Well, no this is incorrect. Watts are joules / second, so watt * hours cancels time on both sides, it's just energy. Watt-hours are more convenient than "raw"

Well, no this is incorrect. Watts are joules / second, so watt * hours cancels time on both sides, it's just energy. Watt-hours are more convenient than "raw" joules only because we tend to be more interested in how many hours a battery will last at a given wattage, not how many seconds it will last. So energy capacity is correct, it's the amount of energy (not power) one can store in the battery. Edit: I read this as though you were replying to me, not the comment I was replying to. Swimming upstream, I see that, yes, "energy storage capacity" isn't in watts, but rather watt * hours, but I agree with @renewiltord that it's easy to understand once you factor in that journalists, for the most part, never took physics. The numbers have the units next to them, after all.