It already exists...
I'm in the process of switching to a tariff that's smart-meter based that charges 4.99p (per kWh) overnight, 11.99p most of the rest of the time, with the exception of 4-7pm on weekdays when it jumps up to 24.99p.
The reason being? I've just bought a Plug-In Hybrid car. So I can schedule it to start charging at 11pm and it'll be fully charged by 8am for a third of the price that I'd have to pay my current supplier. Or to put it another way, I'll be able to commute to work for less than 50p (whereas it was costing me £3 in diesel each way).
On top of that, I already have a smart meter, and was able to download usage from my current supplier at half-hour resolution as a CSV file. Whack it into Excel, couple of formulae, and worked out that with my current (non car-charging) use, plus proposed car charging use, I'd be over £200/year better off. Win.
So yes, they will save some people money - and as electric cars become more and more prevelant, it'll add even greater flexibility.
Biting the hand that feeds IT
