If you want endless hot water without wasting space, low NOx non-condensing tankless water heaters are a smart upgrade for many homes. They’re built to deliver strong flow rates while keeping emissions lower than older gas models.
Below, we’ve focused on 10 options that stand out for real-world capacity, fuel compatibility, and install style, so you can narrow the field faster.
Best 10 Low Nox Non Condensing Tankless Water Heaters Picks for 2026
Outdoor Space-Saving Pick
Rinnai RE160eP 6.1 GPM Outdoor Propane Tankless
- Up to 6.1 GPM for multiple fixtures
- Non-condensing on-demand design saves energy
- Compact outdoor unit with LED service display
Best For: Outdoor propane installs that need a compact, efficient whole-home heater
High-Flow Outdoor Natural Gas Pick
Rheem RTG-84XLN-1 8.4 GPM Outdoor Natural Gas
- Ultra Low NOx burner technology
- High 8.4 GPM output for larger households
- Hot Start Programming and -30°F freeze protection
Best For: Outdoor natural gas homes needing strong flow and low-NOx operation
Smart Indoor Large-Family Pick
Mizudo 7.9 GPM Wi-Fi Propane Heater
- Sealed combustion design for indoor use
- Up to 7.9 GPM for 3 to 5 usage points
- Wi-Fi/app control plus safety protections
Best For: Indoor propane households wanting smart control and strong whole-home flow
Compact Everyday Value Pick
Rinnai V53DeP 5.3 GPM Propane Tankless
- 5.3 GPM for smaller hot-water demand
- Compact outdoor footprint
- Energy-saving on-demand heating with scale detection
Best For: Smaller propane households that want compact, efficient hot water
Smart Whole-Home Comfort
Westinghouse 7.9 GPM Natural Gas Indoor
- 7.9 GPM supports 3–5 fixtures
- ±1°F temperature stability
- WiFi app control and LED display
Best For: Indoor whole-home use with stable hot water and smart controls
High-Capacity Propane Pick
- 9.5 GPM for larger homes
- Hot-start programming reduces cold bursts
- Compact indoor wall-mount design
Best For: Propane households needing high-flow indoor hot water
Outdoor Ultra Low NOx Option
Rheem 9.5 GPM Natural Gas Outdoor
- Outdoor mount frees up indoor space
- 9.5 GPM and 199,900 BTUs
- EcoNet smart monitoring system
Best For: Outdoor natural gas installs that want high flow and smart monitoring
Indoor Wi‑Fi Output
- Up to 9.5 GPM for multiple hot water needs
- EcoNet Wi‑Fi remote control and monitoring
- LeakGuard leak detection and prevention system
Best For: Indoor whole-home use in 2–3 bathroom homes
High-Flow Smart Pick
- 10.3 GPM and 199,000 BTUs for large households
- WiFi/app control with ±1°F stability
- 16+ safety protections and sealed combustion
Best For: Large families needing high flow and app control
Outdoor Space Saver
- Up to 7.0 GPM for typical family demand
- Hot-start programming reduces cold bursts
- Outdoor wall-mount design saves indoor space
Best For: Homes wanting an outdoor non-condensing unit
Outdoor Space-Saving Pick – Rinnai RE160eP 6.1 GPM Outdoor Propane Tankless
If you’re comparing low nox non condensing tankless water heaters for an outdoor propane setup, the Rinnai RE160eP is built around compact size, on-demand heating, and straightforward serviceability. It delivers up to 6.1 GPM, heats only when needed to conserve energy, and includes an LED screen for reminders and error codes.
Best For: Outdoor installs where space savings and dependable whole-home hot water matter.
Pros:
- Compact outdoor design saves space while still supporting up to 6.1 GPM.
- Non-condensing, on-demand operation helps conserve energy by heating only when necessary.
- LED display provides service reminders and error codes for easier maintenance.
- Residential warranty coverage includes heat exchanger, parts, and labor terms when registered on time.
Cons:
- Professional installation is recommended by the manufacturer.
