Freshwater station with 500-liter buffer storage

No, that is not possible because I do not live in the house myself. By 1 person I meant my mother, and I cannot put her through a complete renovation towards a heat pump with insulation measures, enlarging the radiators, etc.

No, you're probably right there. Maybe take a look at the domestic hot water heat pump then? An additional benefit would be that you wouldn't have to start the pellet stove in summer, which isn't worth it for such small tanks and probably uses as much electricity as heating all the water with the heat pump. That way, the heating system also lasts longer. And a cheap model should cost less than the fresh water one.

Yes, I will try that with the domestic hot water heat pump or a mini pure electric WWB