They also assume a wide grid and overcapacity, which balances it out. And their storage capacity is minor, and they assume relatively cheap backup power. Like I said, there are plenty of things wrong with it, but it's nothing like what is wrong with the OP.

It doesn't invalidate their findings, it means they understated their case - thought I think that is what you are saying too.

(Also, http://www.theretheyretheir.com/. Not usually a grammar Nazi, but that's pretty hard to read)

Battery cost are projected to drop significantly over the next 5 - 10 years.