The first 3 days have been very sunny and have produced a total of 26 kWh. This seems disappointing and doesn’t suggest the system will achieve the promised results over the year.
Clearly shading from the trees is a major factor. The attached montage shows the shadowing against the output (on the main inverter only since the smaller one does not have a display) for each hour, plus 10.30 as the point where the output suddenly improves.
These results then sent me back to the original documentation from Ardenham Energy. The output they promised in their proposal letter was 2,448 kWh/annum. Whereas in the document sent after the commissioning this has gone down to 2,004 kWh/annum. Why such a significant change? This would seem to be a reduction of about a fifth in what we were expecting for the quoted price.
Ardenham’s reaction was very helpful. They looked into it and found that their original quotation had omitted consideration of the shading factor. Since we were not getting what we had paid for, they made a really good offer – to change the inverters to the newly developed ones when they become available. These prevent the shading of one panel pulling down the output of the rest, so should restore our promised annual output to 2,448. These new inverters will be available in August, so we shall see.