A real, honest brand-by-brand comparison. Not "Rheem wins everything" — because they don't. Each major tankless brand has genuine strengths and real tradeoffs. The right brand depends on your specific install, your local dealer network, and what you value most: warranty, performance, parts availability, or price. Here's where each one lands.
If you want a sales pitch, this isn't it. If you want to make an informed decision, keep reading.
For most US homeowners, Rheem and Rinnai are the two safest picks — strong dealer networks, mature parts availability, predictable performance. Navien wins on raw efficiency and condensing technology but has a more complex install and historically tougher service support. Noritz is the contractor's favorite for reliability but priced higher. Bosch targets the budget end with smaller capacity. A.O. Smith is essentially the same product as Rheem under the hood (same parent company). Pick based on local dealer support before brand loyalty.
High-level snapshot before we dive into each brand. Pricing is for typical condensing whole-home models.
| Brand | Best For | Heat Exch. Warranty | Typical Price | Dealer Network |
|---|---|---|---|---|
| Rheem USA · founded 1925 | Balanced choice; best dealer network | 15 years | $1,000–$1,700 | Excellent (national) |
| Navien South Korea · founded 1978 | Max efficiency, condensing tech | 15 years | $1,200–$2,000 | Good (urban / coastal strong) |
| Rinnai Japan · founded 1920 | Reliability; long track record | 12–15 years | $1,100–$1,800 | Excellent (national) |
| Noritz Japan · founded 1951 | Pro-grade reliability, contractor favorite | 12 years | $1,300–$2,100 | Moderate (varies by region) |
| Bosch Germany · founded 1886 | Compact / point-of-use installs | 10–12 years | $700–$1,300 | Limited (Lowe's primary) |
| A.O. Smith USA · founded 1874 | Same as Rheem — sister brand | 15 years | $1,000–$1,700 | Excellent (commercial-leaning) |
Pricing reflects typical online retail for whole-home condensing units. Add 30–60% for installation cost depending on complexity.
Rheem is the largest North American tankless brand by installed base. The RTGH series (condensing) and RTG series (non-condensing) cover essentially every install scenario, with the recently updated IKONIC series (RTGH-SR10i / SR11i) sitting at the premium end with built-in recirculation. The standout is the 15-year heat exchanger warranty — tied for longest in the industry — and the dealer network that means parts and service are available essentially everywhere in the US.
Rinnai has the longest tankless track record in North America and the cleanest reliability data. Their RX series (non-condensing) and RU/RSC series (condensing) are workhorses — not the most innovative, but rarely the source of warranty calls either. Plumbers who install one brand often install Rinnai because they know exactly what they're getting. The tradeoff: pricing is similar to Rheem, but features are a half-step behind on the latest releases.
Noritz is the brand professional installers recommend when they're not constrained by what's on the truck. The EZ series and EZTR series are widely considered the most install-friendly in the category — clear documentation, accessible service ports, modular components. The downside is price (typically the highest of the major brands) and a smaller dealer network than Rheem or Rinnai, which means fewer DIY-supportive resources online.
Bosch's tankless lineup is more limited than the Asian brands and targets the budget and point-of-use end of the market. The Greentherm and Therm series are smaller, lower-BTU units that fit well for ADUs, smaller homes, or point-of-use installs. Sold primarily through Lowe's, which means easy retail access but less depth of service support compared to brands sold through plumbing supply houses.
Here's something most brand comparison articles miss: A.O. Smith and Rheem source significant components from the same supply chain, and their tankless units share a lot of underlying engineering. A.O. Smith's tankless lineup (ATI series) is essentially the commercial-leaning sibling of the Rheem lineup. They lean more commercial / multi-family / light-commercial; Rheem leans more residential. For a typical homeowner, choosing between them comes down to which one your local supplier carries and at what price.
If you've made it this far, the brand comparison probably isn't quite as clear-cut as you hoped. That's because for most homeowners, brand is not actually the most important variable. Here's what matters more, in priority order:
The best tankless in the world is the one you can get serviced when it fails. Before committing to any brand, ask your local plumber what they install most. Whatever they're most comfortable with will get faster service, parts in hours rather than days, and warranty issues resolved without drama. A "lesser" brand with a great local installer beats a "better" brand with no local support every time.
An undersized Navien performs worse than a properly sized Bosch. Run the math from our sizing guide first. Pick the right size for your climate and household, then choose the brand within that size class.
The condensing decision affects your install cost more than the brand choice does. See our condensing vs. non-condensing breakdown.
Once you've nailed down size, fuel type, and condensing/non-condensing, then compare brand options at that spec. Rheem, Rinnai, and Navien will all have a competitive product at any given spec — pick based on warranty terms, your installer's preference, and price.
Tell us your install scenario — climate, fuel, bathroom count, who your local installer is — and we'll give you our honest recommendation. Sometimes that's Rheem, sometimes it's another brand we don't sell, and we'll tell you straight either way. Call 877-881-2742. RheemTanklessOnline.com is operated by LCP Supply alongside our flagship plumbing wholesaler PlumbersCrib.com — every Rheem order is fulfilled by an authorized dealer with full manufacturer warranty support.