Electricity has no future in aircraft until the storage issue is sorted. The shear energy density of combustible fuels is orders of magnitude greater than the best (read very very expensive) storage solution we current have.
Specialist airframes - such a self launching gliders - can use what we presently have - until the cells get old and then their replacement costs make overhauling a Lycon seem like small change.
It all looks a very long way off unless there is a major break through in storage technology.
As for converting a Cessna 172? Why on earth would you pick that airframe for a technology which is challenged on payload, endurance and power?