Navien NPE-S2 Series
High-Efficiency Condensing Tankless Water Heater
Navien NPE-S2 -- Premium Efficiency at a Smarter Price
The Navien NPE-S2 delivers nearly identical performance to the flagship NPE-A2 at a lower price point. It achieves up to 0.96 energy factor -- just one point below the A2 -- and shares the same advanced condensing technology, NaviLink Wi-Fi connectivity, ComfortFlow temperature management, and PVC venting compatibility.
The key difference is the recirculation pump. While the NPE-A2 includes a built-in pump and buffer tank for instant hot water, the NPE-S2 offers recirculation as an optional add-on. If instant hot water is not a top priority for your household, or if you would like the flexibility to add it later, the NPE-S2 is an excellent choice that saves you money upfront without sacrificing efficiency.
All Island Comfort installs every NPE-S2 size across all of Long Island. Every installation includes PVC venting, gas line connection, a condensate neutralizer, electrical hookup, and complete system testing.
Like the A2, the NPE-S2 is available in four sizes -- 150,000, 180,000, and 199,900 BTU -- with the same compact 17.3" x 27.4" wall-mount footprint. The biggest advantage of the S2 is flexibility: you get condensing-level efficiency right away, and if you decide later that you want instant hot water, the external recirculation pump can be added without replacing the unit.
Navien backs the NPE-S2 with a 15-year heat exchanger warranty, 5 years on parts, and 1 year on labor -- the same coverage as the flagship A2. With annual maintenance including heat exchanger flushing and filter cleaning, the S2 is built to last 20 years or more, making it one of the best long-term values in tankless water heating.
Near-identical efficiency to the A2
Add a pump now or retrofit later
Monitor and control from your phone
Same condensing tech, smarter price
Inside the NPE-S2
2" PVC Up to 75 Feet
1/2" gas up to 24 feet -- affordable PVC venting eliminates the need for expensive stainless steel
High Efficiency Up to 0.96 UEF
Up to 15:1 turndown ratio for precise temperature control across a wide range of flow rates
Dual Stainless Steel Heat Exchangers
Durable dual heat exchangers maximize heat transfer and resist corrosion for long-lasting performance
EZNav™ Multi-Line Control
Built-in intuitive software with multi-line display for easy setup, diagnostics, and temperature adjustment
NPE-S2 Full Specifications
| Type | Condensing Tankless Water Heater |
|---|---|
| Placement | Indoor / Outdoor |
| Energy Factor | Up to 0.96 EF / 0.96 UEF |
| Turndown Ratio | Up to 15:1 |
| BTU Input Range | 13,300 -- 199,900 BTU/h (NPE-240S2) |
| Max Flow Rate (35°F rise) | 11.2 GPM (NPE-240S2) |
| Max Flow Rate (45°F rise) | 8.7 GPM (NPE-240S2) |
| Max Flow Rate (67°F rise) | 5.6 GPM (NPE-240S2) |
| Recirculation Pump | Optional external (sold separately) |
| Wi-Fi Control | NaviLink compatible |
| ComfortFlow | Yes (with optional recirc pump) |
| Venting | 2" PVC up to 75 ft; 1/2" gas up to 24 ft |
| Heat Exchangers | Dual stainless steel |
| Control Panel | EZNav™ multi-line with intuitive software |
| Condensate Neutralizer | Required |
| Gas Types | Natural Gas or Liquid Propane |
| Gas Pressure (NG) | 3.5" WC minimum |
| Gas Pressure (LP) | 11.0" WC minimum |
| Gas Line Size | 3/4" minimum |
| Electrical | 120V, 60Hz dedicated outlet |
| Dimensions (W x H x D) | 17.3" x 27.4" x 13.2" |
| Weight (NPE-240S2) | 73 lbs |
| Heat Exchanger Warranty | 15 years |
| Parts Warranty | 5 years |
| Labor Warranty | 1 year |
| Installed From | $7,800 |
Available NPE-S2 Sizes
The NPE-S2 is available in four sizes. All share the same physical dimensions and feature set -- the difference is heating capacity and flow rate.
