Hey Newchickmom,
Is the electric fence even set-up to deter this dog?? It needs to be at the right height and the right side of the fence. It sounded like this was originally intended for horses. Which makes me think that hot wire is maybe too high and on your side of the fence. Also, if the dog is a jumper, the fence may not help.
I like all of the suggestion on this post. They sound like great advice. I tend to use my airsoft gun to scary the neighbors dogs when they come sniffing around. Paintball gun is out of air, but I think it should send a messege back home. But, first you need a talk with the owners.
Oh, and the fences are high voltage and essentially use no current. They don't cost much to operate because you pay for power (voltage times current); no current = no power. That is, until the something completes the circuit. So, watch out for those shorts.
Jim