You're looking for the biggest which isn't all that important. It's like saying you cannot deal with a difference in peak and through in production using a single power plant. For example, Norway has just 78TWh[1] in storage like that. Which is 2000x your example

And yes, I realize how well positioned Norway is for this. But you can put these wherever you have a stream and a big reservoir

1: https://energifaktanorge.no/en/norsk-energiforsyning/kraftpr...