[NickM]

A typical iPhone battery is on the order of 10 Wh. An iPad is more like 40 Wh. If you add up all the iPhones and iPads in the world, the combined battery storage is probably on the order of tens of GWh.

If the load shifting that this feature enables lets us avoid building out a proportional amount of utility-level battery storage, that is a pretty non-trivial savings in money and resources. A single GWh of utility-level battery storage costs on the order of half a billion, so the return on investment for coding a feature like this into iOS is probably pretty good.

It's not gonna save the world on its own, but it's still a nice win.