KenNeedham In my case with an offset E/W split I went for a guestimate of (kWp / 2) + 45% as a starting point.
That gave me, with 7.9kWp evenly split, a 5.7kWp staring point. Tweaked it up to 6kWp for Wonder Watt and it was pretty good in the summer. The over cloudy days of late messed that up. However, the improvement in the forecasting looks as if it has helped.
If you use Solcast and use their two site tool, (OK if you are a Givenergy user, not sure about Growatt) you will have a benchmark to compare against.
