One of my biggest pet peeves is when outlets talk about energy storage exclusively in terms of output and neglect to mention capacity. Does 15.7 gigawatts of storage mean 15.7 GWh? Capacity is as important, if not more important, than output.
As someone who's interested in all this, I agree it would be nice to have more precision around capacity. Especially as it relates to longer term storage. But! In this context, output is more salient than capacity. You'll see a lot of stories about grid-scale storage that use output. ( https://physics.stackexchange.com/q/854999 offers a fuller explanation than what I'll give here.) This is because grid operators are…
Some storage project list power output figures that can only be sustained for 90 minutes: https://en.wikipedia.org/wiki/Victorian_Big_Battery