Earlier quoted context omitted.
There is no such thing as "excess electricity". If that power wasn't being wasted on useless cryptocurrencies, then we could have used it for useful purposes, such as processing aluminum.
That's simply not true. When supply outstrips demand it's generally going to waste anyway. Doesn't California actually pay Arizona to offload their surplus energy?
Otherwise you'd ruin a lot of machines depending on either 220V/110V or 50Hz being on the grid.