You can't keep chickens from going over a fence with hotwire. Really really.
And if I'm misunderstanding and your intent is to keep them from sticking their heads *thru*, hotwire is a dangerous and very ineffective way of doing that. Use smallish mesh (even STRONG plastic mesh is ok) for that.
The only way to DEFINITELY keep them from going over a fence is to put a top of some sort on the run. If you can't or don't wish to do that, then your best bet is to make the fence as tall as possible (absolutely no less than 4' but 6' will work better, though they can still easily get over that if they really want to) and when you put a horizontal rail near the top of the fencing, don't put it AT the top of the fencing but a foot or two lower down. That way they can't see the top of the fence real well AND can't very easily go up to perch there and then fly down outside. Clipping wings can also help. But if they really really want out, probably none of the above will do it. There is no good way I know of to predict how hard they will try to get out, although the larger and more-interesting and less-crowded the run is, and the less bored they are, they better; and bantams and small breeds (aside from silkies of course) are generally better fliers than large fowl breeds.
Good luck, have fun,
Pat