It is not all about efficiency off the fuel production but also about fuel transport and storage. A wind turbine in Chile or on a remote island in the southern hemisphere can easily produce four times more energy than a wind turbine in Germany, but therefor you need a way to store and transport the energy (batteries are not suited for that). Also, the weight of the energy storage is important, if half of the weight is used for energy storage (see Alice) you need more energy for the same useful load than with a conventional propulsion system which might need aroud 25 % of the total weight.