i posted the Q having a gut feeling that a formula would not have enough factors to exist.
some power companies have more detail than others, probably due to thier metering methods.
The Q came from a 6 unit building, 200A service, 6 meters w/ mains.
A service upgrade , to any given ampacity ,would then be done by getting some figures to work with from the power co. ( I got a peak billing month of approx 5500KWH )
and appling 220-35-1 which would be the maximum demand data avialable for a one year period) I have, in the past, recieved "peak" and "normal" figures , due to the metering methods as mentioned. I find this to be the most realistic approach.
not my first choice, thirty service calls , one for every day of the month? Let's tack on after hour charges, as that's peak usage.
220-32, optional calculation for multifamily dwelling,,,
( electric heat went out with disco around here)
Back to part B of art 220,
run a tape measure
don't let the cat out
my dog don't bite....