If the question were simply one of efficiency, we would build a nuclear station or a series of gas fired stations. Since the former is not possible and the latter would increase our dependence on imported gas we are left with developing windpower to as large a scale as possible. In the context of having too much power when we don't need it and not enough when we do, pumped storage has to be considered as part of the mix and as such, it should be considered as part of the cost of large scale use of renewables. Again, the basic question is do we have sites which are suitable for pumped storage? Long before energy became a subject of popular discussion, the ESB investigated possible sites for hydro stations and pumped storage as part of their diversification program.