Realistically Im not sure there's much you can do. I recently had this happen to me, and all it took was for me to wash the paw prints off my hood, and it's never happened since. Then again, I put my car in the garage everynight (that's right, I actually use my garage for its intended purpose). But maybe you live in a high feline populated area. In which case maybe a friendly talk to your neighbours who own cats would be appropriate. "electifying" your hood, i'm guessing, is not only dangerous and mostly impossible, it is also quite cruel.