Noritz NR66-OD
Amazon customer rating as of
Tankless Geek editorial score: 4.2/5
The Noritz NR66-OD is a compact outdoor non-condensing gas tankless: 140,000 BTU/h, up to 6.6 GPM, and about 0.83 EF, in a weatherproof cabinet built for exterior mounting. Because it installs outdoors, it needs no indoor venting or condensate drain — a real simplification for warm-climate homes, cabins, and small houses where freezing is rare. It uses direct electronic ignition (no standing pilot), operates from 115–140 °F, and includes a full safety package: flame sensor, overheat prevention, and even lightning protection. Noritz backs it with a strong 12-year heat-exchanger warranty.
As a non-condensing outdoor unit it's simpler and cheaper to install than a condensing indoor heater, but it's less efficient and, like all tankless, its flow tracks inlet temperature: about 6.6 GPM at a warm rise, dropping toward 3.3 GPM in colder water. It's best where winters are mild — outdoor units risk freezing in hard cold without protection. With a ~4.2-star rating, owners value the easy outdoor install, reliability, and Noritz build quality. For a small warm-climate home or cabin, it's a clean, low-hassle way to endless hot water.
Key Features
Best Use Cases
Our Verdict
A well-built outdoor non-condensing tankless that skips indoor venting entirely — ideal for a small warm-climate home or cabin. Simple install, reliable Noritz engineering, and a 12-year heat-exchanger warranty. Just keep it to mild-winter regions and size expectations to its 6.6 GPM.
Technical Specifications
| Input | Up to 140,000 BTU/h (natural gas) |
|---|---|
| Max flow | Up to 6.6 GPM |
| Efficiency | ≈0.83 EF, non-condensing |
| Install | Outdoor, weatherproof — no indoor venting/condensate |
| Ignition | Direct electronic; 115–140 °F |
| Safety & warranty | Flame/overheat/lightning protection; 12-yr HX |
Specifications verified against the linked source documents. See Sources below.
How much hot water you'll actually get
Usable flow drops as incoming water gets colder. Figures are calculated from rated output (140,000 BTU × 0.83 UEF) and labeled as such — not bench-tested by us.
| Temperature rise | Typical scenario | Usable flow |
|---|---|---|
| 35 °F | Warm climate (75 °F in → 110 °F) — capped at max | 6.6 GPM |
| 45 °F | Mild climate (65 °F in → 110 °F) | 5.2 GPM |
| 60 °F | Cool climate (50 °F in → 110 °F) | 3.9 GPM |
| 70 °F | Cold climate (40 °F in → 110 °F) | 3.3 GPM |
Usable flow at a 110 °F target: BTU × thermal-eff ÷ (ΔF × 500), capped at the 6.6 GPM maximum (non-condensing ~83%). Minimum output setting is 115 °F.
Pros
Cons
Buy it if…
- Small warm-climate homes and cabins
- Installs that benefit from no indoor venting or condensate drain
- Buyers wanting Noritz build quality on a simpler unit
- Exterior-mount replacements for a small tank
Skip it if…
- Cold-climate regions with hard freezes (outdoor freeze risk)
- Large homes needing high simultaneous flow
- Efficiency-focused buyers (this is non-condensing)
Installation Requirements
Professional vs DIY
Outdoor mounting removes the venting complexity, but the gas connection should still be done by a licensed pro.
Gas and electrical work should be done by a licensed professional, and most installs require a permit and must meet local building codes — DIY work can void the manufacturer warranty. Always confirm the unit's own manual for exact clearances, venting, and sizing.
What owners report
Themes summarized from retailer customer feedback (4.2/5 Amazon customer rating, 35 ratings, as of 2026-09-06). These are owner opinions, not our own bench testing.
Owners value that outdoor mounting eliminates indoor venting and condensate work, simplifying the whole job.
Reviewers credit dependable operation and quality engineering, with lightning and overheat protection built in.
At 6.6 GPM it suits small homes and cabins; owners note it isn't meant for heavy simultaneous demand.
As an outdoor unit it's best in mild-winter regions; hard freezes require added freeze protection.
Noritz NR66-OD FAQ
Does the NR66-OD need venting?+
No — it mounts outdoors, so it needs no indoor venting or condensate drain. That's its main install advantage in warm climates.
Can I use it in a cold climate?+
It's best in mild-winter regions. As an outdoor unit it can be at risk of freezing in hard cold without additional freeze protection.
How many fixtures can it run?+
Up to about 6.6 GPM in warm climates — a couple of fixtures — dropping toward 3.3 GPM as inlet water gets colder.
Does it have a standing pilot?+
No — it uses direct electronic ignition, so there's no constantly-burning pilot flame to waste gas.
What flow can the NR66-OD deliver at a high temperature rise?+
Being outdoor-installed, the NR66-OD skips indoor venting entirely, but its output still sets the limit. Estimated from its 140,000 BTU/h natural-gas input at about 0.83 efficiency, realistic usable flow is roughly 5.2 GPM at a 45 °F rise and about 3.3 GPM at a 70 °F winter rise, versus the 6.6 GPM warm-inlet rating. That's comfortable two-fixture capacity in most climates. Because it mounts outside, it's best suited to regions with mild-to-moderate winters; its freeze protection needs power to run.
Product sources
Specifications verified 2026-09-06. Manufacturer documents are treated as the primary source for model specifications. Retailer pages are used only for customer ratings and owner-feedback themes.
- Noritz NR66-OD-NG — PlumbersStock specs (accessed 2026-09-06)
- NR66-OD-NG — Noritz support & specs (accessed 2026-09-06)
- NR66-OD-NG specification sheet (PDF) (accessed 2026-09-06)
Price range from leading retailers
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