Wellhead Prices. Source: Energy Information Administration.
With a 30-year mortgage at 5% fixed APR, borrowing $1000 costs the borrower about $65 per year. An $1000 investment in energy efficiency (for example, upgrading wall insulation in a new home from fiberglass batts to a densely-packed cellulose) can generate $75 per year in heating and cooling cost savings, meaning the homeowner is better off ("cash flow positive") from Day One, even before considering the additional benefits below.
Insure yourself against future energy price increases.
No can say with any certainty where energy prices will be in 10 years (a reasonable time frame to consider energy efficiency investments), but I'd suggest that "higher than today" is a reasonable guess. Building a home that is inherently energy efficient is an excellent insurance policy against both short-term price spikes and long-term upward trends.
Be more comfortable in your home.
So, you've invested in energy efficiency and have a few extra dollars in your pocket. While some fret about rising prices, you are secure in the knowledge that your home uses much less energy than the great majority of the houses available today. And now, for the icing on the cake...you can walk on your wood floors in winter with bare feet, because your crawl space is insulated and conditioned. You can sit by the big west-facing window in the summer, because the window has a low -E coating that reflects the sun's radiated heat. In other words, your investment in energy efficiency, so often discussed in terms of dollars and cents, has perhaps its biggest payoff in terms of simple enjoyment of your home.
