Some of your questions read to me more like explanatory factors than confounding variables. If cost of capital is lower for public utilities, great, that’s an argument in favor.

I actually think the most interesting factor is listed down in the “about the data” section: “ Most of the gap opened from 2020 to 2023, during the energy price spike: 25% at investor-owned utilities, 11% at public utilities and co-ops. Before and since, both rose at about the same pace.”

So, it might be basically the same story everyone complains about. When there’s a shock, companies tend to quickly hike prices higher than they need to, but after the problem is resolved they’re slow to let prices come down again, if they do at all.

And that detail casts doubt on other explanations because if they were the case we wouldn’t expect to see the divergence be largely confined to the pandemic. There was still a gap before 2020, but it looks like it had been a fairly steady ~1¢/KWh.