Without a doubt, electrical sensitivity is genetic because human beings are not meant to be coursing with electricity in their bodies. Even small amounts of electricity can harm the human body in various ways, and most people feel great pain while being electrocuted. We're not meant to be around electricity.
To one degree or another, electrical sensitivity is show in many animals, even humans. The best examples is when birds or other creatures can tell when a storm is coming, mostly because of the electircal fields generated by the events, and there are analogous sorgans and mechanisms in humans, even though not as strong.
Yes, I believe that electrical sensitivity is genetic, because sensitivity to electrical things is caused by the body's reaction to a stimulus. A person cannot help if they are sensitive to electrical stimuli. There are scientific problems that are involved that cause a person to react that way. Two people often react different to the same thing, not just in electrical things, but in science and life in general.
I do not believe electrical sensitivity is genetic. Prior to our recent times, humans didn't interact much with electricity outside of getting hit by lightening. I believe it is environmental because its really hard to classify it as something inherently wrong with the person that experiences it. I've had minimal experience with it and while it caused some headaches, it didn't do much else.
Electrical sensitivity is probably environmental because without electricity, there is nothing to be sensitive about. There may have been a time when someone go too close to a strong EM field and it disrupted someone's nervous system. Perhaps a person's body was already sensitive in general and electricity just exacerbates another problem. I can't see someone getting this disorder from an ancestor because without the presence of electricity, you can't determine whether or not someone has a sensitivity to it.