Remember this thing only stores energy. You still need the original source: coal, oil, nuclear.
Emphasis on the first and last, of which we either have plenty or can make it quickly (assuming the will do to so is present - watch the will develop overnight as gasoline climbs over $5/gallon). Also, don't forget natural gas, of which we also have a lot. Our neighbors to north & south also have lots of oil, and it cannot be a bad thing to provide more money to their economies (where will they spend their dollars?).