This kind of thing is actually a real problem from a grid stability point of view. The unpredictability of wind and solar and the lack of a way to store their output effectively make dealing with these intermittent renewables challenging (and a thorn in the side) for grid management. Due to the way electricity dispatch markets often work (http://www.eia.gov/todayinenergy/detail.cfm?id=7590), base-load style power plants (e.g. coal, nuclear, etc.) end up not being able to run or even paying to run. This becomes a strong disincentive for the construction and operation of these plants that are vital for steady, dependable electricity supply. The market structure in addition to the regulatory environment in the U.S. (e.g. requiring utilities to purchase all provided wind energy at higher than natural market price) are both part of the problem. Cheap natural gas also hasn't helped. The Vermont Yankee nuclear plant closed due to energy prices being too cheap (https://en.wikipedia.org/wiki/Vermont_Yankee_Nuclear_Power_P...).
[edit] grammar and paste fixes