[wexler88]

It's true that hydrogen is more practical for storing energy for months, but I think that storing energy for a few hours each day between daytime and nighttime (and transporting it from hot, sunny states to freezing, dark ones) is the important problem to solve.

[adrianN]

You need to solve both problems to reach 100% renewables, but doing in the order of demand side improvements, short term storage and then long term storage is probably the cheapest way to proceed.