It pays to read as much as one can, as widely as one can, about "green" energy alternatives. It's a hot topic, and shameless hucksters will present a dramatic statistic and not be forthright about how it applies to one's microclimate.

For instance, my state has very inexpensive electricity. The carbon dioxide emissions from electricity production per kilowatt hour in our state is 0.25, compared to the U.S. average of 1.34 (for years 1998 - 2000). Electricity costs are $25/month for us. Natural gas is more like $80/month. Several alternative energy suppliers may make much of the savings in energy, but if I'm spending I'm hoping the window replacement will take care of some of this. As I opened my natural gas bill, I did read an insert from my utility offering rebates (up to $300 or 50% off) for additional energy efficiency measures like duct sealing and insulation, floor/attic/wall insulation. Taking advantage of the rebates will reduce the payback time, and increase the internal rate of return. If an energy efficiency measure performs better than 12% a year, it makes sense for me to choose it over traditional investment vehicles.

We're consuming 55% - 70% of what the average family consumes in energy, in our antiquated house, but I think we can do better. I'm aware of the law of diminishing returns, however. I just don't recognize the savings until there's a 10% reduction in cost or energy use on my bill. Since the same period last year, we haven't seen a reduction in either.

Book information
The Carbon Buster's Home Energy Handbook: Slowing Climate Change and Saving Money, by Godo Stoyke.
New Society Publishers: Gabriola Island, BC, Canada; 2007.
Website Carbon Busters