For instance, the flow of fuel oil in a pipeline could be considered as an energy current, although this would not be a convenient way of visualising the fullness of the storage tanks.
Against heavy resistance from the engineering community,[1] Heaviside worked out the physics of signal velocity/impedance/distortion on telegraph, telephone, and undersea cables.
[2] Building on the concept of the Poynting vector, which describes the flow of energy in a transverse electromagnetic wave as the vector product of its electric and magnetic fields (E × H), Heaviside sought to extend this by treating the transfer of energy due to the electric current in a conductor in a similar manner.
With this achievement of "unification", the energy current approach has largely lost favour, because in omitting the concepts related to conduction it has no direct model for (for example) Ohm's Law.
Poynting-flow diagrams are part of E&M engineering, transmission line theory, and antenna design, but rare in electronics texts.