That won't end humanity. My propane generator from 1980 still works and I have plenty of fuel in a tank. This is enough to cold start generation of the grid. (the power company won't need my generator - they have their own plans to cold start, but worst case they can fall back to mine). While a hacker unstopped could do a lot of damage, most of the parts will still be functional and we have more than enough engineers to figure out how to bypass the areas they can take out. It might mean a few years of power rationing while the parts AI can break are repaired, but we can restart.