For every $6.50 in energy savings that you save at today's mortgage rates, it means that you can afford $1000 more home or upgrades in your current home. Using the bankers rule of 72, even with an eight-year simple payback on an energy saving choice, 8 divided into 72 gives you a 9 percent return on that investment. That 9 percent return is a gain over the 6.5 percent mortgage money you borrowed. WIth that kind of return, you cannot afford not to invest in energy savings.
This information is from Alliant Energy's Connections Publication for Wisconsin of Summer 2007