My heating A/C is 13 yrs old & not too efficient so I'm concidering a change. I'm looking at using a package unit heat pump or gas outside furnace with A/C. Can I expect the life & efficiency to be the same for a package unit as compared to a conventional split unit? Also, how easily can a ground source heat pump be retrofitted in an existing residence and can you give the approximate percentage increase cost over a package unit? I think my lot would be sufficient for burying the required length of pipe. I presently have