I have received 2 quotes on a new furnace for my 2 story wood frame colonial with 22 windows. Cold air returns on 1st floor only.

total sq.ft. - 1780
exixting furnace - 115,000 BTU Carrier Comfortmaker 80% single stage burner / blower. Date of installation 1987.

reason for new furnace - high fuel bill, cold spots and generally cold house.

contractor #1 - measured entire house, duct work, cold air returns and windows, then spent 3 hours going over calculations and units avail. And came up with the following information.

old unit is sized to big for my house and recommends 90,000 2 stage burner, variable speed blower with humidifer - Goodman make installed with standard mfg. warranty. Cost was $6,888.00

contractor 2 - looked at existing unit said it was sized wrong and in 20 minutes had a quote and recommendation of what we could use.

60,000 to 80,000 BTU with the same features recommended by # 1. Went with the 80,000 unit because he said that the 60,0000 would work to hard but could be used if I choose.
Goodman $3,500 - installed
Trane $4,500 - installed

why would there be so much difference between the two contractors and the size of units recommended?

I would say that contractor one is right be cuase he performed heatloss caculation on the house but is over priced
Contractor two is probably not right because he failed to perform heatloss calcution and probably used a rule of thumb

Check this