[jacquesm]

As long as the windpower installed reduces the need for baseline to be produced the efficiency can get pretty good indeed. No matter how high it goes this will not result in all baseline power generation being halted simply because it takes time to bring those plants online (shutting them down can go quite fast but ramping them back up takes time). Also, because of the inherent instability of renewables you always want to have a certain percentage of the current requirement available as non-renewable just in case.