You're just making the "we're going to have an energy surplus" case.

We already have storage technologies that could compete with present-day energy prices if charging them was near-free. They're currently not competitive because it isn't, but in your scenario during off-peak it would be. So why would anybody have to reduce consumption then? Buy a battery, charge it when power is dirt cheap and use as much as you do now for no more than you pay now.