C.C.
I own a construction company. Go back and read the quote he gave you. Did it say, "Time and materials, not to exceed..." or did it say, "Quoted price"? If it was a time and materials quote with a not-to-exceed amount, then yes, the actual time on site should be reflected in the bill. If it was a quoted job, and you agreed to the quote, then the bill stands regardless of how long it took him to complete the job.
Think about it this way. What if he had run into significant problems on the job, and it took a lot longer than he had originally quoted for, you certainly wouldn't be willing to pay extra over his quoted amount, would you? So why are you wanting money back because the job ran smoothly and he was able to finish quickly? He is not an electrician on a volunteer basis. Respect the fact that he did the work on time and on budget, and be happy with that.