- Wi-Fi control requires the separate Controlr module.
- Outdoor installation only, so it is not a fit for indoor placements.
Overall, this Rinnai makes sense if you want a compact propane unit for outdoor use and value a trusted brand with service-focused design. Its output is strong enough for multiple fixtures, though buyers should plan for professional install and any optional smart controls separately.
High-Flow Outdoor Natural Gas Pick – Rheem RTG-84XLN-1 8.4 GPM Outdoor Natural Gas
Rheem RTG-84XLN-1 Mid-Efficiency 8.4GPM Outdoor Natural Gas Tankless Water Heater, Gray
Check Price On AmazonAmong low nox non condensing tankless water heaters, the Rheem RTG-84XLN-1 stands out for outdoor natural gas use and a high 8.4 GPM flow rate. It also includes Ultra Low NOx burner technology, Hot Start Programming to reduce cold bursts, and freeze protection rated down to -30 degrees.
Best For: Outdoor natural gas households that want high flow and low-emission burner tech.
Pros:
- Ultra Low NOx burner helps align with low-emission needs.
- 8.4 GPM output is strong for larger homes and multiple fixtures.
- Hot Start Programming helps minimize the cold water burst at startup.
- Freeze protection adds confidence for cold-weather outdoor installation.
Cons:
- Outdoor-only design limits placement options.
- Natural gas fuel type may not suit propane-only homes.
- It is a mid-efficiency model rather than a condensing unit.
For buyers prioritizing flow rate and outdoor durability, this Rheem is a practical fit. The low-NOx burner and freeze protection are useful extras, but the right choice depends on having natural gas available and an outdoor mounting plan.
Smart Indoor Large-Family Pick – Mizudo 7.9 GPM Wi-Fi Propane Heater
If you’re shopping low nox non condensing tankless water heaters for an indoor propane installation, the Mizudo 180,000 BTU model offers sealed combustion, app control, and steady output for larger households. It delivers up to 7.9 GPM, supports 3 to 5 usage points, and is built with safety features like freeze prevention and flue obstruction detection.
Best For: Indoor propane homes that want smart controls and whole-house hot water.
Pros:
- Closed combustion design draws external air and helps preserve indoor air quality.
- Up to 7.9 GPM supports multiple fixtures or 3 to 5 usage points.
- Wi-Fi and app control allow remote monitoring and convenient operation.
- CSA certification and multiple protection features add peace of mind.
Cons:
- Indoor installation means it is not the right choice for outdoor mounting.
- Requires 120V power and proper gas-line setup.
- Minimum activation flow and performance can vary with inlet water temperature.
This Mizudo is a strong fit if you want smart features alongside a sealed, space-saving indoor propane heater. Its output and protection package make it especially appealing for families, though the installation requirements are worth planning for in advance.
Compact Everyday Value Pick – Rinnai V53DeP 5.3 GPM Propane Tankless
For shoppers comparing low nox non condensing tankless water heaters in a simpler outdoor propane format, the Rinnai V53DeP focuses on efficient on-demand heating and a compact footprint. It offers 5.3 GPM, enhanced scale detection, and the kind of space-saving design that works well where installation room is limited.
Best For: Smaller households or lighter-demand propane setups that still want endless hot water.
Pros:
- On-demand propane heating helps conserve energy.
- Compact outdoor design fits tighter installation spaces.
- 5.3 GPM is a practical match for smaller homes or lower simultaneous demand.
- Enhanced scale detection is a helpful durability feature.
Cons:
- Lower flow rate than the larger units in this roundup.
- Outdoor installation only.
- Professional installation is recommended.
The V53DeP is the most straightforward pick here if you want a proven Rinnai propane unit without chasing maximum flow. It trades raw capacity for compact size and efficient operation, which can be a better fit for modest hot-water needs.
Smart Whole-Home Comfort – Westinghouse 7.9 GPM Natural Gas Indoor
If you want low nox non condensing tankless water heaters with strong whole-home capacity, this Westinghouse model is built for everyday residential use. It delivers up to 7.9 GPM and 180,000 BTU, making it a practical fit for homes that need reliable hot water for multiple fixtures without taking up much wall space.
