Hello,
as already mentioned, an energy demand calculation would not be a bad idea to roughly estimate what you would need.
Personally, I would be rather critical of an air-to-air heat pump – in my opinion, these pure air heating systems only work really efficiently in [Passivhäuser].
It is different with an air-to-water heat pump – we have personally had very good experiences with this – in combination with a [photovoltaik-Anlage], we should probably achieve very low heating and hot water preparation costs already in the first year.
Regards,
Dirk