There are two costs involved: installed (or capital) cost, and operating costs.

There are too many site-specific variables to quote a first cost for any given geoexchange system, but estimates to install a complete system (including ground loop and heat pump) range from $18,000 to $30,000 for a typical home. This may be higher than the cost to install combustion furnaces but in all cases, the drastically lower annual operating costs for a geoexchange system that provides space heating, water heating and space cooling, will be much lower than the cost to operate any other furnace of any efficiency level.  These much lower operating costs will allow the owner to pay off the unit relatively quickly - in some cases quicker than a traditional HVAC system - and then begin enjoying further savings for years to come.