I think this is the easiest thing an average homeowner can do that rewards you the most - both through monetary savings realized and from the satisfaction of knowing you are in a quieter, less dusty, warmer/cooler home when you want it.

With this insane inflation, it also is one investment that arguably will pay for itself multiple times over. It is estimated you lose 5% of your heat in a home JUST FROM THE PLUGS AND LIGHT SWITCHES ALONE.

(http://www.autoadmit.com/thread.php?thread_id=5758476&forum_id=2Vannesa#49157699)