I would like to install a geothermal heat pump system. My house sits upon granite rock. If I have a vertical hole drilled 150 - 450 feet down, would there be any pros or cons to drilling in rock versus soil base for thermal release to heat pump system? In other words, would the system work better in rock or soil to heat my home?

Geothermal can work in one of two ways:

1. An intake and a discharge well some distance apart
2. A closed loop system where pipes are buried in the ground.

You may have only choice #1, but you need two wells. And now you have to worry about the contaminants of the water and heat exchanger corrosion.