At some point it has to be wasted. No one is going to built something that will use the last 1 hour of energy in a year that isn't assigned to anything.

Most factories have a stable running value. I.e. when they run they run at 100%. Capital is wasted when that investment isn't making money. So to have something that can absorb all excess is very difficult.

There will be some projects that ramp up and down. But it would be low capital cost high energy cost and I'm not sure what they would be. There might be some projects that also run for 6 months of the year. But even then I still see some waste happening