How Much Does It Cost to Run an 80% AFUE Gas Furnace? - By Samantha Reyes, Home Comfort Advisor

👋 Welcome from Samantha Reyes

Hey there! I’m Samantha Reyes, your trusty home comfort advisor. One of the most common questions I get from homeowners shopping for a new furnace—especially an 80% AFUE model like the Goodman GR9T801205DN—is this:

“How much will it actually cost me to run this thing all winter?”

You’re not alone in asking. Energy bills can vary dramatically based on your location, furnace efficiency, home size, insulation, and thermostat settings. In this article, we’ll break it down with real numbers and tips for controlling your costs.

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🔍 What Does 80% AFUE Mean?

Let’s start with the definition.

AFUE stands for Annual Fuel Utilization Efficiency. An 80% AFUE furnace converts 80% of the natural gas it consumes into usable heat. The remaining 20% is lost through venting.

For every $1.00 you spend on gas:

• $0.80 goes toward heating your home

• $0.20 is wasted as exhaust

High-efficiency models (90–98% AFUE) waste less, but also cost more upfront.

External Link: For a more detailed definition, check the U.S. Department of Energy’s AFUE guide.

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🏠 What Factors Affect Gas Furnace Operating Costs?

Here are the major variables that influence how much you’ll spend running an 80% furnace:

1. Climate and Location

• Colder regions (Minnesota, Michigan, New York) will use more gas

• Warmer areas (Texas, Georgia, Arizona) will run the furnace less frequently

2. Home Size and Insulation

• A 1,200 sq. ft. well-insulated home will use less gas than a drafty 3,000 sq. ft. house

3. Thermostat Settings

• Keeping your house at 68°F instead of 72°F can cut bills by 5–10%

4. Natural Gas Prices

• Vary by state and season

• National average is ~$1.50 per therm as of 2025

External Link: Track prices by state at the U.S. Energy Information Administration (EIA)

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🧮 Sample Cost Calculation (Using the GR9T801205DN)

Let’s say you install the Goodman GR9T801205DN, which has:

• Input: 120,000 BTU/hour

• Output: 96,000 BTU/hour (80% AFUE)

• Runs an average of 6 hours/day in winter

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➤ Step 1: Convert BTU to Therms

1 therm = 100,000 BTUs

120,000 BTUs/hour × 6 hours/day = 720,000 BTUs/day

= 7.2 therms/day

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➤ Step 2: Multiply by Gas Cost

Let’s use $1.50/therm (U.S. average)

7.2 therms × $1.50 = $10.80/day

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➤ Step 3: Multiply by Days of Heating

Assume 4 months (120 days) of average usage

$10.80 × 120 = $1,296 per winter

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🗺️ Regional Comparison Table

 

Note: Costs assume a 120,000 BTU, 80% AFUE furnace running 4–6 hours/day.

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📊 Cost vs. High-Efficiency Furnace

 

👉 While the high-efficiency model costs more upfront, it can save ~15–20% on heating bills annually, and may qualify for rebates.

External Link: Check rebate eligibility on ENERGY STAR’s HVAC rebate page

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🧰 Tips to Reduce Gas Furnace Costs

Even with an 80% AFUE system, you can improve performance and lower bills:

✅ 1. Seal Leaks and Add Insulation

• Drafty windows and doors = wasted heat

• Check attic and basement insulation

✅ 2. Install a Programmable or Smart Thermostat

• Drop temp 6–8°F while sleeping or away

• Save up to 10% annually

External Link: Learn how smart thermostats save money from Consumer Reports

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✅ 3. Maintain Your Furnace

• Replace air filters every 1–3 months

• Get annual tune-ups to maintain efficiency

• Check for blocked vents or dirty burners

✅ 4. Upgrade Your Blower Motor

• ECM motors (standard in the GR9T801205DN) save energy and run quieter

• Improve comfort with more even airflow

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🛠️ When Is It Time to Consider an Upgrade?

If your current furnace is:

• Over 15 years old

• Frequently breaking down

• Producing inconsistent heat

• Using a pilot light instead of electronic ignition

…then even an 80% AFUE upgrade can lower your bills and improve comfort.

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✅ Pros of 80% AFUE Furnaces

✔️ Lower upfront cost
✔️ Easier installation (especially in homes with metal flues)
✔️ Reliable, proven technology
✔️ Ideal for warmer climates or seasonal use
✔️ Still meets federal minimum standards in most states

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❌ Limitations to Be Aware Of

❗ Wastes ~20% of fuel during combustion
❗ Not eligible for all energy rebates
❗ Venting may need chimney liner or special adjustments
❗ Less efficient in very cold climates (consider 90+ AFUE)

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🧭 Is the GR9T801205DN Right for You?

The Goodman GR9T801205DN is a strong choice if:

• You live in a moderate or warm climate

• You want quiet, two-stage performance

• You have an existing chimney flue

• You want to save $1,000+ upfront vs. high-efficiency

Its 80% AFUE and 120,000 BTU capacity offer plenty of heat for larger homes, and its multi-speed blower motor enhances comfort and energy control.

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📝 Samantha’s Final Word

Furnace efficiency matters—but it’s just one part of the equation.

If you’re trying to decide whether an 80% AFUE furnace is worth it, ask yourself:

• How many months of the year do I run my heat?

• Is my gas bill out of control—or manageable?

• Am I planning to stay in this home long-term?

If you live in a southern or moderate zone, or your budget favors simplicity over ultra-efficiency, then a well-installed 80% AFUE model like the GR9T801205DN can absolutely meet your needs—without burning a hole in your wallet.

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📞 Need Help?

Still unsure how much a furnace will cost you to run? Send me your ZIP code, square footage, and gas rates, and I’ll calculate your expected winter bill and suggest the best model for your home.

— Samantha Reyes, Home Comfort Advisor

In the next topic we will read about: Maintenance Checklist for Goodman Gas Furnaces: Keep Your System Running Strong - By Samantha Reyes, Home Comfort Advisor