I thought you generally read this thread and paid attention. Pipestrel has multiple planes in production which match the C172 or C152 for training flights. And they are not motor gliders, but designed from the ground up as an electric plane.The physics definition of efficiency is the output divided by the input. By that measure, the Cessna is not terribly efficient; nor are most TC GA aircraft.
But when one considers that a battery powered aircraft to replace that Cessna has not yet been put into production (except for powered gliders with wing spans that are problematic for many users), the Cessna’s “efficiency” at getting private owners into the air for pure pleasure with some CC utility is infinitely higher than the mythical battery powered replacement.
People who want to fly will, for the foreseeable future, be better served by purchasing a Cessna than waiting for a battery powered aircraft.