  In a recent paper [A. Moujahid, A. d'Anjou, F. J. Torrealdea and F.
Torrealdea, Phys. Rev. E {\bf 83}, 031912 (2011)], the authors have calculated
the energy consumed in firing neurons by using the Hodgkin-Huxley (HH) model.
The energy consumption rate adopted for the HH model yields a {\it negative}
energy consumption meaning an energy transfer from an HH neuron to a source
which is physically strange, although they have interpreted it as a biochemical
energy cost. I propose an alternative expression for the power consumption
which leads to a {\it positive} energy consumed in an HH neuron, presenting
some model calculations which are compared to those in their paper.
