Cities can cost effectively start their own utilities

An enterprise, like providing a utility, has revenues and it has costs. The difference between the two can be called the "surplus labor value". What happens to that depends on the economic system.

In capitalism, capital owners own that enterprise (utility) and they siphon off profits raising the costs. Put another way, capital owners own the means of production, not the residents of the city or the city itself. This is rent-seeking behavior.

In a socialist organization of the economy, the residents either directly or through the city itself, would own the utility. Any profits would go back into the utility or be extra revenue for the city but there's really no incentive to increase prices on the citizens who own the utility (unlike the unquenchable thirst for increasing profits for capital owners).

I have to constantly point out that capitalism isn't markets (market existed thousands of years before it and exist in every economic system). Capitalism simply supplanted feudalism by replacing kings with billionaires. That's it.

We have abundant examples of how the latter is a substantially better system. Just compare EPB Internet (Chattanooga, TN and surrounds) vs Verizon, AT&T, Comcast or Spectrum. Municipal broadband, without exception, is substantially better than any national ISP. The only thing that keeps national ISPs in business is more rent-seeking behavior such as lobbying for legislation to ban municipal broadband.

Given this is the Superbowl weekend, it's worth adding that the Packers are owned by Green Bay (an arrangement the NFL now bans for any other franchise). What do we see in other cities? Teams extorating massive tax breaks from cities, counties and states to build massive stadiums at taxpayer expense without the team having to give up anything. The KC Chiefs are rumbling about leaving because the city didn't pass a sales tax increase to pay for upgrades to Arrowhead Stadium.

I don't know why anyone is surprised by any of this anymore.

Overall it reads like any other socialist argument for nationalizing (in this case "municipalizing") companies, which does not work both on theoretical grounds and based on historical experience. The claim "Walnut Creek could borrow from its utility in recessions, and loan money during booms" is laughable. We know how that ends: the city would finance its deficits with utility money until the company is bankrupt.

I do agree with your sentiment that city bureaucrats may be tempted to raid the energy business to pay for pet projects and other things. This can be protected against by segmenting the energy business into its own protected organization.