That still doesn't require bidirectional communication. The power company can assume that a collection of a reasonable number of households will have a fairly p

That still doesn't require bidirectional communication. The power company can assume that a collection of a reasonable number of households will have a fairly predictable power draw when presented with information from the power company, and this should allow the power company to balance the surplus without receiving data back from the households. There're two issues here. The first is coordination - a lot of people might say that all they want the power company to tell them is the spot price and then let them make their own decisions on when to use power, and that anything more (such as instructions to different households to do their heating at a certain time) takes away their autonomy/sovereignty. That could be something that we just accept as a price to pay for a stable power grid, but it's more than we have now and I can see possible pushback against it. The second issue is price fairness - in the absence of another coordination method, a power company could manage demand by giving a lower price to groups of households to trigger the demand in a subset of the grid, so not everyone gets the same price at the same time. But they would have to do that in a fair way, for instance by time-sharing that lower price around.