At a certain level it actually does matter. The sustainability of a power resource is measured in many ways, even if CO_2 emissions is the most widely touted. M

At a certain level it actually does matter. The sustainability of a power resource is measured in many ways, even if CO_2 emissions is the most widely touted. Measures like water use, construction cost/emissions, and land use are significant. The number of windmills being built _does_ have an upper bound, dictated by some combination of land requirement and material availability. Of late, for example, the desire for high-output synchronous turbines has been held back by the limited availability of the rare earth magnets that make them just so effective.