"Watt hour of storage" is not a unit, it's the physical quantity "storage" quantified by the unit "Watt hour", ie the combination of the two.

That’s what you’re not understanding. “GWh of storage” is a unit. It’s not an SI unit, but it is a unit, i.e. a thing you can use to measure something. The production of this factory is being measured in this storage unit. Watt is also a unit, a unit to measure power. There is no way to convert a unit of power to this unit of storage.

Do you have a reference for the definition of this energy storage unit? I have never heard of it before and my attempts at searching the web seem to contradict you.

Wikipedia writes: “Storage capacity is the amount of energy extracted from an energy storage device or system; usually measured in joules or kilowatt-hours and their multiples”

https://world-nuclear.org/information-library/current-and-fu... writes: “Storage systems for electricity include battery, flywheel, compressed air, and pumped hydro storage. Any systems are limited in the total amount of energy they can store. Their energy capacity is expressed in megawatt-hours (MWh), and the power, or maximum output at a given time, is expressed in megawatts of electric power (MW or MWe).”

Both of which to my layman reading opposes your claim.