I feel like I'm overwiring a smaller place when I put in more than 2 or 3 230 V general purpose circuits (or maybe even 1 in a studio apartment) and 2 appliance circuits (dishwasher and washing machine)...
Recently I wired a large-ish condo (4 bed 1 bath) with 14 circuits... boy that felt like overkill! 7 in the kitchen alone, 150 m (almost 500') of flexible conduit for the kitchen renovation.
With 230/400 V you can get by with a rather small number of circuits in an average household.
Supplies aren't awfully large in Vienna either. Well into the 1970s 25 A 1ph was common (5.5 kVA max. load) and even today anything exceeding 35 A 3ph (roughly 24 kVA) is rare. On the other hand, the electric range is usually the largest load, followed by the dishwasher (those go up to 3.5 kW). AC is highly uncommon, except for the occasional portable, mini-split or window unit, all of which are content with a 16 A 1ph circuit (230 V 2w 1ph).
For feeder sizing, code requires 18 kVA per unit (electric cooking, gas or other hot water and heating) or 22 for a "fully electric household" (electric hot water). I think electric heating supplies have to be calculated according to the actual load.
If you cook with gas, you can even get by with 20 A 1ph in old places, although you'd better avoid running washing machine and dishwasher at the same time. Still more than the measly 15 A you get in Italy!
