Which furnace is cheaper to run?

The 97% unit. At 97% AFUE it turns about 97 cents of each gas dollar into heat, versus 80 cents for the other. On a $1,000 annual gas bill that is roughly $170 a year saved, which pays back the $460 price gap in under three years.

Can I replace an old 80% furnace with the 97% one?

Only if you can run PVC intake and exhaust pipe and a condensate drain. The 97% unit condenses, so it cannot use a standard chimney or B-vent. The 80% unit drops into an existing standard vent setup.

Which one is better for a cold climate?

The 97% unit. It delivers 85,000 BTU of output versus 64,000 BTU, and its modulating valve holds output low and steady instead of cycling on and off.

Is the 97% furnace worth the extra $460?

Yes if you plan to stay several years and can handle the venting change. The efficiency savings and steadier heat usually recover the difference. If you are selling soon or venting is hard, the 80% unit is the practical pick.

Both are heavy-gauge steel furnaces with ECM blowers and similar service life, typically 15 to 20 years with annual maintenance. The condensing unit adds a heat exchanger and drain system that need yearly cleaning, so it depends more on install quality than on brand.

Do either come with a propane kit?

No. The 80% unit needs kit LPM-06 and the 97% unit needs kit 68W77, both sold separately. Budget for the kit if you heat with propane.

80,000 BTU 2-Stage Gas Furnace vs 88,000 BTU Modulating Gas Furnace 97% AFUE

Buy the 97% modulating furnace if you plan to stay in the house and want the lowest gas bills and the steadiest heat. Buy the 80% two-stage furnace if the upfront price matters more and you already have a standard-efficiency vent setup. The 97% unit costs $1,229 at Surplus City as of November 7, 2026, versus $769 for the 80% unit at Surplus City the same date.

Today the 80,000 BTU 2-Stage Gas Furnace costs $460.00 less at its best price.

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