"If the grid is 100% based on a conventional energy system with some combination of reliable coal, gas, and nuclear sufficient to meet peak power demands for the geographic coverage of the grid, then to install even a single wind generator or solar panel becomes an "overbuild" that makes no economic sense. Thus the only reason that renewables can possibly make sense is when the government subsidizes or mandates them (and allows utilities to pass the higher costs onto customers), but if the utility still needs to maintain near 100% reliable power system capacity for backup when the wind/sun isn't available it is still "overbuild" and can only increase system costs to customers."
Firs paragraph from E Olson comment at the Manhattan Contrarian website:
Sealing The Coffin Of "Renewable" Energy May Take A Few More Nails — Manhattan Contrarian