Vehicle to grid, that makes sense to me. Car owners are going to be purchasing the batteries anyway and then using them <20% of the time. Might as well rent them out as long as the numbers work.

But I don't see homeowners purchasing several thousand dollars of batteries just to store some power in case the grid goes down. It's going to me more cost effective to establish large industrial scale storage.

We’ve got about 25GW of storage in the US, mostly pump-up along with a small amount of compressed air (CAES). It was built to ‘time shift’ electricity created by nuclear reactors from off-peak hours to peak demand hours. (We never seem to include the cost of that storage when we talk about nuclear.)

What we’ve done in the past to deal with supply/demand differences is to largely use dispatchable power sources. Hydro is very dispatchable, it can be turned on and off very rapidly. Next in line would be gas turbines “peaker plants” which can go from dead stop to full power in 10-15 minutes. And even coal plants can be ramped and down to some extent to meet demand.

With wind and solar becoming larger players we will need some storage to even things out. But not a lot for a while. Right now the US grid is fed by over 30% hydro and natural gas. They can fill in gaps when the Sun isn’t shining and wind not blowing. Once wind and solar get to be major players (>25% for the East Coast grid and >30% for the Western grid) we’ll need more storage.

Building some now is a good idea. As we build we tend to learn how to do the job cheaper. Getting storage to the point where it is cheaper than natural gas generation would be a great thing. One more way cut the flow of CO2 into our atmosphere.