Gas Furnance 120000BTU

Faced with the same situation 2 years ago, I oped for a new 96% efficient furnace and 18 seer AC unit. I've never regretted it. It will take a few years to recover the ~5k it cost at a few hundred per month, but as energy costs escalate, maybe not so long. The main thing is that the house is more comfortable at less cost per month. As to maintenance on your old one; if you have central air, the coil in the furnace plenum probably needs cleaned and that will seriously restrict air flow. Also use the cheap filters, the expensive ones are too restrictive, jut buy a case and change them once a month

Not enough information. What is too Btu much in Georgia will freeze your ass off in Toronto. Type of house? Insulation? location? Construction?

goto heatinghelp.com and click on "questions" along top menu bar. It will get you to "the wall". These guys are very knowledgeable in questions along your line. Good luck, Tom

On the coldest days in the winter, how much of the time does your current run? I believe about 75% is a reasonsible amount. Furnace btu ratings are the energy of the gas used. A more efficient furnace will put out more of this heat. For example if your old furnace was 60% efficient it would put out 72,000 btu/hr. Likewise a new 90,000 btu/hr 80% efficient furnace would put out 72,000 btu/hr. These are ball park estimates. See what several contractors say.

Post your Q's to the Ask The Professor. The main part of the Wall is for boiler related stuff.