Round-trip efficiency is not the only variable at play here. Storage plant longevity, self-discharge over very long periods of time, cost of installation and ma

Round-trip efficiency is not the only variable at play here. Storage plant longevity, self-discharge over very long periods of time, cost of installation and maintenance, cost to the environment to source the raw materials etc also play a big role. Round trip efficiency might be way less than any other method of storage, but it might win out on all the other points. I don't know the answer though - just saying it's important in discussions like these to not get hung up on single metrics. We're not playing trump cards.