California is already experiencing it, and it’s now the “new normal“:

Fast-forward to the early spring of 2014. The California Independent System Operator (CAISO), due in part to an unexpected abundance of solar generation in what was supposed to be the rainy season, had to institute curtailments of wind and solar power coming into the grid on four separate occasions. In one instance, more than a gigawatt of combined wind and solar power was curtailed, a condition that the grid operator calls over-generation or “overgen.”

There are three options to deal with the problem of renewable over-generation:

1) Store the surplus energy in energy storage technologies like batteries for later use,
2) Export it to other states, or
3) Encourage ratepayers to delay using electricity until this surplus becomes available.

California is trying to encourage all three options, and we’ll need them all to address the problem.