Those two coal plants are only being run sporadically now, which probably means that they're being run as "peaking" plants, which is a very expensive mode of operation. A year or so ago TVA closed our local coal plant after replacing it with a natural gas one, and while they were at it they also built a one megawatt solar plant nearby. Which is all well and good, but that solar plant, even under ideal conditions, can only produce 1/1000th of the power that the natural gas plant can!

And just a couple of months ago TVA opened a 53-megawatt solar plant in my area, and they are promising that it will produce enough power to run thousands of homes plus some industrial-scale stuff. I haven't yet been able to find output stats for the two newest installations which I've already mentioned, but I have been monitoring a third local solar installation of basically identical design. And even under "ideal" conditions it's only producing 60% of its promised one megawatt output, and on average only a small fraction of it. (I don't know if it's always been that way or if the situation has deteriorated in the five years it's been in operation.) If TVA keeps building out solar plants which on average only produce a small fraction of their promised output, then before long they're going to be in trouble.

This is a general problem with wind and solar; they only produce a fraction (on average) of their "nameplate" (full capacity under ideal conditions) output, yet "nameplate" is what gets quoted in press releases and such. But actual average capacity may be only 25% of that (to use a ballpark number), meaning that you have to divide the quoted capacity by four to get a far more realistic capacity. Meaning that the 1/1000th number that I quoted above is probably actually more like 1/4000th!