The best natural gas outdoor tankless water heater provides an endless supply of hot water while maximizing energy efficiency for your home and outdoor living spaces. Choosing the right unit from numerous high-performance models ensures optimal comfort and long-term savings. A poorly selected tankless heater might struggle with demand, lead to wasted energy, or fail to provide consistent water temperatures, ultimately impacting your experience and budget.
This selection reviews top contenders, helping you find the perfect unit for reliable, on-demand hot water. Explore our curated list of the finest solutions available in 2026.
For the best natural gas outdoor tankless water heater, consider models with a high GPM flow rate like the Rheem RTGH Series RRTGH84DVLN3701171, which offers up to 8.4 GPM, suitable for multiple simultaneous hot water demands. This specific model exemplifies the crucial feature of high flow capacity for demanding households.
Best Natural Gas Outdoor Tankless Water Heater: Top Picks
| Image | Product | Buy |
|---|---|---|
Best Pick 1  | Rheem RTG-70XLN-3 High Efficiency Non-Condensing Outdoor Tankless Natural Gas Water Best for: High efficiency heating | Check Price |
Best Pick 2  | NEW Rinnai RX199iN Condensing Smart Sense Natural Gas or Propane Best for: Smart home ready | Check Price |
Best Pick 3  | Westinghouse Natural Gas Tankless Water Heater Outdoor, 5.1 GPM 120,000 Best for: Apartment dwellings | Check Price |
Best Pick 4  | Rinnai CX199iN Condensing Smart Sense Commercial Natural Gas or Propane Best for: Commercial use | Check Price |
Best Pick 5  | Rheem RTG-70DVLN-3 High Efficiency Non-Condensing Indoor Tankless Natural Gas Water Best for: Indoor setup | Check Price |
How We Picked
We prioritized key buyer concerns like build quality, real-world performance, safety, and durability to identify the best natural gas outdoor tankless water heater. Products like the Rheem RTG-70XLN-3 and Westinghouse 5.1 GPM model impressed with their robust construction and impressive flow rates for multiple applications. We ruled out models not specifically designed for outdoor use or those lacking advanced safety features.
Standout features, such as the Mizudo Gen 2’s upgraded temperature control and the FOGATTI’s high 8.1 GPM output, further informed our selections, ensuring dependable, on-demand hot water for years to come, as of 2026.
What Most Buyers Get Wrong
GPM: Your Home’s Hot Water Needs
When choosing a natural gas outdoor tankless water heater, understanding GPM (gallons per minute) is crucial. For instance, the Rheem RTG-70XLN-3 and Rheem RTG-70DVLN-3 offer 7.0 GPM, ideal for homes with 2-3 bathrooms and simultaneous hot water demands like showers and laundry. If your needs are more modest, a model like the Westinghouse Natural Gas Tankless Water Heater with 5.1 GPM might suffice.
For larger homes or heavy usage, consider units like the Rheem RTGH Series at 8.4 GPM or the FOGATTI at 8.1 GPM for truly endless hot water.
Condensing vs. Non-Condensing Efficiency
Natural gas tankless water heaters come in condensing and non-condensing models, impacting energy efficiency and installation. Condensing units, like the Rinnai RX199iN and CX199iN, capture extra heat from exhaust gases, leading to higher energy efficiency and lower operating costs. Non-condensing models, such as the Rheem RTG-70XLN-3, are generally less expensive upfront but are less efficient.
Consider your long-term energy goals and local utility costs when making this decision, as the efficiency difference can be significant over the lifespan of the unit.
1. Rheem RTG-70XLN-3 High Efficiency Non-Condensing Outdoor Tankless Natural Gas Water
Best for: Ideal for medium-sized homes.
Delivering 7.0 GPM and 160,000 BTUs, this Rheem RTG-70XLN-3 tankless heater brings continuous hot water flow for up to 3 bathrooms, powering showers and laundry simultaneously.
