Here in Toronto the current standard for residential service is 200 A @ 120/240V (24 kW). Older homes might be 100 A. That would be the max that the conductor between the distribution transformer and the home's panel can handle without thermal failure. But you wouldn't size distribution transforms based solely on peak load because a mineral-oil immersed transformer has a lot more thermal mass than a cable and takes hours/days of sustained load to actually heat up. Average loads used for planning and distribution transformer sizing are more like 5-10kW/house.