yes, I can shed some light and will.
first the answer to the question--- CLOSED SYSTEM... less maint. for starters.
With Geothermal, generally in our area (SD) its sized for the cooling load rather than heating. Many things can play a factor in its payback and customer satisfaction.
1. location- in town with high electric/gas rates its very attractive, out of town with low electric rates it will take a bit more to get ROI
2. Wells- Don't let anyone jive you here (life blood of the system) 99% of installers use a rule of one well per ton of equip. 3ton=3 wells. we sell standard lengths of wells @ 210 I say again 210 its is the most efficient depth in our area... deeper may cause better heating but lack the cooling, and shallower just the opposite. (actually trench loops are supposed to be the most efficient, but not the norm).... Also be carefull who does these wells, and antifreeze in the system is crucial (correct ration) and also thermo conductivity of grout put in the well will greatly increase/decrease its efficiency.
3. equip- Again, often sized for the cooling size it will ensure comfort in the summer, as you don't have supplement cooling other than other units. But with heating you can (and often will as stated earlier) use your electric strip heat when its get brass monkey cold for awhile. Keep in mind you can do many things with a geo unit ranging from just simple heating and cooling to water to water systems,,,,meaning all your infloor heat, domestic hot water, swimming pools heck many options here.
I have known people that take the leap and are very happy and see extreme savings and others will take longer to get the ROI...
Some name brand gas/LP units are saying these new 20+seer and 95% effic units are just as good.... but the deal is,,,, EVEN IF SO
. you still don't fork over your wallet every month for the fuel as the water is just being recycled in a geo unit....
well sorry about rambling,,,, can field other questions if needed.....