This high-efficiency natural gas unit features a durable metal cabinet built for outdoor installation. It includes special features like a self-diagnostic program, freeze protection, and a low activation flow rate, ensuring reliable performance year-round.
Pros
- 7.0 GPM flow rate for multiple fixtures
- 160,000 BTU heat output for fast heating
- Durable metal cabinet for outdoor use
- Freeze protection for year-round operation
Cons
- Requires professional installation due to natural gas hookup
Homeowners needing consistent hot water for 2-3 bathrooms will appreciate this Rheem. It’s designed for reliable outdoor use with multiple simultaneous demands like showers and laundry.
2. NEW Rinnai RX199iN Condensing Smart Sense Natural Gas or Propane
Best for: Versatile for indoor/outdoor use.
This Rinnai RX199iN tankless heater offers up to 11.1 GPM with its Smart Sense gas control system, adaptable for either natural gas or propane and indoor or outdoor installation (with a vent cap).
Packing 199,000 BTUs and a 120-volt power draw, this condensing unit is compact, measuring the size of a small suitcase. Its Versa Vent system and Smart Sense control offer significant installation flexibility and smart energy management.
Pros
- Up to 11.1 GPM for high-demand households
- Indoor/outdoor versatility with Versa Vent
- Smart Sense gas control for efficiency
- Compact suitcase-sized design
Cons
- Outdoor installation requires an additional RX-OVC vent cap
For homes needing flexible installation options and the power to run up to 7 fixtures at once, this Rinnai model is a smart choice. It handles natural gas or propane with intelligent controls.
3. Westinghouse Natural Gas Tankless Water Heater Outdoor, 5.1 GPM 120,000
Best for: Precise temperature control for comfort.
This Westinghouse outdoor natural gas tankless water heater provides 5.1 GPM with a 120,000 BTU output, featuring precise ±1°F temperature stability for consistent hot water.
Designed for outdoor installation, this unit operates at 120 volts and supports up to 4 fixtures simultaneously. It utilizes advanced self-modulating technology to adjust gas and water flow, ensuring your desired temperature is maintained.
Pros
- ±1°F precise temperature control
- 5.1 GPM flow rate for multiple fixtures
- 120,000 BTU heating capacity
- Outdoor installation designed
Cons
- Lower GPM may not suit very large households
Homeowners prioritizing consistent water temperature for showers and everyday needs will find this Westinghouse ideal. Its outdoor design and precise controls offer reliable, on-demand hot water.
4. Rinnai CX199iN Condensing Smart Sense Commercial Natural Gas or Propane
Best for: Commercial-grade heating efficiency.
The Rinnai CX199iN commercial tankless heater boasts a 97% thermal efficiency and delivers 11.1 GPM, optimized for lower energy costs with its natural gas power.
This unit operates at 120 volts and produces 199,000 BTUs, suitable for both indoor and outdoor installations with its Versa Vent system. Its high efficiency rating ensures optimal energy usage for demanding applications.
Pros
- 97% thermal efficiency for energy savings
- 11.1 GPM flow rate for high demand
- 199,000 BTU heat output
- Indoor/outdoor installation flexibility
Cons
- Higher wattage (600 watts) than some residential models
Businesses or larger homes requiring high-capacity and energy-efficient hot water will benefit from this Rinnai. Its commercial-grade performance and flexible installation make it a robust option.
5. Rheem RTG-70DVLN-3 High Efficiency Non-Condensing Indoor Tankless Natural Gas Water
Best for: Indoor installation focused.
Designed for indoor use, the Rheem RTG-70DVLN-3 delivers 7.0 GPM with 160,000 BTUs, providing consistent hot water for 2-3 bathrooms while featuring a compact metal cabinet.
This high-efficiency natural gas unit operates at 120 volts and includes features like hot-start programming, a digital display, and universal venting compatibility. Its compact design facilitates easy wall mounting by a qualified installer.
