You're correct, but in the industry we really just talk in terms of Power at the transmission grid level and usually in millions of watts or MW. So if a coal plant is currently generating 2000 MW and you have a battery that can only consume 5 MW or 0.25%, then that isn't very much storage. Put another way, let's say the load in your region is 60 GW and you have 200 MW of energy storage. That is only a tiny fraction of storage relative to what the demand is.