Ann: Quarterly Shareholder Update, page-11

I am not sure I understand the issue you have Anndy. As I am concerned the Energy which is being stored would otherwise be lost so I do not think your example matches that cause. 

IMO it is comparable to a Mobile data plan. If your plan offers you 5GB a month but you'd only spend 3,5GB the remaining 1.5 would be lost even though you'd have paid for it. Now your providers gives you the option to roll over 1GB a month into the next month you'd still loose 0.5GB but still had at least that 1GB extra instead of it being wasted as well. 

Point I'm trying to make is that a storage is not producing extra energy but saving it for a time when there is no production. I hope I made sense because indeed my preferred language wouldn't be English