I am assuming that you are referring to the reverse electrolysis as using the reaction like a battery.
Now lets say that we are to make a electrical circuit with a electrolytic solution. We will have a potential and we will cause a oxidation reduction action to occur as we run current through our circuit. We will also have some current that will generate resistive heat as it runs through this circuit and does not cause a oxidation reduction reaction to occur.
Now this system will only be able to give back as much chemical energy as we put into it. Both the charge and the discharge will release some energy as heat so we will get out less electrical energy than we originally put into the system.
The first law of thermodynamics states that we can neither create or destroy energy but since part of the energy is converted to heat we will always get out less energy than we put in.