10 models to compare

Tankless water heaters: which size and energy source?

Cabinet size does not determine suitability. Navien NPN-199U is gas at 14 x 23 in; EcoSmart ECO 11 is electric at 7.9 x 11.4 in.

Allow pipes, venting and service access. A qualified installer must assess application and demand.

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With no preferences selected: ECO 11 Tankless Water Heater is one option to compare.

No hands-on testingMethod and sources

ECO 11 Tankless Water Heater · first with a product link

Energy source: Electric.
Cabinet width: 7.9 in.

What to note:

Cabinet height: 11.4 in.

View at EcoSmart

If you choose Gas for energy source, the first option with a product link becomes NHW-199AE Tankless Water Heater.

10 models compared; 10 have a product-page link.

The picks

5 options to compare

Compare the details that matter to your setup.

An option to compare

ECO 11 Tankless Water Heater

Energy source: Electric.

Key details

Cabinet width: 7.9 in.

What to note

Cabinet height: 11.4 in.

Compare specs: Energy source: Electric here; Gas on NHW-199AE Tankless Water Heater.

Energy source: ElectricCabinet width: 7.9 inCabinet height: 11.4 in

See all 3 specs

Energy sourceElectric

Cabinet width7.9 in

Cabinet height11.4 in

3 of 3 specs available · source checked September 29, 2026 · Source ↗
EcoSmart · Product page checked September 29, 2026

View at EcoSmart Compare

Energy source: Gas

NHW-199AE Tankless Water Heater

Cabinet height: 26 1/2 in.

Key details

Cabinet width: 17.3 in.

What to note

Energy source: Gas.

Compare specs: Cabinet height: 26 1/2 in here; 27.4 in on NPE-210A2 Tankless Water Heater.

Energy source: GasCabinet width: 17.3 inCabinet height: 26 1/2 in

See all 3 specs

Energy sourceGas

Cabinet width17.3 in

Cabinet height26 1/2 in

3 of 3 specs available · source checked September 29, 2026 · Source ↗
Navien · Product page checked September 29, 2026

View at Navien Compare

Also compare 3

NPE-210A2 Tankless Water Heater

Cabinet width: 17.3 in.

Key details

Cabinet height: 27.4 in.

What to note

Energy source: Gas.

Compare specs: Cabinet width: 17.3 in here; 14 in on NPN-199U Tankless Water Heater.

Energy source: GasCabinet width: 17.3 inCabinet height: 27.4 in

See all 3 specs

Energy sourceGas

Cabinet width17.3 in

Cabinet height27.4 in

3 of 3 specs available · source checked September 29, 2026 · Source ↗
www.supplystop.com · Product page checked September 30, 2026

View at www.supplystop.com Compare

Also compare 4

NPN-199U Tankless Water Heater

Cabinet width: 14 in.

Key details

Cabinet height: 23 in.

What to note

Energy source: Gas.

Compare specs: Cabinet width: 14 in here; 14.05 in on RE140iP Tankless Water Heater.

Energy source: GasCabinet width: 14 inCabinet height: 23 in

See all 3 specs

Energy sourceGas

Cabinet width14 in

Cabinet height23 in

3 of 3 specs available · source checked September 29, 2026 · Source ↗
Navien · Product page checked September 29, 2026

View at Navien Compare

Also compare 5

EZTR40 / NRC663-FSV Tankless Water Heater

Cabinet width: 18.3 in.

Key details

Cabinet height: 27.2 in.

What to note

Energy source: Gas.

Compare specs: Cabinet width: 18.3 in here; 17.3 in on NHW-199AE Tankless Water Heater.

Energy source: GasCabinet width: 18.3 inCabinet height: 27.2 in

See all 3 specs

Energy sourceGas

Cabinet width18.3 in

Cabinet height27.2 in

3 of 3 specs available · source checked September 29, 2026 · Source ↗
Noritz · Product page checked September 29, 2026

View at Noritz Compare

Comparing ECO 11 Tankless Water Heater · NHW-199AE Tankless Water Heater

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The facts that differ

Choose up to three models to compare side by side.

Differences only

0 identical specs shown. Details that do not apply to these models are omitted.

Published specification comparison
Spec	ECO 11 Tankless Water HeaterNo preferences selected.	NHW-199AE Tankless Water HeaterNo preferences selected.
Energy source	Electric	Gas
Cabinet width	7.9 in	17.3 in
Cabinet height	11.4 in	26 1/2 in

ECO 11 Tankless Water Heater

No preferences selected.

Energy source: Electric
Cabinet width: 7.9 in
Cabinet height: 11.4 in

NHW-199AE Tankless Water Heater

No preferences selected.

Energy source: Gas
Cabinet width: 17.3 in
Cabinet height: 26 1/2 in

ECO 11 Tankless Water Heater

View at EcoSmart

NHW-199AE Tankless Water Heater

View at Navien

Compare all 10 models

— = no verified listing yet. The published order is independent of links.

