New construction with a granny flat - heating question and KFW.

I suspect the photovoltaic system offered by Bien-Zenker then powers both heating systems? it probably isn't really sufficient.

Anyway, in winter you always have to buy electricity when the sun isn't shining. And that happens quite often ;-) Oh yes, in summer, when the sun shines, you don't need heating (or only a little for hot water).