Geothermal heat and cooling.
We're looking into using ground source (geothermal) for heating and cooling our home. This will take our heating and cooling costs way down!
My understanding is the most of the cost is upfront and that the system pays for itself in a short time... while we enjoy low heating/cooling bills for years and years and years!
This site talks about how it all works: http://www.geothermal.org/what.html
We had a gentleman come to our "work in progress" last week. Should get the estimate soon.