If everyone had these and they were all attempting to "charge during nonpeak hours" wouldn't those hours become the peak hours?
Of course, that assumes that generation can be consistent. Right now, that is the case. If we took the existing grid and just gave everybody batteries, we could make power consumption flat throughout the day, which would greatly reduce costs. That would be cool!
The idea is that in the future, solar dominates. There you inherently have peak and non-peak hours, because you generate more electricity at noon than at midnight. This is completely impractical if you go straight from generation to use, because the times don't match up. But throw in storage to flatten it all out, and it works.