This question is based on the presumption that Force Lightning, like regular lightning, is composed of electricity. I'm not sure about that. Every written description I've seen of the phenomenon calls it "dark side energy" or something similar.
I can't find any source in canon which specifically uses terms like "electric" or describes the lightning bolts as a flow of electrical current. Force Lightning is most consistently described as bolts of energy (which may be electrical energy).
That said, canon descriptions of Force Lightning use terminology which is related to electricity and electrical shock. For example, the Episode VI script describes the Emperor's final moments as:
Vader grabs the Emperor from behind, fighting for control of the robed figure despite the Dark Lord's weakened body and gravely weakened arm. The Emperor struggles in his embrace, his bolt-shooting hands now lifted high, away from Luke. Now the white lightning arcs back to strike at Vader. He stumbles with his load as the sparks rain off his helmet and flow down over his black cape.
Lightning is, of course, a type of electrical arc.
Additionally, the canon novel Lords of the Sith describes the Emperor using Force Lightning against a lylek queen as follows:
His Master raised both hands and sent a storm of Force lightning into the queen, enmeshing her in sizzling blue lines. She screamed and spasmed in agony, her mandibles parting wide to reveal the rows of her teeth as the lightning tore at her carapace and the organs underneath, burning her inside and out.
Lords of the Sith, p. 238
The Force Lightning causes the lylek queen to spasm, which is a symptom of electrical shock. For example, the Chicago Electrical Trauma Research Institute describes the effects of an electric shock as follows (emphasis added):
Compared to a high-voltage shock that usually is mediated by an arc, low-voltage shocks are more likely to produce a prolonged, "no-let-go" contact with the power source. This "no-let-go" phenomenon is caused by an involuntary, current-induced, muscle spasm.
Force Lightning is also described as "burning" the lylek queen, and this is likely an electrical burn.
There is no definitive statement that Force Lightning is electricity, but canon descriptions of it are highly suggestive that it is.
The effect it has on the human body isn't the same as electricity out of your wall socket, for sure. If Luke was getting shocked in Return of the Jedi by 60 Hz AC he wouldn't have been able to form a coherent sentence asking his father for help. His muscles would have been contracting beyond his ability to control his diaphragm.
If force lightning is still electricity, we can narrow down the details, at least. We're talking about a flow of charge carrying particles through the air and through the body of the target. But where is that charge coming from and going?
Is it flowing in a circuit, leaving the user and returning to him as in a DC circuit? If so, why don't we observe a return path? Is it flowing through the floor? If so, why is it not damaged? Or perhaps it's in one finger and out the other?
More likely it's AC, with no net flow of charge out of the user over time. The user must be one pole of an AC voltage source, with the other pole somewhere behind or inside the target. But then, if the user can manifest arbitrarily located voltage sources outside of their body, why does the other apparently have to be in his fingertips? Palpatine contemplates in one novelization how Vader's artificial arms prevent his use of force lightning. But maybe only one node has to be in the biological body of the user, and Vader's real limitation was the possibility of damage to his suit.
If this is the case, could lightning be harnessed for productive purposes? Use it to actually power electrical equipment? If so, how many watts worth? Can we know the horsepower of the Dark Side?
Or is charge permanently leaving the body of the user and building up as static elsewhere? That would mean the user and some other object are gaining net charge of opposite polarities. This would not normally be physically sustainable, creating a tremendous electrical field and voltage potential. The Emperor would essentially be one plate of a giant capacitor, with the dielectric being the Force itself. The mother of all static discharges will happen as soon as the user is not actively trying to prevent it. Maybe this is why the emperor violently exploded?
Or is the user summoning charge from nothing and returning it to nothing? Conservation of charge is one of the fundamental physical laws of the universe. If defying that was a possibility, the user of force lightning would have the ability to rewrite the very structure of any matter. I may not know the power of the dark side, but I think we can be sure that if the emperor could do that, we would have very different movies.
So if force lightning is electricity, based on Luke's ability to still speak, I think it must be AC of either very high or very low frequency. High frequency would tend to travel over Luke's skin rather than penetrate his body. But then, perhaps the Emperor manifested the remote voltage node inside Luke's body.
Perhaps I'm thinking about it wrong still. The sound of the lightning wasn't a single tone, but was a pretty broad frequency profile. I'm honestly not sure what that would do to a human body, but it's at least possible you'd still be able to speak. I still think the fundamental would have to be pretty high, perhaps in the low kilohertz... Has anyone done a Fourier transform of the sound of force lightning?
EDIT: Based on the sound effect linked in the comments, force lightning has roughly equal frequency content between 50 Hz and 8 kHz. I tend to think that Luke shouldn't be able to talk being shocked with AC at those frequencies. But I'm not aware of any definitive studies one way or the other. Still, based on the frequency analysis, I lean towards this not being electricity.
EDIT 2: I've learned more about electrical arcs. Current flowing through air releases tremendous heat. If this was really electricity, Luke would have been burned to a cinder just from the heat involved. He's basically being struck by lightning for a solid minute or so. Most arcs that kill people last a fraction of a second. The fact that Luke survives at all, not to mention the fact that the room doesn't melt around him, says this is not electricity.
The original novelization of Return of the Jedi simply uses the term "lightning" or "energy" in all but one single description of the attack. In this one instance, it describes electric currents coursing through Vader as a direct result of the Force Lightning.
Palpatine struggled in the grip of Vader's unfeeling embrace, his hands still shooting bolts of malign energy out in all directions. In his wild flailing, the lightning ripped across the room, tearing into Vader The Dark Lord fell again, electric currents crackling down his helmet, over his cape, into his heart.
I suppose it's technically still possible that this mystical hypothetical Force Lightning isn't really electricity and just somehow causing the electric currents in Vader's body, but if it looks like electricity, sounds like electricity, and shocks like electricity, at some point we're going to have to accept that it's most likely actually electricity.
I would speculate that it's a form of resonant energy transfer using the bloodstream to conduct the tiny high frequency electric charges in the midi-chlorians sort of like an electric eel. The problem is that it is very bad for cells causing induction heating and virtually cooking El Palpatino so is not used much. Also explains force powers being limited in both range and energy as energy source is potassium 40m3 which is an isotope that is astonishingly rare in our Galaxy. It decays under control of an enzyme which reduces trigger energy below the range of blue light rather than normal of 28keV