Efficiency is not relative especially when it comes to mechanical movement. It is quantifiable data and nature does not care whether the energy is "green" or "clean". Energy is energy regardless how it is produced. Though the best data they can provide is the lift to drag ratio at cruise speed. This will give us a pretty good idea on how this aircraft performs.

Just be careful about how you quantify, the energy needed to overcome that drag ratio will presumably be delivered far more efficiently via electric moters, since they'll not be throwing 2/3rds of the energy away as heat.

So an electric plane could be twice as inefficient in other ways (e.g. extra weight for batteries) and still come out ahead overall. And that's before taking carbon and pollution into account.