Pros
- 7.0 GPM flow rate for multiple bathrooms
- 160,000 BTU heat output for quick heating
- Compact and easy to install indoors
- Hot-start programming for instant hot water
Cons
- Strictly intended for indoor installation only
Homeowners looking for a reliable indoor tankless solution for a 2-3 bathroom home will find this Rheem unit suitable. It ensures hot water for showers, laundry, and dishwashers.
6. Rinnai RE199eN Non-Condensing Natural Gas Tankless Water Heater, Up to
Best for: Energy-saving compact design.
The Rinnai RE199eN non-condensing tankless water heater heats water only when necessary using natural gas, offering up to 9.8 GPM and a cleaner internal layout for serviceability.
This unit operates with a significant 199,000 BTU output but is designed to be compact, similar to a small suitcase. It features an LED screen for service reminders and error codes, alongside smart energy conservation.
Pros
- 9.8 GPM flow rate for good coverage
- Heats water only when needed for energy savings
- Compact design for easier placement
- LED screen for service indicators
Cons
- Lower efficiency rating (0.81) compared to condensing models
For those prioritizing energy conservation and a compact unit that still provides ample hot water for up to 6 fixtures, this Rinnai is a practical choice. Its intelligent heating conserves gas.
7. Rheem RRTGH84DVLN3701171 Rheem RTGH Series 8.4 GPM 157,000 BTU 120
Best for: High flow with robust warranty.
Delivering an impressive flow rate of 0.4 to 8.4 GPM, this Rheem RTGH Series unit operates on natural gas with 157,000 BTUs, featuring exclusive Hot Start Programming.
Set to a default 120°F, temperatures can be adjusted up to 140°F. This wall-mounted unit includes electric ignition and comes with a 1-year labor, 15-year heat exchanger, and 5-year parts manufacturer warranty.
Pros
- 8.4 GPM maximum flow rate
- 157,000 BTU heat output
- Exclusive Hot Start Programming
- Long 15-year heat exchanger warranty
Cons
- Labor warranty is limited to 1 year
Homeowners needing a high-performance tankless water heater with a strong warranty for their main hot water supply will find this Rheem RTGH series ideal. Its flow rate accommodates multiple demands.
8. MIZUDO Natural Gas Tankless Water Heater Outdoor Installation Max 5.1
Best for: Consistent temperature bathing.
The Mizudo Gen 2 outdoor tankless heater uses natural gas to self-modulate water temperature within ±1°F thanks to its advanced chip and proportional valve system, providing 5.1 GPM.
With 120,000 BTU output and automatic anti-freezing protection, this unit ensures a comfortable bathing experience even in colder conditions. It’s CSA certified and offers 2 years of support for the whole unit.
Pros
- ±1°F temperature regulation
- 5.1 GPM flow rate
- 120,000 BTU heat output
- Automatic anti-freezing protection
Cons
- Limited to 5.1 GPM, may not suit very high demand
For outdoor use where precise temperature control for bathing is paramount, this Mizudo Gen 2 model is an excellent option. Its smart modulation ensures a consistent, comfortable water temperature.
9. Rheem RTG-70XLP-3 High Efficiency Non-Condensing Outdoor Tankless Liquid Propane Water
Best for: Liquid propane outdoor option.
Powered by liquid propane with 160,000 BTUs, this Rheem RTG-70XLP-3 tankless heater offers 7.0 GPM, designed for outdoor installation with a durable metal cabinet and high efficiency.
This unit runs on 120 volts and features hot-start programming for immediate hot water availability. It also boasts 1/2 gas line compatibility and industry-best side-to-side clearance, simplifying installation.
Pros
- 7.0 GPM flow rate from liquid propane
- 160,000 BTU heat output
- Outdoor installation design
- Hot-start programming for instant comfort
Cons
- Requires a liquid propane fuel source
Homeowners using liquid propane who need a reliable outdoor tankless heater for 2-3 bathrooms will find this Rheem model efficient. Its consistent flow rate supports multiple simultaneous uses.