Best For: Indoor installations where 3–5 fixtures may run at once and steady temperature control matters.
Pros:
- Up to 7.9 GPM and 180,000 BTU for whole-house hot water
- ±1°F temperature stability helps reduce noticeable swings during showers
- WiFi app control and LED display make adjustments simple
- Freeze protection and a copper heat exchanger support long-term indoor use
Cons:
- Requires indoor installation
- Designed for natural gas, so it is not a universal fuel choice
This is a solid pick if you want smart controls and consistent performance in a compact non-condensing tankless design. Its flow rate is enough for typical family demand, but the best fit is still a home with natural gas already in place.
High-Capacity Propane Pick – Rheem RTG 9.5 GPM Indoor LP
For shoppers comparing low nox non condensing tankless water heaters for larger households, this Rheem RTG series model stands out on flow rate. With up to 9.5 GPM and 199,900 BTUs, it is aimed at homes with multiple hot water demands, especially where propane is the preferred fuel and indoor installation is planned.
Best For: 2–3 bathroom homes that need high flow from an indoor liquid propane unit.
Pros:
- Up to 9.5 GPM handles heavier household demand
- 199,900 BTUs support fast hot water delivery
- Hot-start programming helps prevent cold bursts
- Compact wall-mount cabinet suits indoor installations
Cons:
- Indoor use only
- Requires liquid propane, not natural gas
- Installation should be handled by a qualified installer
This is the strongest fit here if flow rate is the top priority and propane is already part of your setup. It is a high-efficiency non-condensing option with useful comfort features, but the fuel type and indoor-only design narrow the audience.
Outdoor Ultra Low NOx Option – Rheem 9.5 GPM Natural Gas Outdoor
If your search for low nox non condensing tankless water heaters includes an outdoor setup, this Rheem model is the most installation-flexible of the group. It offers up to 9.5 GPM and 199,900 BTUs in a stainless steel outdoor cabinet, with EcoNet smart monitoring and a factory 120°F preset for straightforward operation.
Best For: Homes needing an outdoor natural gas tankless unit with smart monitoring and high flow.
Pros:
- Outdoor mount eliminates the need for indoor placement
- Up to 9.5 GPM supports strong whole-house demand
- EcoNet smart monitoring adds protection and convenience
- Stainless steel and copper construction support durability
Cons:
- Outdoor mount only
- Maximum temperature tops out at 140°F
- Uses fuel-powered natural gas, so it is not for propane setups
This is a practical choice when you want a non-condensing tankless heater outside the home and still want smart monitoring features. Its high flow and rugged build are appealing, but the outdoor-only format makes it best for specific installs.
Indoor Wi‑Fi Output – 9.5 GPM Natural Gas, Indoor
If you’re comparing low nox non condensing tankless water heaters for a medium-size household, this Rheem indoor model is built for steady whole-home supply. It delivers up to 9.5 GPM with 199,900 BTUs, so it fits homes with multiple bathrooms and recurring hot water demand like showers and laundry.
Best For: 2–3 bathroom homes that want indoor installation, Wi‑Fi control, and a high-output natural gas unit.
Pros:
- Up to 9.5 GPM helps support multiple simultaneous hot water uses.
- EcoNet Wi‑Fi allows remote control and monitoring.
- LeakGuard leak detection and prevention adds extra protection.
- Compact wall-mounted indoor design saves space.
Cons:
- Requires natural gas and professional installation.
- Indoor setup may not suit homes that need an outdoor unit.
- Higher-capacity output may be more than smaller households need.
Overall, this is a strong pick if you want a non-condensing tankless heater with good flow, smart controls, and indoor installation. It balances performance and convenience well for busy homes that need dependable hot water on demand.
