Correct me if I'm wrong here, but as I understand it (told by a power
company employee) the speed of the meter spin depends on the leg with
the heaviest current draw. So if you have 60 amps on one leg and 20 on
the other, you pay for the 60 amp leg. Another reason to balance your
loads between legs.


You're wrong, here.

The meter is measuring the total energy consumed... not just one leg.

Some utilities will add an EXTRA charge on top of kWh, which would show up
on your bill as kVar. kVar is the difference in draw between the two legs.

Jake