Every other picket.
Surprise!!
How about this: Odd pickets get electrified on odd days, even pickets get electrified on even days. Just for shits 'n giggles, every once in awhile we electrify it all. Just for the hell of it and just to keep the hispanics guessing.
Only electrify the top 1/4 of it to make it harder for them to steal the copper.. for that matter go ahead and make the top of it transmission line voltage and sell electricity generated in Texas to California, with a surcharge that can be used to fund the wall, electrical generation, and transmission costs... there, its paid for and keeps paying for itself...