Which used published rates, on at published times which do not rapidly change.
This is very different from electricity prices that change unpredictably from one minute to the next.
At most we should have something like EDF's Option Tempo.
While those rates may be published, they do vary from area to area, as do the times at which those rates apply. The peak/off peak times are determined at a central location while local conditions may dictate that it's more peak in one area than another. A smarter system may be able to figure out that today is a total roaster in one part of the country and that everyone is at the beach, therefore if you happen to be stuck at home, now might be a good time to run the washing machine.
We don't all work nine-to-five, and we don't all sit and watch Corrie at the same time these days, so peak demand is far less predictable than it used to be. A system that can monitor an individual household's usage and offer a price incentive to lower demand at certain times might not be a bad thing.
Have your pricing structure, but also have the ability to offer discounts to encourage usage when there is less demand.