NPE-150S2
- 8.4 GPM at 35°F rise
- 6.5 GPM at 45°F rise
- Weight: 62 lbs
Best for: 1-2 bathroom homes
NPE-180S2
- 9.8 GPM at 35°F rise
- 7.6 GPM at 45°F rise
- Weight: 68 lbs
Best for: 2-3 bathroom homes
NPE-210S2
- 10.1 GPM at 35°F rise
- 7.8 GPM at 45°F rise
- Weight: 73 lbs
Best for: 3 bathroom homes
NPE-240S2
- 11.2 GPM at 35°F rise
- 8.7 GPM at 45°F rise
- Weight: 73 lbs
Best for: 3-4+ bathroom homes
Not sure which size fits your home? We will measure your peak hot water demand during a free site assessment. Call (631) 591-2289 to schedule.
NPE-S2 Key Features
Condensing Efficiency Up to 0.96
The NPE-S2 uses dual stainless steel heat exchangers to extract maximum energy from combustion gases before they are vented. At 0.96 energy factor, it converts 96 cents of every dollar you spend on gas into hot water -- significantly more efficient than non-condensing models (0.82) and traditional tank heaters (0.60 to 0.67).
Optional Recirculation Pump
Unlike the NPE-A2 which has a built-in pump, the NPE-S2 supports an optional external recirculation pump and buffer tank. This gives you the flexibility to skip it if instant hot water is not a priority, or add it during installation or at any point in the future.
NaviLink Wi-Fi Connectivity
Connect your NPE-S2 to your home Wi-Fi network and manage it from anywhere with the NaviLink app. Adjust temperature settings, set recirculation schedules (if equipped), monitor performance, and receive maintenance alerts -- all from your phone.
ComfortFlow Technology
When paired with the optional recirculation pump and buffer tank, the NPE-S2's ComfortFlow system eliminates the "cold water sandwich" effect. It uses a mixing valve to ensure consistent water temperature between draws, so you never get that surprise burst of cold water.
PVC Venting Up to 60 Feet
Because exhaust temperatures are low on condensing units, the NPE-S2 uses standard PVC pipe for venting instead of expensive stainless steel. Concentric venting runs up to 60 feet and two-pipe configurations up to 150 feet, giving our installers flexibility for placement in your Long Island home.
Cascading for High Demand
For larger homes or properties with unusually high hot water demand, multiple NPE-S2 units can be linked together in a cascading configuration. The units communicate with each other and share the load, providing seamless hot water delivery even during peak usage periods.
Smart Control with NaviLink Wi-Fi
The NPE-S2 connects to your home Wi-Fi through NaviLink, giving you full remote control from your phone. Adjust water temperature, monitor system performance, and receive maintenance alerts whether you are home or away. If you add the optional recirculation pump, you can also program hot water schedules directly from the app.
When an error code appears, the NaviLink app displays it immediately -- no need to walk to the unit to check the display. The app also logs performance data over time, which helps our technicians at All Island Comfort diagnose issues faster when you call for service.
How the NPE-S2 Compares
See how the NPE-S2 stacks up against the other Navien residential models. For a full breakdown, visit our complete model comparison page.
| Feature | NPE-A2 | NPE-S2 | NHW-AI | NHW-AE |
|---|---|---|---|---|
| Type | Condensing | Condensing | Non-Condensing | Non-Condensing |
| Energy Factor | Up to 0.97 | Up to 0.96 | Up to 0.82 | Up to 0.82 |
| Max Flow Rate | 11.2 GPM | 11.2 GPM | 9.5 GPM | 9.5 GPM |
| Recirculation | Built-in | Optional | No | No |
| Wi-Fi Control | Yes | Yes | No | No |
| Venting | PVC | PVC | Stainless Steel | Not Required |
| Neutralizer Needed | Yes | Yes | No | No |
| Installed From | $7,900 | $7,800 | $4,540 | $4,040 |
What Is Included with NPE-S2 Installation
Navien NPE-S2 Unit
Factory-new unit in the size recommended for your home.