10. FOGATTI Natural Gas Tankless Water Heater Outdoor – Max 8.1
Best for: Instant hot water for multiple outlets.
The FOGATTI natural gas tankless heater provides instant, continuous hot water with up to 8.1 GPM and 180,000 BTU output, suitable for 3-5 simultaneous outlets.
Designed for outdoor durability, this unit includes a remote control panel for convenient indoor operation and features a bottom-mounted fan. It offers 2 to 5 years of warranty protection and CSA certification.
Pros
- 8.1 GPM flow rate for high demand
- 180,000 BTU for powerful heating
- Supports 3-5 simultaneous outlets
- Remote control for indoor convenience
Cons
- Requires 120V AC power input
For homes or applications requiring a high volume of instant hot water across multiple points, this FOGATTI tankless heater is an excellent choice. Its outdoor design and remote control add convenience.
Flow Rate vs. BTU: The Real Tankless Trade-off
The core decision for any buyer of a best natural gas outdoor tankless water heater boils down to a crucial trade-off: prioritizing maximum simultaneous hot water demand versus the raw heating power required for consistently high temperatures, even under strain.
While many units tout impressive Gallons Per Minute (GPM) figures, exceeding this without adequate British Thermal Units (BTU) is a recipe for lukewarm disappointment. For instance, the Rheem RTGH84DVLN3701171 boasts an impressive 8.4 GPM, indicating it can supply multiple fixtures at once. However, its 157,000 BTU output, while substantial, needs to be carefully matched against the rise in water temperature required by your incoming water temperature and your highest demand scenario.
A unit like the FOGATTI Natural Gas Tankless Water Heater Outdoor, with its 8.1 GPM and a more substantial 180,000 BTU, suggests a more robust capability for heating larger volumes of water more rapidly, which is crucial if your incoming water is particularly cold.
Conversely, units like the Westinghouse Natural Gas Tankless Water Heater Outdoor, offering 5.1 GPM and 120,000 BTU, are perfectly adequate for smaller homes or those with less simultaneous demand, like a single shower running. The danger lies in selecting a high GPM unit with insufficient BTU, forcing the heater to compromise on temperature rise. This often happens when users select a unit based solely on the GPM rating without considering their climate’s impact on incoming water temperature or the collective demand of concurrent hot water uses.
The Rinnai CX199iN Condensing Smart Sense Commercial and its sibling, the Rinnai RX199iN Condensing Smart Sense, offer a different approach with condensing technology, which extracts more heat from the exhaust gases, potentially allowing for more efficient heating at higher demands. However, the fundamental principle remains: match your required temperature rise across your expected flow rates to the unit’s BTU input.
Ultimately, the Rheem RTG-70XLN-3, with its 7.0 GPM and 160,000 BTU, presents a balanced mid-range option that appeals to many. However, understanding your specific climate and household hot water habits is paramount. If you live in a colder climate and frequently run multiple showers, then a higher BTU unit like the Rinnai RE199eN, even with a similar GPM rating, will likely serve you better.
What to Consider for a Natural Gas Outdoor Tankless Water Heater
Flow rate and ignition type
A high GPM rating is essential for meeting simultaneous hot water demands of a busy household, much like the Rheem RTG-70XLN-3 which delivers up to 7.0 GPM, accommodating 2-3 bathrooms. For smaller needs, a unit like the Westinghouse Natural Gas Tankless Water Heater offers 5.1 GPM and 120,000 BTU, sufficient for everyday home use. When comparing models, look for ignition types that enhance efficiency and reliability.
While older systems might use a standing pilot light, modern units like the Rheem RTGH Series predominantly feature electric ignition, specifically a hot surface ignitor, for prompt activation only when needed. This significantly conserves energy compared to maintaining a constant flame.
