This reflects the amount of sun that fell on your area, based upon available weather information.
We take into account the weather (ie. overcast weather vs full sun) as well as the number of daylight hours at different times of the year. We then compare this last month to previous years to let you know if there has been any difference.
If the month is sunnier than usual, you should see more solar energy generated by your solar system. Similarly, if it’s less sunny than usual, your system will likely have saved you less than previous years.