There is also the energy ROI to consider: if it costs more to make the stuff that generates the power than the power produced over the lifetime of the stuff is worth, it's a negative ROI. Example: let's say that a wind generator costs $500,000 to produce, but over its lifespan it will produce only $450,000 of electricity. Or if a technology, say a solar panel, costs 15,000 "energy units" to produce but only pays back 10,000 "energy units" you have expended more energy than you have gained (and probably added to the pollution problem in doing so).

Look at fusion. It would produce ample power AND use the current nuke waste for fuel (it can use ANYTHING for fuel). But the US Gov. shut down the fusion energy projects just as they were starting to show some promise...the R&D was felt to cost too much.