5 Best Tankless Water Heater Brands for 2026

Table of Contents

• How We Evaluated the Best Tankless Water Heater Brands
• 1. Rinnai: Best for Smart Home Integration
• 2. Navien: Best for High-Volume Hot Water Demand
• 3. Rheem: Best Value Tankless Water Heater
• 4. Noritz: Best for Commercial-Grade Durability
• 5. A.O. Smith: Best for Standard Residential Replacements
• How to Size a Tankless Water Heater for Your Home
• Tankless Water Heater Installation Cost and Retrofitting
• Frequently Asked Questions

Last Updated: September 12, 2026

How We Evaluated the Best Tankless Water Heater Brands

The best tankless water heater brands for 2026 are Rinnai, Navien, Rheem, Noritz, and A.O. Smith, ranked here on heat exchanger longevity, flow rate at real-world temperature rise, venting flexibility, smart controls, and how easy each unit is to service. This guide weighs the specs that decide whether a unit actually keeps up with your household.

We built these rankings around the factors that drive callbacks: parts availability, condensing versus non-condensing venting requirements, and whether a manufacturer's service network reaches your area. Rinnai takes the top spot overall, Navien leads for high demand, and Rheem wins on value.

Quick Picks:

• Best Overall: Rinnai, best smart home integration and service network
• Best for High Demand: Navien, dual heat exchangers and built-in recirculation
• Best Value: Rheem, strong mid-tier performance at retail pricing
• Best Commercial-Grade: Noritz, quick-connect manifold systems for multi-unit setups
• Best for Standard Replacements: A.O. Smith, straightforward, Energy Star certified models

1. Rinnai: Best for Smart Home Integration

Rinnai is the best tankless water heater brand for homeowners who want app-based control and faster hot water delivery. Its Smart-Circ technology learns your usage patterns and keeps a small reserve of hot water ready, which cuts the cold-water sandwich effect common in long pipe runs.

The Control-R module adds Wi-Fi monitoring, so you can adjust temperature and run diagnostics from a phone. Units ship in both condensing and non-condensing configurations, which matters when venting material and installation permit requirements limit your options.

What works: An extensive service network means parts and qualified technicians are rarely a problem. What doesn't: the initial investment runs higher than entry-level brands, and the smart features only pay off if you'll actually use them.

2. Navien: Best for High-Volume Hot Water Demand

Navien earns its place with dual stainless steel heat exchangers, a design choice that adds longevity in hard water conditions where scale buildup shortens the life of single-exchanger units. Select models include a built-in recirculation pump, which delivers near-instant hot water without adding an external pump.

For multi-unit buildings, common venting capabilities let several heaters share one vent run. That simplifies retrofits where running separate vents would be cost-prohibitive.

The tradeoff is service dependency. These units are not DIY-friendly, and skipping annual descaling on a condensing model invites flow sensor faults and error codes that require a technician.

3. Rheem: Best Value Tankless Water Heater

Rheem balances performance and price better than almost anyone in the mid-tier. Retail availability is the real advantage: you can buy a unit at a major home improvement store, which shortens lead times during an emergency replacement.

EcoNet Wi-Fi connectivity handles remote temperature control, and the self-diagnostic system with digital display surfaces fault codes without a service call. Gas and electric configurations cover most residential scenarios.

The catch: electric models draw heavy amperage and often require a panel upgrade to meet voltage requirements. Factor that into the total before you commit.

4. Noritz: Best for Commercial-Grade Durability

Noritz builds gas-fired units around commercial-grade heat exchangers, and it shows in high-demand homes with multiple simultaneous showers. Quick-connect technology links two or more heaters into a single manifold system, scaling capacity without a custom engineering job.

Low-NOx emission designs suit jurisdictions with stricter air quality rules, and the build quality holds up under continuous duty.

Availability is the weak point. Fewer retail outlets stock Noritz, so sourcing a replacement on short notice takes longer than it does for Rheem.

5. A.O. Smith: Best for Standard Residential Replacements

A.O. Smith is the straightforward pick for replacing an aging tank with a like-for-like tankless swap. Energy Star certified models, user-friendly digital temperature controls, and a compact wall-mounted footprint make installation predictable.

This is not the brand for someone chasing smart-home integration. There are fewer connected features here than on Rinnai or Rheem units, and that's a deliberate trade: fewer electronics means fewer failure points.

For property managers standardizing across multiple units, that simplicity is a feature, not a limitation.

How to Size a Tankless Water Heater for Your Home

Sizing a tankless water heater means matching its flow rate in gallons per minute to the combined demand of every fixture you might run at once, adjusted for your incoming water temperature. Undersize the unit and you get lukewarm showers; oversize it and you pay for capacity you never use. The math is simple enough to do yourself, and doing it before you shop prevents the most expensive mistake in this category.