High-Flow Smart Pick – 10.3 GPM Indoor Natural Gas
For shoppers evaluating low nox non condensing tankless water heaters for larger households, this Mizudo indoor model offers high flow and smart controls. It’s rated up to 10.3 GPM and 199,000 BTUs, with support for 5–7 usage points and ±1°F temperature stability.
Best For: Large families that want a high-flow indoor gas tankless unit with app control and built-in safety features.
Pros:
- 10.3 GPM capacity supports heavy whole-house demand.
- WiFi and app control make remote adjustment simple.
- 16+ safety protections, including freeze protection and anti-dry firing.
- ±1°F temperature stability helps reduce hot-cold swings.
Cons:
- Direct vent kit is sold separately.
- Indoor sealed combustion setup adds installation complexity.
- Requires 120V power and natural gas service.
This model stands out if you want maximum flow with smart convenience in a compact footprint. Its sealed combustion design and broad safety package make it a practical choice for demanding homes that still want precise temperature control.
Outdoor Space Saver – 7.0 GPM Natural Gas, Outdoor
If you’re sorting through low nox non condensing tankless water heaters for an outdoor install, this Rheem unit is a straightforward high-efficiency option. It provides up to 7.0 GPM and 160,000 BTUs, which is enough for many 2–3 bathroom homes with back-to-back showers and other common hot water uses.
Best For: Homes that want an outdoor natural gas tankless heater with reliable flow and simple wall mounting.
Pros:
- Up to 7.0 GPM covers typical family hot water demand.
- Hot-start programming helps prevent cold water bursts.
- Outdoor design frees up indoor space.
- Low activation flow rate and freeze protection add convenience.
Cons:
- Outdoor placement won’t work for every home layout.
- Lower flow than larger 9.5–10.3 GPM models.
- Natural gas installation still requires qualified setup.
This Rheem is a sensible choice if you want dependable non-condensing performance without an indoor cabinet. It keeps the feature set practical, with enough output for many households and extras that improve everyday use.
How We Picked the Best Low Nox Non Condensing Tankless Water Heaters
We selected low NOx non-condensing tankless water heaters based on usable flow rate, BTU output, fuel type, indoor or outdoor installation, and features that matter to homeowners such as temperature stability and WiFi controls. We also prioritized models that match common household needs, from smaller households to larger homes with multiple simultaneous hot-water demands.
Quick Comparison
For compact homes or lower-demand use, a 6.1 to 7.0 GPM unit can be enough. Mid-size households often do well with 7.9 to 8.4 GPM models, while larger homes or families with multiple bathrooms may benefit from 9.5 GPM or higher. Outdoor models can simplify venting, while indoor models may offer more placement flexibility if your home is already set up for exhaust and intake.
Key Buying Factors for Low NOx Non-Condensing Tankless Water Heaters
Fuel Type
Match the heater to your existing gas supply first. Natural gas is usually the most convenient where available, while propane is a strong option for rural properties or homes off the gas grid.
Flow Rate and BTU Output
GPM tells you how much hot water the unit can deliver, but BTU output helps explain how well it can maintain temperature as demand rises. If you routinely run showers, laundry, and a dishwasher at the same time, lean toward higher-capacity models.
Indoor Vs. Outdoor Installation
Outdoor units reduce venting complexity, but they must be suited to your climate and mounting location. Indoor models may fit better in garages, utility rooms, or basements, but they usually require more planning for venting and clearances.
Temperature Control and Smart Features
Features like precise temperature settings, WiFi, and app control are useful if you want easier adjustment and better consistency. They are not essential, but they can improve convenience, especially in busy households.
Who Should Buy Which Low Nox Non Condensing Tankless Water Heaters?
Choose a smaller-capacity unit if you live in a modest-size home, have one or two bathrooms, or want lower upfront cost. Pick a mid-range model if you need dependable whole-home performance without oversizing. Go for a higher-output unit if you have multiple bathrooms, higher fixture demand, or want more confidence during peak usage.
In short, the best low NOx non-condensing tankless water heaters balance flow, fuel, and installation requirements. Start with your home’s hot-water demand, then choose the model that fits your gas type and mounting setup.
