A.O. Smith vs Navien: Full-Line Tank Brand vs Condensing Tankless Specialist
A.O. Smith publishes tank, tankless, and hybrid heat pump electric water heaters in one catalog. Navien's published US residential lineup is centered on condensing tankless and combination boiler-water heater units. The two brands rarely compete on the exact same product.
Updated August 2026
Who wins what
Homeowners still deciding between tank, tankless, and heat pump formats.
Basis: A.O. Smith publishes tank, tankless, and hybrid heat pump electric lines; Navien's published US lineup centers on condensing tankless and combination units.
Homeowners who want one unit to supply both domestic hot water and hydronic space heating.
Basis: Navien publishes combination boiler-water heater models designed to serve both functions; A.O. Smith's published residential catalog does not include a combination unit in the same category.
Everyone, since neither publishes installed pricing.
Basis: Neither manufacturer publishes a combined equipment-plus-labor installed price.
Key differences at a glance
Core product focus
A.O. Smith- A.O. Smith
- Full catalog: tank, tankless, and hybrid heat pump electric water heaters
- Navien
- Condensing tankless water heaters and combination boiler-water heater units
Tankless heat exchanger warranty
Navien- A.O. Smith
- Published 12-year heat exchanger, 5-year parts on residential condensing tankless models
- Navien
- Published 15-year heat exchanger warranty on residential condensing tankless models, with parts terms varying by model
Fuel type coverage
A.O. Smith- A.O. Smith
- Gas, electric, and heat pump electric
- Navien
- Gas only across its published tankless and combination lineup
Combination space and water heating
Navien- A.O. Smith
- Not published in A.O. Smith's mainstream residential catalog
- Navien
- Published combination boiler-water heater models available
Full scorecard
| Metric | A.O. Smith | Navien | Edge |
|---|---|---|---|
| Tank warrantyRow excluded from direct comparison since Navien does not publish a standard tank line | 6 to 12 years by tier, registered | Not applicable; Navien's mainstream published lineup is tankless and combination units | Even |
| Parts warrantyManufacturer limited warranty documentation | 5 years on A.O. Smith's residential tankless models | Varies by model; published documentation lists differing parts terms across Navien's tankless and combination lines | Even |
| First-hour rating or flow rateManufacturer spec sheets | Tank models publish first-hour rating (GPH); tankless models publish flow rate (GPM) by model | Flow rate (GPM) published by model and groundwater temperature | Even |
| Fuel typeManufacturer product catalogs | Gas, electric, and heat pump electric | Gas only | A.O. Smith |
Which one is right for you?
Choose A.O. Smith if…
- You want to compare tank, tankless, and heat pump electric options from A.O. Smith's catalog before committing to Navien's condensing-tankless-only lineup.
- You need an electric or heat pump water heater, which Navien does not publish in its mainstream US catalog.
- You want a standard tank replacement rather than a condensing tankless system.
Choose Navien if…
- You want a combination unit that supplies both domestic hot water and hydronic space heating from one appliance.
- You have already decided on condensing tankless and your contractor is Navien-certified.
- Your published warranty comparison for the specific models quoted favors Navien's heat exchanger term.
Choose neither if…
- Your gas line, venting, or electrical service has not been assessed by a licensed contractor for a tankless or combination unit.
- Your current tank is still under its A.O. Smith or other manufacturer warranty and the failure is a thermostat, element, or anode rod rather than the tank itself.
- You have not compared written quotes for A.O. Smith and Navien from the same local installer before assuming either brand's price.
The short answer
A.O. Smith publishes tank, tankless, and heat pump water heaters in one catalog. Navien's published lineup centers on condensing tankless and combination boiler-water heater units, with a longer published heat exchanger warranty on some models. Neither company publishes installed pricing or independent reliability data.
