Thanks for the replies. Maybe I didn't explain my question correctly. My old furnace is not a 2 stage 92%. It is a GE 120,000 Btu single stage. I have had an estimate for a replacement, and am considering the 92% 2 stage model. I live in Salt Lake City, have a "rambler" about 1400 sq. feet up and a finished basement about the same sq. footage. I added extra attic insulation a few years back and believe it is @ R22 now. The salesman based the furnace size on comparison to what I already had. Correct me if my assumption is incorrect. The sale catalog boast that you want a 2 stage furnace so it takes your home a little longer to heat up, thus more evenly. I figured that my old furnace, probably 60% AFUE, was putting out about 72000 Btu. If I went with a 100,000 92% at full power it would put out 92,000 Btu, and about 69,000 on the low stage. (75% of full). If I went with the 75,000 Btu I would have 69,000 at full and about 51750 at low. I figure that the 100,000 would most likely run on second stage most of the time and would think that if it ever kicked into high, it would peel the paint off my walls : -) But am concerned that the 75,000, even on high, would not be enough to heat the whole house. That's where my question comes in. Given these facts, do you think the 75,000 model would be enough to heat my home? Is the 3000 to 5000 Btu difference between what my old furnace put out and what the maximum (69,000) of the 75,000 could do? Thanks very much for your time.