There are probably not one general solution that will work everywhere. But for example in Sweden where about half of the electricity already is from hydropower,

There are probably not one general solution that will work everywhere. But for example in Sweden where about half of the electricity already is from hydropower, it will work well to even out seasonal variations, from for example getting very little sun in the winter. But say for California, where there’s enough sun most days of the year, generating hydrogen might work better to even out the electricity generation between night and day.