Pretty stupid, but interesting:
In theory, the Tokyo area could import electricity from the south. But a historical rivalry between Tokyo and the city of Osaka led the two areas to develop grids using different frequencies — Osaka’s is 60 cycles and Tokyo’s is 50 cycles — so sharing is inefficient.Short-term, energy efficiency will be the name of the game. Longer-term, it might just be best to integrate the grid.
There are transfer stations, but they have limited capacity. And the hand-off is comparable to two railroads that use different gauge tracks and have to unload cargo from one train and reload it onto another at the place the tracks meet.