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The Lennox SLP99V isn’t just a high-efficiency furnace — it’s one of the most advanced residential heating systems available today.
Designed as the flagship model in Lennox’s Signature Collection, it uses fully modulating technology to deliver heat in small, continuous adjustments rather than the typical on/off cycling. The result is exceptionally stable indoor temperatures, quieter performance, and improved energy efficiency.
This is a furnace built for homeowners who want maximum comfort, minimal noise, and top-tier performance, not just basic heating.
What We Love
Best-in-Class Efficiency: With up to 99% AFUE, the SLP99V sits at the top of the efficiency scale, making it an excellent choice for cold climates and high heating demand.
Precision Temperature Control: The modulating gas valve adjusts output in tiny increments, eliminating the noticeable temperature swings common with single- and two-stage furnaces.
Ultra-Quiet Operation: Thanks to SilentComfort® technology and an insulated cabinet, this is one of the quietest furnaces on the market — ideal for noise-sensitive homes.
Advanced Smart Integration: Pairs seamlessly with Lennox iComfort® thermostats and indoor air quality systems, enabling full system control and automation.
What to Consider
Premium Price Point: This is one of the most expensive furnaces available, and the upfront cost may not make sense for every homeowner.
Diminishing Efficiency Returns: While 99% AFUE is impressive, the real-world savings compared to a 96 to 98% furnace are relatively small.
System Compatibility Requirements: To get the most out of this furnace, you’ll likely need Lennox-compatible components and a certified installer.
Lennox SLP99V Furnace Specifications
Lennox SLP99V Furnace Specifications
Feature
Specification
AFUE
Up to 99%
Gas Valve
Fully modulating
Blower Motor
Variable-speed ECM
Noise Reduction
SilentComfort® technology, insulated cabinet
Smart Controls
iComfort® thermostat, zoning, IAQ compatibility
Warranty
Lifetime heat exchanger, 10-year parts (with registration)
Costs vary by region, but premium furnaces like the SLP99V typically fall within these ranges:
Lennox SLP99V Cost + Savings
Region
Estimated Installed Cost (SLP99V)
Avg Annual Heating Fuel Cost*
Estimated Annual Savings vs. Mid-Efficiency (90 to 94% AFUE)
South
$8,500 to $11,500
~$1,100 to $1,400
$150 to $250
Midwest
$9,000 to $12,500
~$1,300 to $1,700
$200 to $350
Northeast
$10,000 to $13,500+
~$1,500 to $2,000
$250 to $400
West
$9,500 to $13,000
~$1,400 to $1,800
$200 to $350
*Based on natural gas fuel costs, a 2,000-sq ft home in a typical climate, and moderate heating usage. Actual costs vary with local utility rates and home insulation.
The SLP99V is ENERGY STAR® Most Efficient certified, which may qualify you for:
Upgrading from a 90 to 94% AFUE furnace to the SLP99V can result in:
$150 to $400+ in annual savings, depending on your climate and usage
However, compared to a modern 96 to 98% furnace, savings are typically modest. The real advantage comes from:
Improved comfort
More consistent airflow
Reduced noise
Maintenance & Longevity
Expected lifespan: 15 to 20+ years
To keep it running efficiently:
Schedule annual professional maintenance
Replace filters every 1 to 3 months
Keep vents and airflow pathways clear
Maintain thermostat calibration
Because it runs in smaller, continuous adjustments, it often experiences less wear and tear than traditional systems.
Lennox SLP99V Furnace Customer Feedback
What homeowners like:
Nearly silent operation
Even, consistent heating
Noticeable comfort improvement
Common concerns:
Higher upfront cost
Limited installer availability in some areas
Higher repair costs outside warranty
Final Thoughts: Is the Lennox SLP99V Worth It?
The Lennox SLP99V is one of the most advanced furnaces available, offering exceptional efficiency, precision comfort, and near-silent performance.
It’s not the most budget-friendly option, but for homeowners who want top-tier comfort and technology, it delivers on its promise.
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The Lennox SLP99V has an AFUE rating of up to 99%, making it one of the most efficient residential gas furnaces available. It converts nearly all fuel into usable heat, though real-world savings depend on your climate and current system.
How much does the Lennox SLP99V cost to install?
Most homeowners can expect to pay between $8,500 and $13,500+ installed. Final cost varies based on home size, installation complexity, ductwork condition, and local labor rates. Premium features and system upgrades can increase the total price.
Is the Lennox SLP99V quieter than other furnaces?
Yes. The SLP99V is widely considered one of the quietest furnaces on the market thanks to its modulating operation, variable-speed blower, and insulated cabinet. In many homes, it’s barely noticeable when running.
How long does a Lennox SLP99V furnace last?
With proper maintenance, the Lennox SLP99V furnace typically lasts 15 to 20 years or longer. Its variable operation can reduce wear compared to single-stage systems.
What warranty does Lennox offer on the SLP99V?
Lennox provides a lifetime limited warranty on the heat exchanger and a 10-year limited parts warranty with product registration. Coverage details may vary, so it’s important to confirm terms with your installer.
Is a 99% AFUE furnace worth it?
A 99% AFUE furnace is worth it if you want maximum efficiency, consistent comfort, and quiet performance. However, the energy savings over a 96% to 98% furnace are usually modest, so value depends on your priorities.
Is the Lennox SLP99V worth the cost?
The SLP99V is worth it for homeowners who prioritize maximum comfort, ultra-quiet performance, and top-tier technology. However, if your main goal is return on investment, a 96–98% efficiency furnace may offer similar savings at a lower upfront cost.
