Stephen,
You have precisely, if we can use the term in this context, conceived of the cacko condition.
You start with an assessmennt of the number of windmills required to achieve an arbitrarily established M Wattage (not to be confused with, or necessarily segregated from, the misundertood M theory in physics, or M Butterfly in theater, although there certainly was some Heisenbergian flavor to M Butterfly, not that Warner was anything like J Edgar Hoover, and Warner is all over that String stuff, but I digress).
But you must impose upon the equation several cacko factors.
First, the availability of wind. This quickly becomes cacko-fractal when you try and average the available windage and determine how big of a representative coordinate system will be used. The bigger the coordinate system the more homogeneous (no, we ain't back on M Butterfly or J Edgar)the number becomes, though it also becomes more inaccurate.
Now, as your illustration makes perfectly clear, a butterlfy's wing in Brazil (ala Edward Lorenz) can certainly add some Heisenbergian uncertainty to the survival rate of operating windmills, and therefore a cacko-fractal-chaos factor must be imposed.
Now given that we have only touched the tip of the iceburg with factors we can immediately surmise that the cacko-fractal-chaos factor system becomes cacko-fractal (and if the a Labor Union gets involved Chaos) itself. So we have a tiered Emergance/Supervenience factor (ala G.H. Lewes).
By the time you resolve the cacko-fractal-chaos-emergence equation you end up saying 'scrooo it', lets go back to coal.