Looks like the high-voltage transmission lines are very efficient, losing only a few percent over hundreds of miles: http://insideenergy.org/2015/11/06/lost-in

Looks like the high-voltage transmission lines are very efficient, losing only a few percent over hundreds of miles: http://insideenergy.org/2015/11/06/lost-in-transmission-how-much-electricity-disappears-between-a-power-plant-and-your-plug/ http://insideenergy.org/2015/11/06/lost-in-transmission-how-... There's a good watch on pumped hydro, and how it is kinda sucky: https://www.youtube.com/watch?v=66YRCjkxIcg https://www.youtube.com/watch?v=66YRCjkxIcg Battery storage is the most likely thing, although there is also kinetic storage (flywheels) and some other ideas as well (ultracapacitors, for instance).