I wonder is a customer a single power meter or is that one building?
It’s a building, all of the subway lines, and these are counted as but ONE customer; it’s NOT a “person”!
A “customer” can be a single billing meter that can have 2 to 20 plus submeters sending pulses to it.
Electric utilities count customers by BILLING meters, that’s how their customer information systems are set up.
A single home can be one customer. A 10 MW skyscraper can be one customer.