We put in Geo-thermal in 2011. It heats and cools and is great. My husband estimated that it cost us $50.00 a month to heat this huge farm house this past winter; in the middle of Wisconsin. The house is well insulated and we have very large south and east-facing windows which bring in a lot of sunshine. That helps.
The Geo-thermal takes about a half acre of land (or you can go straight down, like a well), and cost us about the same price as a new car. At our age, we will probably not get the full return on this, but we like saving the earth.