Description
Efficiency Performance
At 99% AFUE, the Lennox SLP99V converts virtually all of its fuel energy into usable heat — only 1% is lost through exhaust. This is the highest efficiency rating available in Lennox’s furnace lineup and represents the maximum fuel savings a gas furnace can deliver.
Burner Technology
The SLP99V features a modulating gas burner that adjusts its output in small increments rather than simply cycling on and off. This allows the furnace to match its heating output precisely to your home’s demand at any given moment, virtually eliminating the temperature swings associated with simpler systems. Lennox indicates that, the burner can operate as low as 40% of its maximum capacity during milder conditions.
Blower System
Paired with the modulating burner, the SLP99V’s variable-speed ECM blower adjusts airflow to match the burner’s current output level. This coordination means air moves through your home at the ideal speed for the heating demand at any moment, reducing drafty sensations and keeping temperatures remarkably consistent from room to room. Lennox states that, the ECM motor uses significantly less electricity than conventional blower motors.
Warranty Protection
The Signature Series SLP99V comes with a lifetime heat exchanger warranty — one of the strongest in the industry. Lennox requires product registration within 60 days of installation to activate the extended warranty coverage; without registration, coverage defaults to the base 10 years parts warranty.
- Base Parts Warranty: 10 years
- Base Heat Exchanger Warranty: Lifetime
- Extended Parts Warranty: 12 years (with registration)
- Extended Heat Exchanger Warranty: Lifetime (with registration)
- Registration Period: 60 days from installation
- Labour Warranty: Not included — varies by installer
- Unit Replacement: Not available
What Homeowners Are Saying
Among homeowners who’ve shared their feedback with us, Lennox’s premium modulating furnace equipment consistently draws praise for precision heating and whisper-quiet operation. Owners who’ve upgraded to the SLP99V repeatedly describe the step up in comfort refinement as immediately noticeable the first time the unit fires up.
Quiet operation is the most frequently cited positive in the feedback we’ve collected, with owners noting a clear difference compared to older equipment. Energy efficiency comes up almost as often — several SLP99V owners report meaningful reductions in their gas bills once a full heating season is behind them. As one SLP99V owner put it: “Very efficient and quiet.”
One area that occasionally draws criticism is Lennox’s warranty registration process — owners stress the importance of confirming your installer completes registration within the 60-day window, as missing that deadline reduces coverage. As with any premium equipment, proper installation by a qualified contractor is essential to realize the full performance the SLP99V offers.
Our Verdict
The Lennox SLP99V is a premium investment in home comfort. With 99% AFUE efficiency, modulating burner technology, and Lennox’s Signature-level lifetime heat exchanger warranty, it delivers the most refined heating experience in the Lennox lineup. The higher upfront cost is offset by lower operating costs and a level of comfort precision that lower-tier models simply can’t match.
This furnace is best suited for:
- Homeowners who prioritize maximum comfort and minimal temperature variation
- Those looking for the highest possible gas furnace efficiency to minimize fuel costs
- Buyers who value premium warranty coverage, including a lifetime heat exchanger warranty
- Homes in cold climates where the furnace runs frequently and efficiency gains compound over time
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