[snowwindwaves]

A moderate distribution substation is probably more like 50 MVA.

A house with a 200A service at 240 V is about 50 kW. You might see a 250 kVA padmount transformer feeding half a dozen big houses but that is not the same thing as a substation.

[caf]

I have worked at an electricity utility. "Distribution substation" is the term of art for a 250KVA padmount transformer and associated HV and LV switchgear (or even just a 50KVA pole mount transformer). A 50MVA installation is what we would refer to as a Zone substation.

5KVA per residential lot is not an uncommon allocation rule. The network is simply not designed to supply every house 200A simultaneously (the same is true of water services: the maximum flow rate of your connection to the water main cannot be sustained if every house in your neighbourhood tries to consume at that rate).

[snowwindwaves]

We must live in different climates. Electric heat is common around here and a house can easily have over 10 kW of heat. An electric range gets a 50A 240V circuit (12 kVA). An electric clothes dryer has a 30A 240V circuit (7.2 kVA). All it would take to exceed 5 kVA per house is for everyone to be cooking christmas dinner on a cold night. Maybe somebody has a shower (electric water heater turns on) and then uses the hair dryer (1.5 kW).

Granted you can probably overload a transformer a fair bit on a cold night. I'll ask next time I'm talking to someone in distribution what their allocation rule is.

I feel like I'm used to seeing a 3 x 33 kVA cans feeding only a few houses (that incidentally had natural gas heat and hot water...)