Re: Principle vs Practice
We've had a lower-tech version called Economy 7 for decades, and even though I'm not on it, I find it convenient to run the dishwasher overnight when energy is (or would be) cheapest.
Unless you have more than 40% of your 'leccy use in the off peak period then you are worse off on E7. About a third of E7 customers can't do that, and you see tightwad pensioners like my dad spending a fortune on timers, but as he hasn't got storage heaters he's actually worse off. And when you stay the night the whole bloody house erupts at 02:00 as every appliance thunders into life.
Curiously, E7 looks to me as though it is only economic if you have both storage heaters and bugger all insulation, which was certainly true for most 1970s towerblocks. If the property has decent insulation chances are most people would be better off using them in on-demand mode.