We don't necessarily need 100%, just enough to allow rolling blackouts to even be an option. In Austin, they had to turn off power to ~40% of all customers pre

We don't necessarily need 100%, just enough to allow rolling blackouts to even be an option. In Austin, they had to turn off power to ~40% of all customers pretty much as soon as the shortage began. Once they had done that, they could not implement rolling blackouts without also affecting critical infrastructure like hospitals (the granularity of the electrical grid is finite, apparently). The result was that some people had power the whole time (or nearly so), and others had nothing for ~3 days straight. Obviously it would be preferable for everyone to have intermittent power 1/N of the time than for 1/N to have nothing at all for the duration of the shortfall.