I am having a hard time deciding on which system to use to replace my existing 2.5 ton HP that is 14 years old. Average electric bill over the last 123 months is $70.66. The minimum is $48.67 and the maximum is $116.00. Note: the few times that my electric bill is over $100.00 is during the heating season and not the cooling season.
Both of the new upgrades will replace the existing Air Handler with a new Variable Speed Air handler model.
Location is Rock Hill, SC. Single story house (1333 sq ft). Design conditions for the load calculation are: Winter Outdoor Temp: 10, Summer Outdoor Temp: 100, Winter Indoor Design Temp: 72, and Summer Indoor Design Temp: 76.
Loss/Gain Summary. Loss: 35791. Gain: 25479. using a Capacity Multiplier of 1.05 the recommendation was for a 2.5 ton single stage HP system with a variable speed air handler. SEER : 15.0 and HSPF 9.0.
A second recommendation was made for a 3.0 ton 2 stage/single compressor HP system also with a variable speed Air Handler. Note: different Air Handler for the 3 ton system. This 2 stage system runs at 70% capacity in stage 1. SEER 17.0 and HSPF 9.20. Note: a 2 stage system at 2.5 tons is not available.
The 3.0 ton system costs $$$ more than the 2.5 ton system. Now the contractor admits that the 3 ton system will not save me that much more money than the 2 ton system. The contractor does say that the 3 ton system will provide a better, overall comfort level than the 2.5 ton system.
Two stage HP seem to fairly new so my question is: Are there really any advantages to 2 stage systems vs. 1 stage system. Or is this nothing but marketing hype. They key point for me is will the 3 ton running at stage 1 be able to do the the job - say 85% of the time. If I end up running at stage 2 the majority of the time I would be better off with the 2 ton system because then the 3 ton system will be over sized. Am I correct in my thinking?