Canada-wide water heater information · On-site service in Metro Vancouver, BC
WaterHeating.ca is operated by CANRO Heating & Cooling
Comparison
Verdict in brief
These are the two current Navien flagship sizes at the same 13,300–199,900 BTU/h input and the same cabinet: the A2 series and its S2 successor. Navien rates the S2 at UEF 0.96 against the A2's 0.95 and publishes 5.8 GPM at a 67 °F rise against 5.6, while the A2 specification table is the one that lists a sub-0.01 GPM option in ComfortFlow mode. Both deliver their winter capacity at the flow-at-rise figure, not the 11.2 GPM headline. Choose the S2 as the current platform unless a specific reason keeps the A2 in play.
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-240A2Gas tankless | Navien NPE-240S2Gas tankless |
|---|---|---|
| Minimum gas input | 13,300 BTU/h | 13,300 BTU/h |
| Maximum gas input | 199,900 BTU/h | 199,900 BTU/h |
| Flow at a 35 °F (19.4 °C) rise | 11.2 GPM (42.4 L/min) at 35 °F (19.4 °C) rise | 11.2 GPM (42.4 L/min) at 35 °F (19.4 °C) rise |
| Flow at a 45 °F (25 °C) rise | 8.7 GPM (32.9 L/min) at 45 °F (25 °C) rise | 8.7 GPM (32.9 L/min) at 45 °F (25 °C) rise |
| Flow at a 67 °F (37.2 °C) rise | 5.6 GPM (21.2 L/min) at 67 °F (37.2 °C) rise | 5.8 GPM (22.0 L/min) at 67 °F (37.2 °C) rise |
| Minimum flow rate | 0.5 GPM (1.9 L/min); under 0.01 GPM option in ComfortFlow mode | 0.5 GPM (1.9 L/min) |
| Uniform Energy Factor (UEF) | 0.95 | 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; up to 200 W (2 A), 350 W (4 A) with external pump | 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 | 77 lb (34.9 kg) | 73 lb (33.1 kg) |
“—” 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 input class is identical: 13,300–199,900 BTU/h on natural gas or propane on both. The published flows match at a 35 °F rise (11.2 GPM / 42.4 L/min) and a 45 °F rise (8.7 GPM / 32.9 L/min), and separate only at the 67 °F row, where the S2 is rated 5.8 GPM (22.0 L/min) against the A2's 5.6 GPM (21.2 L/min). Metro Vancouver's winter rise to a 49 °C shower approaches 40 °C (72 °F), so that row is the sizing number, not the 35 °F maximum.
Efficiency differs by one point: UEF 0.96 on the S2 against 0.95 on the A2, both high-draw-class tankless ratings. The direction is real, but a one-point UEF difference is not a savings percentage and is not compared with a storage tank's UEF at a different draw pattern.
Physically they share the cabinet at 17.3 in wide, 27.4 in high and 13.2 in deep, with the S2 listed lighter at 73 lb (33.1 kg) than the A2 at 77 lb (34.9 kg). Both connect to 3/4 in gas and 3/4 in water, vent in 2 in or 3 in PVC, CPVC, approved polypropylene or stainless steel (or BH special gas vent) as a forced-draft direct vent, and run on 120 V AC.
Minimum flow is 0.5 GPM (1.9 L/min) on both, with the A2 specification table adding a sub-0.01 GPM option in ComfortFlow recirculation mode. That only matters for very low-flow fixtures; neither unit fires a trickle at the tap without recirculation configured.
Navien's Canadian site lists both the NPE-A2 and NPE-S2 series, with the S2 the newer line. Navien's published resale policy voids warranty for internet or e-commerce purchases and supply runs through contractors, so whether CANRO stocks a given model for a specific job is confirmed at consultation.
Navien · Gas tankless
The Navien NPE-240A2 is the largest of Navien's Canadian A2 condensing tankless models: 13,300–199,900 BTU/h on natural gas or propane, UEF 0.95, and published flows of 11.2 GPM at a 35 °F rise and 5.6 GPM at a 67 °F rise. It is a wall-hung, forced-draft direct-vent unit.
Navien · Gas tankless
The Navien NPE-240S2 is the largest of Navien's current S2 condensing tankless models: 13,300–199,900 BTU/h on natural gas or propane, UEF 0.96, and published flows of 11.2 GPM at a 35 °F rise and 5.8 GPM at a 67 °F rise.
The S2 is the current platform with the higher published UEF (0.96 against 0.95) and slightly higher flow at a 67 °F rise (5.8 against 5.6 GPM). The A2 remains valid where it is already specified or where it fits the budget and supply.
They share the same input and the same flow at 35 °F and 45 °F rises, and differ only slightly at the 67 °F winter-class row. Both are sized from flow at the rise the home actually sees.
Yes. Both are forced-draft direct-vent units taking 2 in or 3 in PVC/CPVC/approved polypropylene or stainless (or BH special gas vent) and running on 120 V AC.
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 19, 2026. Last updated September 19, 2026. Technical reviewer: not yet assigned.