Does gas tankless heater category determine width?
Widths differ within one category. Navien NHW-199SU is 14 in wide for indoor/outdoor installation; Rinnai RX199iN is 18.5 in wide in that category.
A qualified installer must establish demand, gas supply, venting and accessory needs.
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With no preferences selected: NHW-199AI Gas Tankless Water Heater is one option to compare.
Your choices are compared with each model’s product details. A missing or conflicting value stays unknown and cannot satisfy a choice you select. The starting order helps you browse; it does not rate real-world performance.
Source dates appear with each link below. A source date does not confirm today's price or stock.
EZTR75 Tankless Water Heater Bundle: Source 1 ↗ · September 28, 2026
NHW-199AI Gas Tankless Water Heater: Source 1 ↗ · September 28, 2026
NHW-199SU Gas Tankless Water Heater: Source 1 ↗ · September 28, 2026
NPE-240A2 Gas Tankless Water Heater: Source 1 ↗ · September 28, 2026
NPE-240S2 Gas Tankless Water Heater: Source 1 ↗ · September 28, 2026
RE199iN Gas Tankless Water Heater: Source 1 ↗ · September 28, 2026
REP199iN Gas Tankless Water Heater: Source 1 ↗ · September 28, 2026
RX199iN Gas Tankless Water Heater: Source 1 ↗ · September 28, 2026
RXP199iN Gas Tankless Water Heater: Source 1 ↗ · September 28, 2026
V75iN Gas Tankless Water Heater: Source 1 ↗ · September 28, 2026
Efficiency and cabinet width can pull in different directions
Maker UEF ratings range from 0.81 to 0.98, while cabinet widths run from 14 to 18.5 in. Rinnai's 0.98 UEF models are 18.5 in wide; Navien has a 0.81 UEF model at 14 in. If your available space is narrow, do not assume the higher efficiency figure comes in the same cabinet width.
UEF describes efficiency, not the hot-water output your household needs or an operating-cost estimate. Cabinet width excludes the service and installation clearances that the manual calls for. Household capacity stays unresolved by the specifications; delivered hot water has not been measured here.
A location label cannot settle the gas and venting plan
Rinnai and Navien each have indoor-only and indoor-or-outdoor selections in this group. Noritz's selection is a bundle, not simply a bare heater. Compare what is supplied and the exact location designation; a dual-location label can still come with outdoor accessory conditions.
Bring the model's performance data to a qualified installer to resolve capacity, gas-supply compatibility, venting and clearances. The page's efficiency, width and location fields cannot make those decisions.
Manufacturer pages can direct you to installers or distributors instead of offering immediate checkout.
Before you buy
Does the page size a heater for my household?
It does not calculate simultaneous demand, incoming-water temperature or temperature rise. Before you order, the installer needs the exact performance data for those conditions. Navien NHW-199SU is 14 in wide for indoor or outdoor installation; Rinnai RX199iN is 18.5 in wide in the same category. Installation category does not determine width. NHW-199SU suits you if cabinet width is tight. RX199iN needs more room. A qualified installer must establish demand, gas supply, venting and accessory needs.
Does outdoor use mean no extra parts?
A listed indoor-or-outdoor scope can still require a vent cap or other accessories. The category is not installation approval; read the exact manual.
Will a higher UEF establish a lower bill?
Navien NPE-240S2 gives 0.96 UEF and NPE-240A2 gives 0.95 UEF. These are manufacturer-page efficiency figures, without a bill estimate or hot-water-capacity calculation.
Can I buy directly from every page?
Some exact US manufacturer pages route purchases through installers or distributors. Local stock and installation pricing are not verified.
What is in Noritz EZTR75?
Its bundle includes an EZ111 heater, isolation valves and a flex vent kit. Treat it as a package rather than a bare heater when comparing included parts.
