My biggest reason for buying window inserts was for sound. I live in a neighborhood with lots of children, and after they were installed, I was able to relax, read or watch TV without any distractions. Also, a tree had fallen and broken one of my windows this year. Not only did the soundproof window insert keep the broken glass from coming in to the house, it kept all of the rain out too. As far as the energy savings, they have paid for themselves many times over.