Cost breakdown
| Line item | A.O. Smith | Navien |
|---|---|---|
| Condensing tankless unit, mid-capacity residential | Listed at some retailers; wholesale pricing also common | Not published by the manufacturer |
| Combination boiler-water heater unit | Not published in A.O. Smith's mainstream catalog | Not published by the manufacturer |
| Installation labor | Set by the installer | Set by the installer, often higher for combination units due to added hydronic piping |
| Permits | Set by your jurisdiction | Set by your jurisdiction |
Combination units that also serve space heating typically involve more piping and controls work than a standalone water heater, which a licensed contractor should itemize separately from the water heating portion of the job.
Decision framework
A.O. Smith publishes all three formats; Navien's mainstream catalog is tankless and combination units.
Navien publishes combination boiler-water heater models designed for that dual role.
Navien's published US residential lineup does not include a standard electric tank line.
For A.O. Smith versus Navien, parts access and combi-unit service experience depend on the installer your contractor represents.
- Assuming Navien sells a mainstream electric or heat pump water heater; its published US lineup centers on gas tankless and combination units.
- Comparing a combination unit's installed cost to a standalone tankless unit without separating the hydronic piping work.
- Assuming every Navien model carries the same heat exchanger warranty term; published terms vary by model line.
- You are assuming A.O. Smith's tankless dimensions or Navien's combi unit will fit your existing tank closet without a contractor confirming gas line and venting changes first.
- Not confirming that a licensed plumber or HVAC contractor, not a general handyman, performs any gas line, venting, or hydronic piping work.
Tools and next steps
Frequently compared next
Frequently asked questions
Does A.O. Smith make condensing tankless water heaters?
Yes. A.O. Smith publishes residential condensing gas tankless models alongside its tank and hybrid heat pump electric lines.
Does Navien make tank water heaters?
Navien's mainstream published US residential lineup is condensing tankless and combination boiler-water heater units. It does not publish a standard tank-only line comparable to A.O. Smith's tank catalog.
What is a combination unit and does A.O. Smith make one?
A combination unit supplies both domestic hot water and hydronic space heating from a single appliance. Navien publishes combination models in this category; A.O. Smith's mainstream residential catalog does not include a directly comparable product.
Which brand has the longer tankless heat exchanger warranty?
Navien publishes a 15-year heat exchanger warranty on some residential condensing tankless models, compared with a published 12-year term on A.O. Smith's residential condensing tankless line. Confirm the exact tier for the model quoted.
Is one brand more reliable than the other?
We found no independent public dataset ranking A.O. Smith against Navien for reliability or repair frequency, so we do not publish a ranking.
Is gas line, venting, or hydronic piping work involved in either installation safe to do myself?
No, for an A.O. Smith tankless unit or a Navien tankless or combi unit. Gas line, venting, and combustion-related work should be evaluated and performed by a licensed plumbing or HVAC contractor in accordance with local plumbing and mechanical codes. Do not attempt gas line, flue, or venting modifications yourself.
Verify these details yourself
- Installed price for either brand in your local market.
- Whether your local contractor stocks both brands or only one.
- Real-world reliability or failure rates; no independent dataset was found.
- Exact warranty terms for the specific model line quoted, which vary within each brand's catalog.
- Whether a combination unit is appropriate for your home's existing hydronic distribution, if any.
Methodology and sources
Specifications, pricing, warranties, and availability may change. We verify key details against official or reputable public sources and note where information is estimated or not publicly disclosed. HomeownerAnswers does not perform product testing.
- A.O. Smith water heater warranty documentation - Official manufacturer, checked 2026-08-03, confidence: high
- Navien tankless and combination unit warranty documentation - Official manufacturer, checked 2026-08-03, confidence: high
- ENERGY STAR water heater criteria - Government, checked 2026-08-03, confidence: high
- Department of Energy water heater efficiency guidance - Government, checked 2026-08-03, confidence: high
Search another homeowner question
Costs, repair vs replace, financing, insurance - get an answer in seconds.
Estimates and guidance are educational. Always confirm with a licensed local professional before making decisions.