[iScience]

please confirm this for me: if i obtain hydrogen via electrolysis, wouldn't it make sense that the amount of energy i get out of burning the amount of H₂ i have would be equal to the kWhr of electricity i put into the system?

if not, why not?

if so, is there a problem with the practicality of this where one equals the other?

[Corribus]

Ideally, yes. But as you can expect, there are always going to be energy losses. The biggest losses will be from hydrogen transport, maintenance of equipment, loss of hydrogen, and side reactions. At the moment with current technology (particularly the transport and maintenance of equipment part) those losses are large enough that pure hydrogen is not yet a cost-effective fuel.

http://en.wikipedia.org/wiki/Hydrogen_fuel

[Arkcon]

if so, is there a problem with the practicality of this where one equals the other?

So, you can conceive of no practicality problems with getting exactly the same amount of energy out that you put in?  Like Corribus: said, there are always losses in transport and and transmission, so you want to ignore that, for the time being?  Sure ... but why?  What's the next point in the discussion?  Maybe you'd like to use electrolysis as an energy storage medium?  That is, perform electrolysis when energy is plentiful (i.e. solar cells in the daytime) and burn hydrogen when you need energy (to continue the example, at night.)  I suppose that's plauible, but since there are always some losses to side reactions, and wasted energy, why discount it, even for an academic question?

[curiouscat]

please confirm this for me: if i obtain hydrogen via electrolysis, wouldn't it make sense that the amount of energy i get out of burning the amount of H₂ i have would be equal to the kWhr of electricity i put into the system?

if not, why not?

if so, is there a problem with the practicality of this where one equals the other?

You'll have losses right at the start too. Electric heating of your wires etc.