Well, that of course depends on whether you're talking about monetary efficiency (for which time shifting of large loads to lower night time rates makes monetary sense currently) or actual electrical efficiency (clearly needing a ton of work to properly improve upon).
Ultimately the latter is better, but there is so much nuance involved that I don't expect it any time soon. I personally believe that anyone interested in pushing the true efficiency envelope should be looking at getting the most out of off-grid systems right now, at least until more promising innovations show up within the grid itself.
It's not effective right now because we have a grid built upon the assumption that demand and supply are relatively static.