I think where we are eventually going with half hourly slots priced according to demand could work out ok, but not with the current generation of smart meters, we need ones with an interface that allows pricing (and predicted future pricing to be accessed). That why you could set your electric car to charge overnight at the lowest rate possible but with the proviso that it must be fully charged by 7-00 when you need to leave, the fridge compressor could shut down for two hours at the evening peak if the door hasn't been opened and the electric car you have just parked up with 40% range remaining could backfeed into the grid during the evening peak, before it recharges later on.
We need to get to a point where demand can be matched to supply; renewable means are generally a bit sporadic in generation, we will need to meet the base load with nuclear generation, and these cannot be run up just when required, so controlling the supply to match demand is a little out of our hands, but demand could be matched with supply.
There was some work done on this about 15 years go looking at grid frequency, the loading of the grid could be judged from the frequency, a slowdown from 50hz to 49.95 foexample woud suggest its struggling to meet demand, where-as 50.05 might suggest there is plenty available, not sure if much ever came of what they did.
http://www.dynamicdemand.co.uk/
The hysteresis of it all would need looking at though, if the unit price goes down suddently, the demand would come online, and there would no longer be a suplus and the price would have to go back again, in which case all the loads decide to switch off again....