That's not how it works. I don't know the actual numbers, but what if peak load is 50% higher than average load? You need quite a lot of battery storage to make that work, especially if the peak load lasts longer than a few minutes (it usually does).
And that's true even assuming instant capacity adaptation. It's just not efficient to keep nuclear power at a capacity lower than their peak capacity.
And that's true even assuming instant capacity adaptation. It's just not efficient to keep nuclear power at a capacity lower than their peak capacity.