PVC Venting
Concentric or two-pipe PVC venting installed per Navien specs.
Gas Line Connection
Professional 3/4" gas line connection with pressure testing.
Condensate Neutralizer
Required for all condensing models. Installed and pH-tested.
Electrical Connection
Dedicated 120V outlet for controls and ignition system.
Water Lines + Isolation Valves
Hot and cold connections with service valves for future maintenance.
Full System Testing
Every fixture tested, gas pressure verified, leak-checked, error-free startup.
Warranty Registration
We register your unit to activate the full 15-year manufacturer warranty.
Explore Other Navien Models
NPE-A2 Series
Premium condensing with built-in recirculation for instant hot water. Up to 0.97 EF. Starting at $7,900 installed.
View NPE-A2 Non-CondensingNHW-AI Series
Indoor non-condensing, budget-friendly entry into tankless. Up to 0.82 EF. Starting at $4,540 installed.
View NHW-AI Non-CondensingNHW-AE Series
Outdoor non-condensing with weatherproof housing. No venting needed. Starting at $4,040 installed.
View NHW-AENPE-S2 Frequently Asked Questions
What is the difference between the NPE-S2 and the NPE-A2?
The main difference is the recirculation pump. The NPE-A2 has a built-in recirculation pump and 0.5-gallon buffer tank that delivers near-instant hot water at every faucet. The NPE-S2 does not include a built-in pump but supports an optional external pump that can be added during or after installation. The NPE-S2 costs $100 less installed and achieves a very similar energy factor (0.96 vs 0.97).
Can I add a recirculation pump to the NPE-S2 later?
Yes. The NPE-S2 is designed to work with Navien's optional external recirculation pump and buffer tank accessory. It can be added during your initial installation or retrofitted at any point in the future. Adding it later does require additional plumbing and electrical work, so it is more cost-effective to include it during the original installation if you know you want it.
Does the NPE-S2 require a condensate neutralizer?
Yes. As a condensing unit, the NPE-S2 produces acidic condensate (pH 3-5) that must be neutralized before entering your drain system. This is required by Long Island building codes. We include condensate neutralizer installation with every NPE-S2 installation at no additional charge.
How much does a Navien NPE-S2 cost installed?
NPE-S2 installation starts at $7,800 installed, which includes the unit, gas line connection, PVC venting, condensate neutralizer, electrical connection, water lines, full system testing, and warranty registration. That is $100 less than the NPE-A2. Financing is available starting at 0% APR through Wisetack.
What size NPE-S2 do I need?
For 1-2 bathroom homes, the NPE-150S2 is typically sufficient. For 2-3 bathrooms, go with the NPE-180S2 or NPE-210S2. For 3-4+ bathrooms or high-demand homes, the NPE-240S2 at 199,900 BTU and 11.2 GPM provides maximum capacity. Our technicians will measure your actual demand during a free site assessment. Call (631) 591-2289 to schedule.
Is the NPE-S2 worth it over a non-condensing model?
For most Long Island homeowners, yes. The NPE-S2 costs more upfront ($7,800 vs $4,540 for the NHW-AI), but its 0.96 energy factor vs 0.82 means significantly lower monthly gas bills. It also uses cheaper PVC venting instead of stainless steel, includes Wi-Fi monitoring, and offers the option to add recirculation for instant hot water. Over the 20+ year lifespan of the unit, the energy savings typically more than offset the higher purchase price.
What maintenance does the NPE-S2 need?
Navien recommends annual maintenance including flushing the heat exchanger with vinegar solution (about 45 minutes), cleaning the inlet water filter, inspecting PVC venting, and checking the condensate neutralizer media. Our repair and maintenance team handles all of this. Regular maintenance keeps your unit running at peak efficiency and protects your warranty.
Does the NPE-S2 work with propane?
Yes. The NPE-S2 is available in both Natural Gas (NG) and Liquid Propane (LP) versions. LP models require different gas pressure settings (11.0" WC vs 3.5" WC for natural gas), which we configure during installation. Both versions deliver the same performance and efficiency ratings.
Ready to Install an NPE-S2?
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