Comment by ccalloway

There is a hierarchy of time availability of power supply:

  1. power available when you want it, and you can choose on the fly
  2. power available when you want it as long as you know in advance
  3. power available at a time that you don't choose, but you can predict
  4. power available at a time that you can neither choose not predict

Examples are (roughly) 1: gas or hydro, 2: nuclear or coal, 3: sun or tidal, 4: wind. You can also think of demand types that require each of these levels or better. Of course each of these categories contains its own sliding scale of how far in advance you have to decide or can predict. Wind is not completely unpredictable, but it is further down this hierarchy than almost any other source of generation.

Moving generation up this hierarchy, or demand down it, is always going to give some benefit. Well designed power markets should make sure that there is some fair incentive for any such step.