(Mississippi Gulf Coast)
I recently purchased a high efficiency two stage heat pump, TXV, 1600cfm blower and ComfortNet thermostat for $8,100.
It also included replacing 50% of the existing duct work and the duct work was necessary because one side of the home was not cooling properly.
The central air conditioning unit includes a manufacturer lifetime warranty on the outdoor unit and contractor provided 10 year parts/labor on the entire central ac system.
Other proposals from the same contractor:
Trane XLi15 - $9,500
Trane XR13 - $5,700
Note: The local utility gave me a $300 credit for upgrading to high efficiency system. The central ac system also qualified for the $1,500 federal tax credit.
Bottom line: $6,300 for a 18 SEER unit.
Location: Mississippi Gulf Coast