Solar + Storage comes of age

In a recent article, flow-battery company VIZn says that it's now possible to pair solar plus storage in order to sell energy through a Power Purchase Agreement at US$0.04 per kilowatt-hour while reaping a 7% Internal Rate of Return (IRR).  Although this assume subsidies through Investment Tax Credits, it is a significant turning milestone: according to Lazard's Levelized Cost Of Energy, this is cheaper than coal at $0.06 to $0.14/kw-h and even cheaper than the cheapest combined cycle gas generation at $0.048 to $0.078/kw-h.

As an investor, which would you put money into: a solar + storage plant, or a combined cycle gas generation plant?