What are you heating with? I might have missed it. Propane or natural? Propane is kinda expensive these days and you can heat with strip heats almost as efficiently depending on where you are. I'm at the other end of the spectrum. I'm in Texas. It was 92 today. You need to look at the amount of insulation in your home as well as sealing it up as best as you can. No amount of efficient hvac can lower an energy bill as having your house insulated. Big bang for you buck IMO.