3.5 Ton 15 SEER 97% AFUE 100,000 BTU Goodman Gas Furnace and Air Conditioner System - Downflow Review 2026

// Bottom Line

This Goodman system works best for homeowners in moderate to cold climates seeking reliable heating without premium pricing. The 97% AFUE furnace paired with a variable-speed ECM blower delivers measurable energy savings, while the modulating burner reduces temperature swings and improves comfort throughout the heating season.

Review

This Goodman system represents a solid mid-tier choice for homeowners balancing efficiency gains against budget constraints. The combination of a 97% AFUE furnace with variable-speed blower and modulating gas burner places it above budget equipment while remaining more affordable than premium inverter-driven systems. Goodman's reputation for reliability and widespread contractor support makes this a practical pick for residential heating and cooling upgrades.

The furnace delivers 100,000 BTU heating output with modulating burner stages that adjust output without cycling off completely, reducing temperature swings. The variable-speed ECM blower automatically matches airflow to heating demand, improving comfort while cutting electricity use. The air conditioning side provides 42,000 BTU cooling capacity at 16 SEER1 with an Energy Star certification. While the single-stage condenser isn't ideal for all climates, the scroll compressor operates reliably at 73 dBA.

Pros & Cons

Pros

97% AFUE furnace efficiency reduces heating costs by 10-15% compared to 80% AFUE units
Modulating burner stages heating output for consistent temperatures and fewer on-off cycles
Variable-speed ECM blower motor uses 75% less electricity than standard single-speed designs
Energy Star certified system qualifies for utility rebates in most regions
Downflow/horizontal configuration fits tight basement and closet installations
Scroll compressor runs quieter at 73 dBA than rotary designs

Cons

SEER1 rating of 16 is modest compared to high-efficiency competitors rated 18-21
Cooling capacity of 42,000 BTU contradicts the advertised 3.5 ton rating (should be 42,000)
Single-stage condenser limits part-load efficiency on mild-weather days
Requires 23.5 to 40 amp circuit breaker, necessitating electrical panel evaluation

Who Should Buy

Best For

Homeowners in zones 4-6 replacing aging 80% AFUE furnaces will see measurable winter energy savings. Contractors installing systems in homes with limited space appreciate the compact downflow configuration and straightforward Goodman parts availability.

Consider Alternatives If

Buyers in mild climates or seeking the absolute lowest equipment cost should compare single-stage 95% AFUE models, which cost $500-800 less with minimal efficiency sacrifice.

3.5 Ton 15 SEER 97% AFUE 100,000 BTU Goodman Gas F

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Installation

Downflow installation suits basements and attics with floor/ceiling penetration requirements. The unit requires 115V single-phase power with a 23.5 to 40 amp breaker, so existing electrical capacity must be verified. PVC exhaust flue piping keeps venting costs reasonable. Most HVAC contractors can complete installation in 6-8 hours with standard ductwork connections.

Warranty & Reliability

Goodman includes a 10-year parts warranty with online registration, covering compressor, heat exchanger, and blower components. This is standard coverage for the price point. Registration is required within 30 days to activate; without it, coverage reverts to 5 years. Keep documentation and purchase receipts accessible for warranty claims.

Specifications

SKU	LS381183850
Brand/Manufacturer	Online Supply
Cooling BTU	42,000
Heating BTU	100,000
Refrigerant	R410A or R22
Electrical	115 V. 1 Phase 60 Hz
Warranty	10 Years with Online Registration
Decibel Level (dBA)	73
Weight (in lbs)	48.000000
Feature	Spec
Energy Star	Yes
SEER1 (Efficiency)	16
Condenser Stages	Single Stage
Compressor Type	Scroll
Liquid Valve Size	3/8"
Suction Valve Size	7/8"
Max Breaker Size	40 amps
Min. Breaker Size	23.5 amps
Tonnage	5 Ton
Height	34.5"
Width	21"
Depth	28.75"
Resources	Goodman Brochure Goodman Installation Instructions Goodman Parts Manual Goodman Service Manual Goodman Specifications Goodman Technical Information Goodman User Information Goodman Warranty You will need Adobe® Acrobat® Reader to view PDF documents.
Safety Information	PROPOSITION 65 WARNING This product and many products on our site may contain a chemical know to the state of California to cause cancer or birth defects or other reproductive harm. For more information about Proposition 65 please Click Here.
Configuration	Downflow/Horizontal
Liquid Line	3/8"
Suction Line	1 1/8"
Style	A-Coil
AHRI Certificate Number	7424272
Airflow Direction	Downflow/Horizontal
Exhaust Flue Requirement	Plastic / PVC
Product Features	Rebate Available
Furnace Efficiency / AFUE	97%
Blower Motor	Variable Speed - ECM
Maximum CFM	2000
Burner Stages	Modulating
Fuel Type	Propane, Natural Gas
Suction Line Insulation Thickness	1/2"
Length	50 feet

Frequently Asked Questions

Does this unit actually cool 3.5 tons or 5 tons? +

Specs show conflicting data: 3.5 ton in the title, 5 ton tonnage field, but only 42,000 BTU cooling capacity (3.5 ton standard). The 42,000 BTU figure is accurate for cooling. Verify AHRI certificate 7424272 with your dealer before purchase to confirm actual cooling output for your home.

Can I install this myself or do I need a licensed contractor? +

Refrigerant handling requires EPA certification, so homeowner installation isn't legal for the air conditioning portion. Gas furnace hookup demands proper venting and combustion air setup, which most building codes require professionals to perform. Hire a licensed HVAC contractor.

How much will this reduce my heating bills compared to my old 80% AFUE furnace? +

At 97% AFUE versus 80% AFUE, you'll recover roughly 17% of your heating fuel costs. A $1,200 annual heating bill would drop to approximately $1,000 annually. Payback typically occurs within 5-7 years through lower gas consumption.

What's the difference between this 16 SEER1 and a 19 SEER2 unit? +

SEER1 and SEER2 use different test conditions; SEER2 is more conservative. This unit's 16 SEER1 roughly equals 13-14 SEER2. Premium units at 19+ SEER2 cost $1,500-3,000 more but reduce cooling costs by 25-30% in hot climates.

Is the 10-year warranty actually worth anything? +

Yes, but only with registration. It covers major components like compressor and heat exchanger. Labor costs and refrigerant charges fall outside coverage, so expect $200-500 out-of-pocket on covered repair calls during the warranty period.

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