Which heating system for the 200 sqm new building?

(2930 consumption minus 2108 feed-in) for electricity, water, and heating.

Are you sure about the numbers? For 2 people without heating, one usually calculates between 2500-3000 kWh per year. The controlled residential ventilation alone will consume about 100 kWh, and you even have an efficiency killer with a buffer on the underfloor heating. We have 6000 kWh for everything together (50/50 general/heating) and a significantly smaller house with 160 sqm. Although "only" KFW 55 and 24 degrees in at least 1/3 of the house, but also an air-water heat pump with an annual performance factor of almost 4.5.

2900kWh electricity consumption + direct and battery self-consumption does not seem unrealistic to me now.

We had 3800kWh without photovoltaics. 2000kWh household, 1400kWh heat pump, 350kWh controlled residential ventilation.

You also have it warmer in winter than thimHH in midsummer

The rest is taken care of by the photovoltaic system, and in our old apartment, the two of us only had an annual electricity consumption of 980 kWh. Apart from a significantly larger refrigerator, a bit more lighting, a WLAN repeater, and a robotic lawn mower, nothing else was added. The buffer tank on the air heat pump ensures that it always runs very evenly in inverter mode during winter. We have the smallest air heat pump in the series so that it operates at a good point. The ventilation consumes about 250 kWh per year. The basic consumption of the photovoltaic inverter is also considerable. But the photovoltaic system also had a yield of 3700 kWh (after storage, including feed-in), which fits the system due to orientation, inclination, and throttling because of KfW. We live here with three adults. Of course, one can discuss at length whether it makes economic sense for me, but environmental protection is not free, and the rest of the electricity we need, I buy from hydropower. However, I assume that household electricity consumption will rise a bit next year with children, but I am not panicking. More so afraid of a long, cold, dark winter...

nd battery self-consumption

Ah, that is included with KFW 40+, I hadn't considered that.

2900kWh electricity consumption + direct and battery self-consumption doesn't seem unrealistic to me now.

We had 3800kWh without photovoltaics. 2000kWh household, 1400kWh heat pump, 350kWh controlled residential ventilation.

You also have it warmer in winter than thimHH in midsummer

1400 kWh heat pump per year? Isn't that extremely low? That would be less than 300 euros in heating costs per year. I calculate 2 to 3 times as much, but it would be good if it's less.

Yes, it is very little, we have already optimized a lot during the construction and do not heat extremely high, and the winter was moderate. The coefficient of performance is just over 5, the heat pump is performing better than expected. It should not be a benchmark for others now, I had calculated about 2000 kWh before construction. 300€ is not quite accurate, we do not have a heat pump tariff and pay expensive green electricity, but finally the photovoltaic system will be installed soon.