[arethuza]

Still pretty small compared to pumped storage - they give a value of 20 megawatt-hours, the Cruachan pumped storage scheme (which isn't particularly large) stores 7.1 gigawatt hours:

https://en.wikipedia.org/wiki/Cruachan_Power_Station

[ashtonkem]

For comparison, the liquid air battery in this article is rated at 250mWh.

[arethuza]

I assume you meant Mwh? :-)