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Comparison
Verdict in brief
Both are condensing units in Navien's current S2 line in the same 17.3 in x 13.2 in cabinet, sharing UEF 0.96, the same 3/4 in gas and water connections, the same 0.5 GPM minimum flow and the same 2 in or 3 in PVC-family venting. The only real difference is the burner: the NPE-180S2 is 10,000–150,000 BTU/h and rates 8.4 GPM at a 35 °F rise and 4.3 GPM at a 67 °F rise, while the NPE-210S2 is 12,000–180,000 BTU/h and rates 10.1 GPM at 35 °F and 5.3 GPM at 67 °F. Metro Vancouver's winter rise to a 49 °C shower approaches 40 °C (72 °F), so the 67 °F row is the sizing number, and both are marginal for two simultaneous showers in January.
Published manufacturer figures with units. Storage and flow figures are different measures and are shown on their own rows; blanks mean not applicable or not published.
| Specification | Navien NPE-180S2Gas tankless | Navien NPE-210S2Gas tankless |
|---|---|---|
| Minimum gas input | 10,000 BTU/h | 12,000 BTU/h |
| Maximum gas input | 150,000 BTU/h | 180,000 BTU/h |
| Flow at a 35 °F (19.4 °C) rise | 8.4 GPM (31.8 L/min) at 35 °F (19.4 °C) rise | 10.1 GPM (38.2 L/min) at 35 °F (19.4 °C) rise |
| Flow at a 45 °F (25 °C) rise | 6.5 GPM (24.6 L/min) at 45 °F (25 °C) rise | 7.8 GPM (29.5 L/min) at 45 °F (25 °C) rise |
| Flow at a 67 °F (37.2 °C) rise | 4.3 GPM (16.3 L/min) at 67 °F (37.2 °C) rise | 5.3 GPM (20.1 L/min) at 67 °F (37.2 °C) rise |
| Minimum flow rate | 0.5 GPM (1.9 L/min) | 0.5 GPM (1.9 L/min) |
| Uniform Energy Factor (UEF) | 0.96 | 0.96 |
| Vent type | 2 in or 3 in PVC, CPVC, approved polypropylene or stainless steel; special gas vent type BH (Class II A/B/C) | 2 in or 3 in PVC, CPVC, approved polypropylene or stainless steel; special gas vent type BH (Class II A/B/C) |
| Gas connection | 3/4 in | 3/4 in |
| Water connections | 3/4 in cold inlet and hot outlet | 3/4 in cold inlet and hot outlet |
| Electrical supply | 120 V AC, 60 Hz | 120 V AC, 60 Hz |
| Height | 27.4 in (696 mm) | 27.4 in (696 mm) |
| Width | 17.3 in (439 mm) | 17.3 in (439 mm) |
| Depth | 13.2 in (335 mm) | 13.2 in (335 mm) |
| Weight | 68 lb (30.8 kg) | 73 lb (33.1 kg) |
| Maximum altitude | 10,100 ft for natural gas and propane | 10,100 ft for natural gas and propane |
“—” means not applicable to that system type or not published by the manufacturer. Flow figures are only comparable at the same temperature rise; UEF values are only comparable within the same draw pattern.
The S2 platform is where the two are identical. Both are rated UEF 0.96 on natural gas or propane, both take 2 in or 3 in PVC, CPVC, approved polypropylene or stainless venting (or BH special gas vent) as a forced-draft direct vent, both connect to 3/4 in gas and 3/4 in water, both have a 0.5 GPM (1.9 L/min) minimum flow, and both run on 120 V with a maximum altitude of 10,100 ft. Both support Navien's recirculation configuration with an external pump or crossover accessory.
What separates them is the heat input and the flow it produces. Navien publishes flow at three rises, which makes the comparison honest: at the 67 °F (37.2 °C) rise that matches a Metro Vancouver winter, the NPE-180S2 delivers 4.3 GPM (16.3 L/min) against the NPE-210S2's 5.3 GPM (20.1 L/min). A shower-class fixture draws about 7.5 to 9.5 L/min, so neither comfortably serves two showers at once in January, and the NPE-210S2's extra 30,000 BTU/h buys headroom rather than a second simultaneous fixture.
Efficiency is identical: UEF 0.96 at the high draw class on both, so there is no efficiency argument between them. The physical difference is modest — the same cabinet dimensions, with the NPE-180S2 at 68 lb (30.8 kg) against the NPE-210S2's 73 lb (33.1 kg). The NPE-180S2 is the lightest S2 model.
The choice is a demand question. Small houses, suites and laneway homes with sequential demand fit the NPE-180S2 and its lower gas draw; a two-bathroom home that wants more winter headroom, or that is converting from a larger tank, is assessed against the NPE-210S2 or the flagship NPE-240S2. The gas supply and vent route are confirmed before either is specified, and whether CANRO stocks a model for a job is confirmed at consultation.
Navien · Gas tankless
The Navien NPE-180S2 is the smallest of Navien's current S2 condensing tankless models: 10,000–150,000 BTU/h on natural gas or propane, UEF 0.96, and published flows of 8.4 GPM at a 35 °F rise and 4.3 GPM at a 67 °F rise.
Navien · Gas tankless
The Navien NPE-210S2 is the middle of Navien's current S2 condensing tankless models: 12,000–180,000 BTU/h on natural gas or propane, UEF 0.96, and published flows of 10.1 GPM at a 35 °F rise and 5.3 GPM at a 67 °F rise.
Neither. Both are rated UEF 0.96 at the high draw class on Navien's specification table; the difference between them is input and flow, not efficiency.
At its 67 °F-rise rating of 4.3 GPM it is marginal for two shower-class fixtures at once in January; the honest option for that demand is the NPE-210S2 or a larger S2 model, confirmed by a demand assessment.
They share the S2 venting and 3/4 in connection pattern, but the gas line and meter are sized to the input: 150,000 BTU/h on the NPE-180S2 against 180,000 BTU/h on the NPE-210S2. A supply check is part of the assessment.
A consultation includes a hot-water demand review so capacity is right for your winter, not the brochure's.
On-site service in Metro Vancouver, BC. Call to check availability.
Sources and verification
Facts checked September 7, 2026. Last updated September 20, 2026. Technical reviewer: not yet assigned.