Last summer when, for a while, I had several sheep in a temporary electric paddock on part of the lawn *and* six of the chickens were free-ranging during the day, they would go RIGHT THROUGH the sheep electric fence without thinking twice about it. This was the sheep electronet with the wires every 6" apart.
The thing is, chickens are feathery and lightweight and poorly-conductive, so they do not get zapped much by typical casual contact with an electric wire (obvioulsy if they get *stuck* in an electric fence it will severely affect or even kill them). So they just squirt right through.
If you want to keep chickens out of an area of garden or lawn, by far the simplest cheapest and most effective thing to do is to get a roll of regular ol' cheap garden netting and some bamboo stakes (or cut some straight thin saplings), and just string that up wherever you want. If the fence is at least 3-4' high and the top is not clearly visible, they tend not to challenge it unless they are Very Very Serious about wanting to get to the other side -- in which case even poultry electronet with a large charger on it wasn't going to keep 'em out b/c they can simply fly over if they sufficiently WANT to.
Good luck, have fun,
Pat