The “smart grid” we are working towards does things like scheduling your AC and dishwasher to turn on/off depending on supply and demand fluctuations. To that e

The “smart grid” we are working towards does things like scheduling your AC and dishwasher to turn on/off depending on supply and demand fluctuations. To that end, every node, both consumers and energy producers, needs to be connected. To do this completely independent from the existing internet would amount to doubling the cost of our communication infrastructure. It would also defeat your purpose, because suddenly everyone on the grid has access to the network again, and could try to attack it. You also need some connection, somewhere, to the “regular” internet. As just one example, consumption data is the basis for billing, which needs to connect to financial infrastructure. And, finally, even air-gapped systems are vulnerable. See Stuxnet.