Geothermal systems are the most efficient heating and cooling systems available. They use a small amount of electricity to heat and cool your home by utilizing geothermal energy readily and freely available in the ground. In other words, in summer the heat is removed from your house and dissipated in the ground, and in winter, the heat from the ground is brought into your house.
We have installed a geothermal system in our new house about 2.5 years ago, and we are very happy with it. While it costs about 40% more upfront for a complete installation (including duct work), our entire enegry bill for our 3, 200 square feet house averages about $135 a month, including lights, appliances, television, etc. Also, most electricity companies give reduced electric rates of roughly 50% normal cost for houses with a geothermal system.
Geothermal is a forced air system that can be easily installed in pre-existing gas furnace installations. It can be used in any latitude.