That depends on the capital expense of the fuel plant. If it's a high percentage of the fuel cost, then it needs power 24/7. On the other hand if energy is the

That depends on the capital expense of the fuel plant. If it's a high percentage of the fuel cost, then it needs power 24/7. On the other hand if energy is the dominant cost, then it's best to take cheap low-cost energy and shut down fuel production other times. That would apply in a nuclear grid as well; you could keep your nukes running 24/7 and run the fuel plants when demand is low.