The grid is profitable enough for the power comanies to invest in storage tech like this - http://www.gravitypower.net/ http://www.gravitypower.net/ - or this -

The grid is profitable enough for the power comanies to invest in storage tech like this - http://www.gravitypower.net/ http://www.gravitypower.net/ - or this - http://www.lightsail.com/ http://www.lightsail.com/ - which provide the grid response of hydro, but with the flexibility of being able to put it in at the local level. Now as to the question of centalised being more efficient, it is not at all clear, given transmission losses, if that is true with solar systems that have local storage.