The way that power companies "communicate" about load is by slightly changing the frequency.
If the frequency is 60.5, then there's an abundance of energy on the grid and some less profitable generators can cut back or storage systems can charge. If the frequency is 59.5 then there's a lack of available power on the grid and other generators should go on line and unnecessary load should stop doing its thing (and if it has the ability, it could discharge instead).
I'm trying not to be smug, but are you under the assumption that the delivery of physical forms of energy is simple? Distributing, on average, ~1.5B liters of gasoline, with different qualities/chemistries/regions/etc, every day in the US has immense amounts of complexity. Now do that for coal, natural gas, heating oil, etc.
Managing time of day for charging isn't a more complicated problem than any of those.
The way that power companies "communicate" about load is by slightly changing the frequency.
If the frequency is 60.5, then there's an abundance of energy on the grid and some less profitable generators can cut back or storage systems can charge. If the frequency is 59.5 then there's a lack of available power on the grid and other generators should go on line and unnecessary load should stop doing its thing (and if it has the ability, it could discharge instead).