3 Ton 18 SEER 96% AFUE 100,000 BTU Goodman Gas Furnace and Air Conditioner System - Downflow Review 2026

// Bottom Line

This Goodman system works best for homeowners replacing aging equipment who prioritize upfront savings without sacrificing efficiency ratings. The 18 SEER cooling and 96% AFUE heating make it solid for moderate climates, though real-world performance depends heavily on proper installation and ductwork sizing.

Review

The Goodman 3-ton two-stage system sits in a competitive middle market where efficiency meets affordability. At $89 for the condenser unit alone, this represents the equipment cost only before installation, ductwork, and the matching furnace component. Online Supply positions it as an Energy Star qualified option targeting contractors and homeowners tired of single-stage efficiency penalties but unwilling to spend $15,000 on premium brands.

Performance numbers tell a practical story. The 18 SEER rating and 35,000 BTU cooling capacity suit 3-ton applications in moderate climates, while the matching furnace delivers 100,000 BTU heating output at 96% AFUE efficiency. The two-stage scroll compressor runs at 71 dBA, quieter than single-stage alternatives during partial-load operation. Variable-speed ECM blower technology supports up to 2000 CFM, enabling better dehumidification during shoulder seasons when cooling demand drops.

Pros & Cons

Pros

18 SEER rating qualifies for Energy Star certification, reducing cooling costs compared to older single-stage units
96% AFUE furnace efficiency means minimal heating fuel waste, especially valuable in cold climates with long winter seasons
Two-stage compressor and burner provide part-load operation, running quieter at 71 dBA during mild weather conditions
Variable-speed ECM blower motor adjusts output from 0 to 2000 CFM, improving humidity control and comfort consistency
R410A or R22 refrigerant compatibility offers flexibility if you have existing line sets from older systems

Cons

Product listing shows conflicting tonnage specs: title claims 3 ton but specs list 5 ton, creating uncertainty about actual capacity
Downflow-only configuration limits installation flexibility in homes with basement or crawlspace furnace placement
71 dBA noise level is noticeably louder than premium models with sound dampening, potentially noticeable in quiet homes

Who Should Buy

Best For

Homeowners in moderate-to-cold climates replacing 15-year-old systems who can absorb installation costs upfront. Contractors managing mid-range residential projects where efficiency rebates matter and customer budgets sit around $4,000 to $6,000 for complete system installation.

Consider Alternatives If

Anyone needing a single-stage budget unit should look elsewhere, as should those with attic-mounted furnaces requiring upflow configuration.

3 Ton 18 SEER 96% AFUE 100,000 BTU Goodman Gas Fur

$89

Buy at HVACDirect →

Installation

Downflow configuration requires installation in an attic, closet, or utility space above living areas with adequate clearance for the 34.5-inch height and 28.75-inch depth. Sweat connections demand a competent technician for refrigerant line brazing. Plastic PVC exhaust flue meets current codes and costs less than metal alternatives. Electrical requires 115V single-phase 60Hz service with 21.3 to 35-amp breaker capacity.

Warranty & Reliability

Ten-year parts warranty applies with online registration, covering compressor, coils, and components. Registration is mandatory to activate coverage, so document your purchase and serial number immediately. Labor coverage is not included, meaning repairs after year one require service technician fees. This warranty depth matches mid-range competitors but trails premium brands offering 10-year labor protection.

Specifications

SKU	LS38783850
Brand/Manufacturer	Online Supply
Cooling BTU	35,000
Heating BTU	100,000
Refrigerant	R410A or R22
Electrical	115 V. 1 Phase 60 Hz
Warranty	10 Years with Online Registration
Decibel Level (dBA)	71
Weight (in lbs)	30.000000
Feature	Spec
Product Features	Rebate Available
Energy Star	Yes
SEER1 (Efficiency)	18
Condenser Stages	Two Stage
Compressor Type	Scroll
Liquid Valve Size	3/8"
Suction Valve Size	3/4"
Max Breaker Size	35 amps
Min. Breaker Size	21.3 amps
Tonnage	5 Ton
Valve Type	Sweat
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 AdobeÂ® AcrobatÂ® 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	7/8"
Style	A-Coil
AHRI Certificate Number	7368844
Airflow Direction	Downflow/Horizontal
Exhaust Flue Requirement	Plastic / PVC
Furnace Efficiency / AFUE	96%
Blower Motor	Variable Speed - ECM
Maximum CFM	2000
Burner Stages	Two
Fuel Type	Propane, Natural Gas
Suction Line Insulation Thickness	3/4"
Length	50 feet

Frequently Asked Questions

Does the 18 SEER rating actually save money compared to older 13 SEER systems? +

Yes, approximately 28% annual cooling energy reduction in moderate climates. A 13 SEER system cooling a 2,000 square foot home costs roughly $1,200 annually in cooling alone. This 18 SEER unit reduces that to about $860, saving $340 yearly depending on local rates and usage patterns. Payback typically occurs within 8-12 years through energy savings alone.

Can this replace my existing 3-ton unit with minimal ductwork changes? +

Possibly, but verify your current ductwork handles 2000 CFM maximum airflow without excessive static pressure. Older homes sometimes have undersized ducts causing efficiency loss. Have an HVAC contractor perform static pressure testing before purchase. Downflow configuration requires attic space, which some homes lack, creating installation complications.

How does 96% AFUE furnace efficiency compare to high-efficiency condensing units? +

96% AFUE is excellent, approaching top-tier efficiency without the complexity and cost of 98% condensing models. You'll recover 96 cents of every dollar spent on natural gas or propane as heat. The remaining 4% escapes through the flue, which is negligible compared to older 80-85% AFUE systems still operating in many homes.

Is Goodman equipment as reliable as Carrier or Lennox? +

Goodman owns the same parent company as Carrier and uses similar engineering standards. Real-world reliability depends more on installation quality and maintenance than brand prestige. This model's 71 dBA noise level and scroll compressor design are proven technologies. Budget models sometimes cut corners on components, so verify your contractor uses OEM parts during service.

What does the 10-year warranty actually cover if something breaks? +

Parts coverage only. Compressor, coils, refrigerant circuits, and blower components are covered for manufacturing defects. Labor, service calls, and refrigerant are your responsibility. Registration must be completed within 30 days of installation to activate coverage.

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