But I guess there is some upper bound of connected nodes, or covered grid area, where it makes sense to break the grid up into sub grids, and make those sub grids self-sustainable? E.g. voltage losses over huge distances would force you to transmit with high voltage to faraway subgrids, and require additional transformer stations; not to speak of the line losses. I think you could eliminate those by giving each node cluster (residential area) its own closed grid. Perhaps emergency needs (like a rock concert in your neighborhood) could someday be covered by long distance laser or EM transmission from other grids, without using a landline that makes power management so difficult (because when interconnected, all grids would have to coordinate their combined consumption).