Thinking about upgrading from traditional to tankless with your water heater? The Rinnai web site
has a calculator that shows the return on investment and 20-year life-cycle costs.

Looking for the whole enchilada? Home Energy Saver promotes itself as the first web-based do-it-yourself energy audit tool. If you dig deep enough, you even can see your home's annual carbon emissions and learn how to cut costs and curb pollution.

Nifty!

With so many free tools to provide facts and figures about beefing up insulation, upgrading windows, or going with Energy Star appliances, home buyers should have no complaints about the initial investment of going green.

(Oh, and if you happen to also run a swine farm, check out the U.S. Department of Agriculture's Energy Tools website and see how much juice you could save by altering your tending methods. Pigs in a blanket, anyone?)