any optimisers, any coverage or obstruction on one panel will limit the effectiveness of all the panels on the same string. You can either wait for the next shower to wash the obstruction away, or if it looks stubborn, get the panels washed, which should cost around £250 and will only really be needed every 2 years.
What if I'm seeing lots of Bad scores or zeros for my actual performance?
If you're numbers for your actual generation which are significantly below the estimated performance, as outlined above, you can check to see if the panels are being obstructed in any way, including if there is any shading.
If you're seeing zeros from your system or your visual inspection doesn't yield any results, then your next port of call is to check that the inverter is still working and that isolators and safety switches are still "open". Check out our troubleshooting guide on inverters here.