I currently have a Payne AC unit model PA10JA024-A I have searched and could not find what size unit this is, my best guess is that it's a 2 ton unit but not sure. The only numbers I could find are the follow MBH-22.2, EEER-9.10, Seer-10.00, and HV-50-11.09 If I remember right this AC unit is approximately 6 or 7 yrs old and has not given me any problems to date but when I had this installed I am guessing that this was sized to cool my downstairs only as I did not have any heat runs upstairs. Looking at those numbers for this unit they seem to be pretty good given the size and age of the unit compared to the Carrier 25HNA6 that I most likely will have installed should this current unit take a dump on me in the near furture. The Carrier HP has a eer rating of 11.5 compared to the Payne that I currently have which is 9.10 given that there is only 1.40 in eer ratings between the 2 is this alot as far as eer difference goes. My current unit is a 10 seer with the Carrier having up to 16 seer which I know with this rating there is a huge difference. With these 2 units what would the appoximate savings I might expect if I were to go ahead and change the Payne out for the Carrier, and with the Payne I currently have running with my new Infinity 3 stage furnace to heat and cool apporximately 1500 sq ft. just off the top of your head is this AC unit enough to handle the sq footage I have to cool now that I didn't have when it was first installed ?