A.O. Smith vs Rinnai: Full-Line Tank Brand vs Tankless Specialist
A.O. Smith publishes tank, tankless, and hybrid heat pump electric water heaters across a broad retail and contractor catalog, while Rinnai's published US residential lineup is built almost entirely around gas tankless units. The two only compete directly once you have already picked a format.
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 in one catalog; Rinnai's mainstream US residential lineup is gas tankless plus a hybrid tank-tankless model.
Homeowners who have already decided on gas tankless.
Basis: Rinnai publishes a longer continuous US tankless product history than A.O. Smith's tankless entry into the 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
- Rinnai
- Primarily gas tankless, with a hybrid tank-tankless product
Tankless heat exchanger warranty
Even- A.O. Smith
- Published 12-year heat exchanger, 5-year parts on A.O. Smith's residential condensing tankless line
- Rinnai
- Published 12-year heat exchanger, 5-year parts, 1-year labor on Rinnai's residential tankless line
Fuel type coverage
A.O. Smith- A.O. Smith
- Gas, electric, and heat pump electric
- Rinnai
- Gas only across its published tankless lineup
Distribution
Even- A.O. Smith
- Retail, online, wholesale, and contractor
- Rinnai
- Wholesale, contractor, and growing retail presence
Full scorecard
| Metric | A.O. Smith | Rinnai | Edge |
|---|---|---|---|
| Tank warrantyRow excluded from direct comparison since Rinnai does not publish a standard tank line | 6 to 12 years by tier, registered | Not applicable; Rinnai's mainstream published lineup is tankless | Even |
| Parts warrantyManufacturer limited warranty documentation | 5 years on A.O. Smith's residential tankless models | 5 years on Rinnai's residential tankless models | 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 A.O. Smith's published condensing tankless line plus the option of a tank or hybrid heat pump electric unit from the same catalog.
- You need an electric or heat pump model, a format A.O. Smith publishes but Rinnai's mainstream US catalog does not.
- You want retail price visibility at a big-box retailer before contacting a contractor.
Choose Rinnai if…
- You have already committed to gas tankless and want the brand with the longest continuously published US tankless track record.
- Your contractor is a certified Rinnai installer with established parts access in your area.
- You want a tankless-focused manufacturer rather than a diversified tank-and-tankless catalog.
Choose neither if…
- Your gas line, venting, or electrical service has not been assessed by a licensed contractor for a tankless conversion.
- Your current tank is under warranty and the failure is a low-cost part rather than the tank itself.
- You have not yet obtained a written quote confirming which brand your local installer actually stocks and services.
The short answer
A.O. Smith publishes tank, tankless, and heat pump water heaters in one catalog. Rinnai is a tankless specialist with a longer published US tankless track record and a narrower published lineup. On comparable gas tankless models, published warranty terms are close. Neither company publishes installed pricing or independent reliability data.
Cost breakdown
| Line item | A.O. Smith | Rinnai |
|---|---|---|
| Tankless unit, mid-capacity residential | Listed at some retailers; wholesale pricing also common | Not published by the manufacturer |
| Venting and gas line modification | Set by the contractor; often required for tankless conversions | Set by the contractor; often required for tankless conversions |
| Installation labor | Set by the installer | Set by the installer |
| Permits | Set by your jurisdiction | Set by your jurisdiction |
Neither brand publishes an installed price that bundles equipment and labor. Tankless conversions from a tank frequently require gas line upsizing or new venting, which a licensed contractor must price separately from the unit itself.
Decision framework
A.O. Smith publishes all three formats; Rinnai's mainstream catalog is tankless.
Rinnai's published US residential lineup does not include a standard electric tank line.
Rinnai publishes a longer continuous US tankless product history.
Parts availability and warranty service depend on the installer's supplier relationship.
- Assuming Rinnai sells a mainstream electric or heat pump water heater; its published US lineup centers on gas tankless.
- Comparing A.O. Smith's entry-tier tankless warranty against Rinnai's mid-tier model and calling the gap a brand-wide difference.
- Skipping a gas line and venting assessment before assuming either brand's tankless unit will drop into an existing tank's space.
- Assuming a retail-listed A.O. Smith tankless price includes venting, gas line work, and disposal of the old tank.
- Not confirming that a licensed plumber, not a general handyman, performs any gas line or venting work involved in a tankless conversion.
Tools and next steps
Frequently compared next
Frequently asked questions
Does A.O. Smith make gas tankless water heaters?
Yes. A.O. Smith publishes residential gas tankless models, including condensing units, alongside its tank and hybrid heat pump electric lines.
Does Rinnai make tank water heaters?
Rinnai's mainstream published US residential lineup is gas tankless plus a hybrid tank-tankless product. It does not publish a standard tank-only line comparable to A.O. Smith's tank catalog.
Which brand has the longer tankless warranty?
Published tankless warranty terms are similar on comparable residential models from both brands, commonly a 12-year heat exchanger and 5-year parts tier. Confirm the exact tier for the specific model quoted.
Is one brand more reliable than the other?
We found no independent public dataset ranking A.O. Smith against Rinnai for reliability or repair frequency, so we do not publish a ranking.
Can I replace an existing tank with either brand's tankless unit without other changes?
Not always. Tankless units often require larger gas lines, new venting, or an electrical circuit for the internal controls; a licensed contractor needs to assess your home before quoting either brand.
Is gas line or venting work involved in either installation safe to do myself?
No. A.O. Smith's and Rinnai's published installation manuals both call for a licensed plumbing or gas contractor to size the gas line, set the venting, and inspect the combustion air path. Do not attempt that work 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 your existing gas line and venting can support a tankless conversion without upsizing.
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
- Rinnai residential tankless 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
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Estimates and guidance are educational. Always confirm with a licensed local professional before making decisions.