Navien and Rinnai are two of the most widely installed tankless water heater brands in North America, and both build reliable equipment. If you're replacing a tank or upgrading an older tankless unit, the "right" choice usually depends less on the logo and more on your installation: your venting route, whether you need recirculation, your gas supply, and which brand local installers know best.
This guide compares the two brands on the points that matter: condensing vs non-condensing lines, efficiency (UEF), venting, recirculation and published warranty terms. We sell Navien, and we say so up front. We've kept this comparison to facts each manufacturer publishes, so you can make your own call.
Quick overview of each brand's lineup
Navien
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NPE-2 series (condensing): Navien's main residential condensing line, sold in two versions.
- NPE-S2 (standard): Rated at 0.96 UEF.
- NPE-A2 (ComfortFlow): Adds a built-in buffer tank and recirculation pump. Rated at 0.95 UEF.
- NHW series (non-condensing): A compact line with a stainless steel heat exchanger. Navien lists 0.81 UEF across the NHW models. It comes as the NHW-SU (indoor/outdoor) and the NHW-AI (indoor, with a built-in recirculation pump and buffer tank).
Rinnai
- SENSEI RX series (condensing): Rinnai's residential condensing line. Rinnai lists up to 0.98 UEF on select RX models. Models with a "P" in the name (such as the RXP) include a built-in recirculation pump.
- RE series (non-condensing): Rinnai's current non-condensing residential line. Pump-equipped REP models offer Rinnai's Smart-Circ recirculation, which learns your household's hot water routine.
Both brands also sell commercial and boiler-combi products, which are beyond the scope of this guide.
Condensing vs non-condensing: the biggest decision
Before you choose a brand, decide whether you want a condensing or a non-condensing unit. This choice affects price, venting and efficiency more than brand does.
| Condensing (Navien NPE-2, Rinnai SENSEI RX) | Non-condensing (Navien NHW, Rinnai RE) | |
|---|---|---|
| Efficiency | Higher: roughly 0.95 – 0.98 UEF | Lower: about 0.81 UEF on the models cited above |
| Venting | Plastic vent pipe (PVC/CPVC/polypropylene), as allowed by the manual | Brand-specific concentric vent or stainless steel vent |
| Condensate drain | Required (a neutralizer is usually recommended) | Not required |
| Up-front cost | Higher | Lower |
| Best for | Long-term efficiency, flexible indoor venting | Tight budgets, outdoor installs, simple replacements |
If you're replacing an existing non-condensing unit and the vent is already in place, a like-for-like replacement is often the simplest job. If you're converting from a tank heater, a condensing unit with plastic venting can be easier to route through a sidewall.
Efficiency (UEF) compared
UEF (Uniform Energy Factor) is the Department of Energy rating for water heater efficiency. Higher is better. On condensing models, the two brands are close:
- Navien NPE-S2: 0.96 UEF. NPE-A2: 0.95 UEF. Figures are from Navien's published specifications.
- Rinnai SENSEI RX: Varies by model. Rinnai lists 0.98 UEF on its RX199iN, and some other RX models are rated around 0.96–0.97.
In practice, a few hundredths of a point in UEF makes a modest difference to your yearly energy bill. Correct sizing, gas supply and a good install usually matter more. Check the exact model's rating on the manufacturer's spec sheet or in the ENERGY STAR directory before you buy.
Venting
Venting is often the deciding factor because it drives installation cost.
- Navien NPE-2: Navien lists 2" vent material with a maximum length of 75 feet, with length deductions for elbows. Approved materials include PVC Schedule 40, CPVC Schedule 80, approved polypropylene and stainless steel. Navien's installation manual covers other vent sizes and lengths. The ability to use 2" PVC is a big advantage when you replace an old tank heater and need to snake a new vent through tight framing.
- Navien NHW-SU: Navien lists a 3" x 5" concentric vent system.
- Rinnai SENSEI RX: Condensing, so it vents with plastic pipe as allowed by its installation manual. Check Rinnai's manual for the approved materials, diameters and maximum lengths for your model.
- Rinnai RE/REP: Non-condensing models use a concentric vent system. Rinnai lists 3"/5" concentric venting for the REP models.
For a retrofit, ask your installer to price both brands with your actual vent route. The cheaper heater isn't always the cheaper install.
Recirculation: Navien ComfortFlow vs Rinnai recirculation
Recirculation keeps hot water close to your fixtures so you wait less at the tap. Both brands offer it built in, but they approach it a little differently.
Navien ComfortFlow (NPE-A2 and NHW-AI)
Navien's ComfortFlow models add a built-in recirculation pump and a small buffer tank. The buffer tank helps reduce the "cold water sandwich," a short burst of cold water you can get when a tankless unit restarts between uses. The unit's controls let you choose how and when recirculation runs. Navien's installation manual covers piping for homes with and without a dedicated hot water return line.
If you don't need recirculation, the standard Navien NPE-240S2 keeps things simple. If you do need it, the Navien NPE-240A2 with ComfortFlow builds it into the same footprint.
Rinnai recirculation (RXP and REP models)
Rinnai's pump-equipped models (the "P" versions) include a built-in recirculation pump. On the RE series, Rinnai's Smart-Circ feature learns your hot water usage over time and schedules recirculation around it, with no external controller needed. As with Navien, homes without a dedicated return line typically need a crossover valve accessory.
Both systems do the same core job. The difference is mostly in the buffer tank (a Navien ComfortFlow feature) and in each brand's scheduling and app approach.
Warranty terms as published
Warranty terms change, depend on the exact model and installation, and often require registration. Treat the figures below as a summary of what each brand publishes, and always read the current warranty document for your specific model.
- Navien (NPE condensing series, residential): Navien's published warranty for standard or controlled recirculation installs is 15 years on the heat exchanger, 5 years on parts and 1 year on labor. Shorter terms apply to uncontrolled (continuous) recirculation installs.
- Rinnai (SENSEI residential): Rinnai's published residential warranty is 15 years or 12,000 operating hours (whichever comes first) on the heat exchanger, and 5 years on other parts. Labor is covered for 5 years if the product is registered within 90 days of installation, otherwise 1 year.
Both brands require installation according to their instructions, and typically by a qualified professional. Improper installation, poor water quality, or missing descaling and maintenance can affect coverage.
Which should you buy?
Both brands make dependable tankless water heaters. Here's a practical way to decide:
- Choose Navien NPE-2 if you want 2" PVC venting flexibility, a buffer tank with built-in recirculation (NPE-A2), or you're converting from a tank and need an easy vent route.
- Choose Navien NHW if you want a compact non-condensing unit for a simpler or lower-cost install, including outdoor locations (NHW-SU).
- Choose Rinnai if your installer is factory-trained on Rinnai, you're replacing an existing Rinnai and want to reuse the vent and connections, or a specific RX model fits your efficiency target.
- Either way: Size the unit for your peak flow and winter temperature rise, confirm your gas line can supply the full BTU input, and use a licensed installer.
Ready to compare Navien models side by side? Browse our Navien tankless water heaters collection, with free shipping on qualifying orders. Not sure what size you need? Start with our tankless water heater sizing guide, or contact our team for help.