Really not required to have this much juice. You do know all 3 can be hooked up to a single 60a circuit right? they are rather smart as they regulate charge as required to each unit. Lets say you have 3 cars plugged in but 2 are fully charged, the third get the full capacity of the charger. If 2 cars need charging then they will both receive half the capacity of the charger. 1 car plugged in will get full capacity of the charger.
This is not true. The manual specifically states that each charger is on it's own branch.