In any given month, a major utility in the eastern US faces an annoying problem. Hundreds of small generators send it money.
That's not how things are supposed to work. Usually, the utility pays generators for the electricity they produce, which is then distributed to the utility's customers. But when generators bid in a negative power price, which has been happening with increasing frequency, they can end up paying the utility. The utility's books aren't set up for that, and it has to find a wo