But AI hardware is much, much more expensive than either of them. Clearly it's not acceptable to simply shut AI training off at night, so solar is not a complete solution.
cost curves suggest solar+battery will be cheaper than coal by the end of the 2020s, if it’s not already
You mean new solar+battery will be cheaper than new coal plants, yes.
This is a question of whether to turn old coal plants back on.
Renewable PPAs for AI compute would help bridge the gap.