Step 1: Add up the fixtures you would realistically run simultaneously. Use the flow ratings on the fixtures themselves where you can find them, or these typical ranges:

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• Showerhead: roughly 2.0 to 2.5 GPM
• Kitchen faucet: roughly 1.5 to 2.2 GPM
• Bathroom faucet: roughly 0.5 to 1.5 GPM
• Washing machine: roughly 2.0 to 2.5 GPM
• Dishwasher: roughly 1.0 to 2.0 GPM

A two-shower household with a kitchen faucet running is roughly 6.5 to 7.2 GPM at peak. That peak number, not the total fixture count, is what the unit has to satisfy.

Step 2: Calculate temperature rise. Temperature rise is your target output temperature minus the incoming groundwater temperature. If you want 120°F at the tap and your incoming water is 50°F in winter, the rise is 70°F (energy.gov). In summer the same groundwater might be 65°F, so the rise drops to 55°F and the unit produces more hot water from the same flow rating. This is why a unit that performs well in July can fall short in January.

Step 3: Read the flow rating at your actual temperature rise, not the headline number. Manufacturers publish GPM at a specific rise, often 35°F or 45°F. A unit rated at 9 GPM at a 35°F rise does not deliver 9 GPM at a 70°F rise, it delivers roughly half. Always find the GPM figure at the rise your climate produces in the coldest month, because that is the number that determines whether your shower stays hot.

Step 4: Check first-hour rating and recovery rate. Those numbers tell you how the unit performs under sustained draw, not just at peak. A unit can hit its rated flow for a short burst and then fall off; the first-hour rating shows what it can sustain.

A Department of Energy guide to tankless water heaters explains how energy factor and thermal efficiency ratings translate into real operating costs, which matters once you have narrowed the field to two or three units that all meet your flow requirement.

Step 5: Match the unit type to your climate and fuel. Gas units generally deliver higher flow at a given temperature rise than electric units, which is why gas dominates in cold climates. Electric units are viable in warm regions or for single-fixture applications, but a whole-home electric unit in a cold climate often needs more amperage than a residential panel can supply.

Tankless Water Heater Installation Cost and Retrofitting

Tankless water heater installation cost depends less on the unit than on what your home requires to support it. Retrofitting from a tank system typically involves new venting, a gas line upgrade, and sometimes an electrical circuit, none of which appear on the box price. The unit itself is often the smallest line item on the invoice.

Gas line capacity is the most common hidden cost. A tankless gas unit fires at a much higher BTU input than a tank because it has to heat water instantaneously rather than store it. A standard residential gas line and meter may not deliver enough volume at the required pressure, so the plumber has to upsize the run from the meter or add a dedicated line. That work is billed by the linear foot plus fittings and a shutoff, and it is the single line item most likely to push a retrofit over budget.

Venting material is the second hidden cost, and it is dictated by the unit type.

• Condensing units recover heat from exhaust, so flue gas exits cool enough for PVC or CPVC venting. PVC is inexpensive and easy to route, but the unit produces acidic condensate that must drain to a neutralizer or a suitable drain. If no drain is nearby, a condensate pump and a new drain line get added to the job.
• Non-condensing units exhaust hot enough to require stainless steel venting, which costs substantially more per foot than PVC and needs greater clearance from combustibles. In some homes the only viable route is a sidewall termination, which triggers local clearance rules for windows, doors, and intakes.

Electrical service matters even on gas units. A tankless gas heater still needs a dedicated 120-volt circuit for the control board, fan, and ignition. Electric tankless models are a different problem entirely: they draw high amperage at 240 volts, and many homes do not have the spare capacity in the existing panel. A service upgrade or a subpanel is common, and that work is performed by an electrician, not the plumber, so it lands as a separate invoice.

Permits and inspection add time, not just money. Most jurisdictions require a plumbing permit for a water heater replacement, and a gas line modification or new vent often pulls a mechanical permit as well. The inspection has to happen before the job is considered closed, which can add days to the schedule depending on the local inspection queue.

New construction versus retrofit changes the math completely. In new construction, the gas line, vent, and condensate drain are roughed in during framing, when the walls are open and the labor is incremental. In an existing home, the same work means opening finished walls, routing around obstructions, and patching afterward. The location of the unit relative to exterior walls and the gas meter drives most of the labor, which is why two homes with identical floor plans can get very different quotes.

Water quality belongs in this budget conversation. Hard water accelerates scale buildup inside the heat exchanger, and scale is the leading cause of premature failure on condensing units. A water softener installed upstream, or a scheduled descaling routine, extends unit life considerably and is far cheaper than a heat exchanger replacement. A EPA overview of water hardness and treatment covers how mineral content affects home water systems.

Smart home integration is cheapest at install time. Wi-Fi modules and recirculation pumps can be added while the technician already has the wall open and the lines accessible. Adding them later means a second service visit and, for a recirculation pump, a return line that may not exist. Decide before the technician closes up the wall.