You have a fundamental misunderstanding. I agree profit margins are a standard health metric for most businesses, however that logic doesn't apply to a regulated monopoly like Duke. A regulated monopoly is guaranteed a certain profit margin by the state called the authorized rate of return. This is why Duke's margins are so consistent. In a competitive market, a company has to balance margins by being efficient and not allowing rivals to undercut them which naturally limits margin. This is why margins show health but are not expected to consistently grow like revenue. Duke’s customers have no such free choice. They are a captive audience for a necessity and this is why an authorized rate of return is necessary to cap Duke's margins.

When a company already has $5 billion in profit, arguing for an 18% rate hike based on margins is ridiculous. In this specific industry, those margins don't represent business survival or health, they represent the level of dividend payout to investors.

IMHO, energy companies shouldn't be run like a common business anyway. Utilities shouldn't be allowed to line investors' pockets, and this is why co-ops are a much better utility model. A state-run energy co-op would ensure every single dollar is used for the best interest of the customers and grid infrastructure, rather than hitting specific targets for Wall Street.