The big cost for ground source HP, is the large area you have to dig with 4 foot deep trenches. I have seen one where the installer digs 2 trenches about 16 fee

The big cost for ground source HP, is the large area you have to dig with 4 foot deep trenches. I have seen one where the installer digs 2 trenches about 16 feet apart and 30 feet long down to 6 feet. They then use a soil drill to make about 50-60 holes between the trenches and insert 17 foot plastic pipes(1 inch diameter) They then connect the pipes on each side to a common pipe(3"), all well sealed ABS pipes below the frost line. This allow for a large volume of coupled and warm(55 degrees) that the heat pump extracts/deposits heat as needed for heating/cooling the home. This drilling is a lot cheaper than a dozen or more 3 foot trenchs for the water loops.