Could power an underground town with one of those. Could come in handy if you needed to shelter in Mammoth Cave for five or ten years.
Or, instead of a cave. An abandoned mine.
I mean, we must be increasingly on the alert to prevent them taking over other mine shafts space, in order to breed more prodigiously than we do. Thus, knocking us out of these superior numbers when we emerge! Mr. President, we must not allow a mine-shaft gap!
Or a Moon base or a Mars base.