A.O. Smith Signature 6.6 GPM
The A.O. Smith Signature 6.6 GPM is the retail-channel condensing tankless — the Signature Premier indoor natural-gas unit sold through Lowe's — rated at 160,000 BTU/h, up to 6.6 GPM, roughly 0.94 UEF, and ENERGY STAR certified. It's aimed squarely at the mainstream homeowner replacing a tank: condensing efficiency, lighter PVC venting, and a long 15-year heat-exchanger warranty, at a price below the pro-channel ProLine models.
Six-and-a-half GPM is a solid two-bathroom capacity in warm and mild climates, tapering to a comfortable single-shower-plus in the cold. Owners consistently praise quiet operation and steady temperatures. The recurring caution — common to A.O. Smith's tankless line — is service: a minority report early failures and slow or hard-to-reach warranty support in some regions. For a typical home wanting condensing efficiency from a familiar brand at a retail price, it's a sensible pick; just line up a qualified installer and register promptly.
Key Features
Best Use Cases
Our Verdict
A well-priced condensing tankless for mainstream two-bath homes, with real efficiency and a long heat-exchanger warranty from a familiar brand. Quiet and steady in daily use. The asterisk is warranty service, which owners rate unevenly — register on time and know your local authorized-service situation before buying.
What owners report
Themes summarized from verified-purchase reviews across major retailers (4.2★ average, 34 ratings). These are aggregated owner opinions — not our own bench testing.
The most consistent praise: near-silent operation and stable water temperature during use.
Owners upgrading from a tank cite lower gas bills and endless hot water for a two-bath home.
A minority report failures within months and slow warranty support — some note authorized plumbers hard to find locally.
As with the brand generally, timely registration and professional installation matter for honoring the 15-year exchanger warranty.
A.O. Smith Signature 6.6 GPM FAQ
Is this a condensing unit?+
Yes — the Signature Premier indoor 6.6 GPM is condensing at roughly 0.94 UEF and ENERGY STAR certified, using lighter PVC venting and a condensate drain.
How many fixtures can it run?+
About two bathrooms' worth (6.6 GPM) in warm and mild climates. In deep cold it settles to a strong single-shower-plus-sink as deliverable flow drops.
How does it compare to the A.O. Smith ATI-540H?+
The ATI-540H is a bigger, pro-channel 199,000 BTU / 10 GPM heater for heavy use and recirculation. The Signature 6.6 GPM is the retail two-bath unit at a lower price.
What's the warranty?+
15 years on the heat exchanger and 5 years on parts for residential use. Register promptly and use a qualified installer to keep coverage valid.
Price range from leading retailers
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