That’s an interesting idea, because it matches the physics of the situation pretty well; on-demand capacity costs the grid something just to have it (batteries, or whatever), so it would be good to make that price visible to users and let them decide if they need it.

It might also push people more toward smart-grid tech, which is a desirable outcome. You might pick a dishwasher that can actually help shave the peak, if it saves you money.