All models and their decision specs
Product	How it compares	Key spec	Compare	Action
ECO 11 Tankless Water Heater	Compared with NHW-199AE Tankless Water Heater: energy source, Electric vs Gas.	Energy source: Electric	Compare	View at EcoSmart
NHW-199AE Tankless Water Heater	Compared with NPE-210A2 Tankless Water Heater: cabinet height, 26 1/2 in vs 27.4 in.	Energy source: Gas	Compare	View at Navien
NPE-210A2 Tankless Water Heater	Compared with NPN-199U Tankless Water Heater: cabinet width, 17.3 in vs 14 in.	Energy source: Gas	Compare	View at www.supplystop.com
NPN-199U Tankless Water Heater	Compared with RE140iP Tankless Water Heater: cabinet width, 14 in vs 14.05 in.	Energy source: Gas	Compare	View at Navien
EZTR40 / NRC663-FSV Tankless Water Heater	Compared with NHW-199AE Tankless Water Heater: cabinet width, 18.3 in vs 17.3 in.	Energy source: Gas	Compare	View at Noritz
RE140iP Tankless Water Heater	Compared with RX199iN Tankless Water Heater: cabinet width, 14.05 in vs 18 1/2 in.	Energy source: Gas	Compare	View at Rinnai
REP199iN Tankless Water Heater	Compared with RX199iN Tankless Water Heater: cabinet width, 14.05 in vs 18 1/2 in.	Energy source: Gas	Compare	View at Rinnai
RX199iN Tankless Water Heater	Compared with Tempra 20 Plus Tankless Water Heater: energy source, Gas vs Electric.	Energy source: Gas	Compare	View at Rinnai
RXP199iN Tankless Water Heater	Compared with Tempra 20 Plus Tankless Water Heater: energy source, Gas vs Electric.	Energy source: Gas	Compare	View at Rinnai
Tempra 20 Plus Tankless Water Heater	Energy source: Electric.	Energy source: Electric	Compare	View at Stiebel Eltron

ECO 11 Tankless Water Heater

Compared with NHW-199AE Tankless Water Heater: energy source, Electric vs Gas.

Energy source: Electric

CompareView at EcoSmart

NHW-199AE Tankless Water Heater

Compared with NPE-210A2 Tankless Water Heater: cabinet height, 26 1/2 in vs 27.4 in.

Energy source: Gas

CompareView at Navien

NPE-210A2 Tankless Water Heater

Compared with NPN-199U Tankless Water Heater: cabinet width, 17.3 in vs 14 in.

Energy source: Gas

CompareView at www.supplystop.com

NPN-199U Tankless Water Heater

Compared with RE140iP Tankless Water Heater: cabinet width, 14 in vs 14.05 in.

Energy source: Gas

CompareView at Navien

EZTR40 / NRC663-FSV Tankless Water Heater

Compared with NHW-199AE Tankless Water Heater: cabinet width, 18.3 in vs 17.3 in.

Energy source: Gas

CompareView at Noritz

RE140iP Tankless Water Heater

Compared with RX199iN Tankless Water Heater: cabinet width, 14.05 in vs 18 1/2 in.

Energy source: Gas

CompareView at Rinnai

REP199iN Tankless Water Heater

Compared with RX199iN Tankless Water Heater: cabinet width, 14.05 in vs 18 1/2 in.

Energy source: Gas

CompareView at Rinnai

10 catalog models

How the comparison works

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.

Finder methodology Report a correction

Sources for all 10 models

ECO 11 Tankless Water Heater: Source 1 ↗ · September 29, 2026
EZTR40 / NRC663-FSV Tankless Water Heater: Source 1 ↗ · September 29, 2026
NHW-199AE Tankless Water Heater: Source 1 ↗ · September 29, 2026
NPE-210A2 Tankless Water Heater: Source 1 ↗ · September 29, 2026
NPN-199U Tankless Water Heater: Source 1 ↗ · September 29, 2026
RE140iP Tankless Water Heater: Source 1 ↗ · September 29, 2026
REP199iN Tankless Water Heater: Source 1 ↗ · September 29, 2026
RX199iN Tankless Water Heater: Source 1 ↗ · September 29, 2026
RXP199iN Tankless Water Heater: Source 1 ↗ · September 29, 2026
Tempra 20 Plus Tankless Water Heater: Source 1 ↗ · September 29, 2026

Start with the energy source and the installation

EcoSmart's electric cabinet measures 7.9 in wide by 11.4 in high. Rinnai's wider gas cabinet measures 18.5 in wide by 30.11 in high. That difference describes the cabinets, not how much hot water your household will receive.

The finder includes point-of-use equipment alongside larger units. Have a qualified installer check sizing guidance, the exact fuel variant and electrical supply before purchase. Our cabinet-spec comparison is not a household hot-water assessment.

The cabinet is smaller than the space an installation needs

Navien's shorter gas cabinet is 14 in wide by 23 in high, but pipes, venting, installation clearances and service access need additional room. Measure that whole installation space with the installer instead of treating a cabinet-size match as approval to install.

Stiebel Eltron's cabinet width and height are unknown here. Energy source remains usable, but an active dimension limit cannot confirm its fit. Consult the exact model's installation documentation; this finder does not resolve vent routes, circuit capacity or household supply capacity.

Before you buy

Does a cabinet fit establish installation?

Before you order, follow the exact installation manual for mounting, clearances, piping, venting and service access. Rinnai RX199iN’s cabinet dimensions do not include these allowances.

Are all gas or electric models interchangeable?

Fuel variants, conversion requirements and electrical supplies differ. Have a qualified installer confirm the exact model and supply before choosing equipment.

How should I compare household hot-water supply?

EcoSmart describes ECO 11 for one or two point-of-use applications. Required flow and incoming-water temperature need each maker’s sizing guidance; outside dimensions cannot answer that question.

Why is Tempra 20 Plus incomplete?

Its saved model page lacks the cabinet measurements. It cannot satisfy an active dimension preference while those values are unknown.

Does the Noritz offer include more than a heater?

EZTR40 is a bundle containing NRC663-FSV. Check the fuel version, included parts and dealer availability rather than assuming every model page describes the same package.