The largest US electric utilities are difficult to compare using company revenue alone because many holding companies own multiple regulated utilities, competitive generation businesses or gas networks. A customer-count view is often more intuitive for understanding the scale of the retail electricity franchise.
The Energy Information Administration collects utility-level customer and sales data, creating a consistent public source for comparison.
Holding companies can span several state utilities
Groups such as Duke Energy, Southern Company, American Electric Power, Exelon, NextEra Energy and Dominion Energy operate through regulated subsidiaries with distinct service territories and state regulators.
That means the parent-company name is not always the name on a household's electricity bill.
Generation and retail service are separate questions
A company can own a large generation fleet without serving the largest number of retail customers. Another utility can have millions of regulated customers while purchasing part of its electricity from wholesale markets.
The distinction is becoming more important as data-centre demand raises questions about who builds generation, who owns the grid and who ultimately serves the load.
EIA data make the ranking reproducible
Because utility customer and sales data are reported through federal datasets, the page can be refreshed with a clear methodology rather than relying on company marketing descriptions.
ACR will use this reference page as the corporate layer underneath its data-centre, grid and industrial-power coverage.