Rare prolonged outages are bad for batteries, since the capital cost is too high. You want something that has very low capital cost, even if it burns a fuel. Simple cycle gas turbines power plants might cost $0.50/W.
Existing battery technology works best when you don’t charge to 100% or discharge to 0%. On top of this you want oversized batteries to deal with battery degradation over time. This means any large scale battery system includes a buffer beyond normal use which you would only use if wholesale prices spiked.
On top of this grid operators want generation redundancy in case an individual power plant goes offline for whatever reason. Combining both you get quite a lot of excess capacity compared to the current grid.
Batteries sufficient for short term leveling would run out too quickly. If you build enough batteries for prolonged outages most of them would be unused during the leveling of short term fluctuations.
On top of this grid operators want generation redundancy in case an individual power plant goes offline for whatever reason. Combining both you get quite a lot of excess capacity compared to the current grid.