> Wouldn't there still be the OpEx of maintaining the power plants + power infrastructure (long-distance HVDC lines, transformer substations, etc)?
These are fixed costs. They don't go down if people use less power, so the sensible way to pay for them is with some kind of fixed monthly connection charge (e.g. proportional to the size of your service) or via taxes. You're still not measuring how much power people use at any given time.
Seems like the largest industrial customers would still need metered usage, though.
There are quite a few businesses that can scale limited only by power consumption — but due to that, they today need connections massively overbuilt compared to their current usage (as they project their usage growth to be extremely fast, potentially as much as doubling each year) in order to not need to be constantly re-trenching connections or browning out. Which in turn means that, under a leased-line electrical system, they'd be massively overpaying for unused power capacity at all times — possibly to the point of being unprofitable.
To achieve profitability, they'd need to negotiate billing based on only the fraction of the capacity of the available grid capacity that they're actually demanding on any given day... or, in other words, metered billing.
These are fixed costs. They don't go down if people use less power, so the sensible way to pay for them is with some kind of fixed monthly connection charge (e.g. proportional to the size of your service) or via taxes. You're still not measuring how much power people use at any given time.