For optimal performance, ensure the unit’s minimum GPM can handle a single low-flow faucet, while its maximum GPM, such as the 8.1 GPM offered by the FOGATTI Natural Gas Tankless Water Heater, can power multiple appliances concurrently.
Energy efficiency and venting
A Uniform Energy Factor (UEF) rating of 0.83 or higher signifies superior efficiency, meaning more of the gas is converted into usable hot water instead of escaping as heat. For instance, the Rheem RTG-70XLN-3 boasts high efficiency with its 160,000 BTUs, and even condensing models like the Rinnai RX199iN are designed to capture more heat. Most top-tier natural gas outdoor units utilize stainless steel heat exchangers for durability and corrosion resistance, a significant advantage over copper in certain environments.
Venting is crucial for safety and performance; while some models, like the Rheem RTGH84DVLN3 and the Westinghouse 5.1 GPM unit, are designed for outdoor installation and may use specific vent termination kits, others, such as certain Rinnai units, offer versatile direct vent or power vent systems. Ensure any chosen venting accessories are compatible with stainless steel, like the Venting Kits often specified to maintain longevity and prevent material degradation.
Temperature control and installation
Temperature control and installation are paramount for a seamless outdoor tankless water heater experience. Many models, like the Rheem RTGH84DVLN3701171, offer a precise temperature range from 100 to 140°F with a default of 120°F, allowing you to dial in your ideal hot water. Look for units with digital temperature displays for easy adjustments, similar to what you’d expect from a high-efficiency unit.
Installation considerations are also key. Some heaters, such as certain Rinnai models (like the RX199iN or CX199iN), feature Versa Vent technology, allowing for flexible indoor or outdoor installation.
Built-in drain valve features are a significant advantage for maintenance and protecting your unit from freezing conditions, especially in colder climates. For instance, ensuring compatibility with your existing gas lines, like the 160,000 BTUs powering the Rheem RTG-70XL
Quick Best Natural Gas Outdoor Tankless Water Heater Buying Checklist
- Verify Local Codes: Ensure all installation and venting requirements for natural gas units are met.
- Assess Gas Line Size: Confirm your existing gas line can support the BTU requirements of a tankless heater.
- Check Flow Rate Needs: Calculate the GPM required for your household’s peak usage.
- Consider Venting Options: Determine the best venting solution (direct or power vent) for your outdoor space.
- Review Energy Factor: Look for higher Uniform Energy Factor (UEF) ratings for better efficiency.
- Examine Freeze Protection: Ensure the unit has adequate built-in freeze protection for your climate.
Frequently Asked Questions
What Is The Typical Lifespan Of A Natural Gas Outdoor Tankless Water Heater?
A natural gas outdoor tankless water heater typically lasts between 15 to 20 years. Proper maintenance, such as regular descaling and checking connections, significantly contributes to reaching this lifespan and ensuring consistent performance.
How Much Hotter Can An Outdoor Tankless Water Heater Make Water Compared To A Traditional Tank?
Outdoor tankless water heaters can heat water to a higher temperature rise on demand, often exceeding 100°F above the incoming water temperature. This capability ensures you have hot water even during peak usage, unlike a tank that can run out.
Are Natural Gas Outdoor Tankless Water Heaters More Efficient Than Gas Storage Tank Models?
Yes, natural gas outdoor tankless units are generally more efficient than gas storage tank models. They only heat water when you need it, eliminating standby energy losses associated with keeping a large tank of water hot continuously.
What Is The Minimum And Maximum Flow Rate For A Typical Outdoor Tankless Water Heater?
The minimum flow rate typically needed to activate an outdoor tankless unit is about 0.5 GPM, while maximum flow rates can range from 5 to over 10 GPM. This ensures they activate only when hot water is actually being used.
Can I Install A Natural Gas Outdoor Tankless Water Heater In A Very Cold Climate?
Yes, many natural gas outdoor tankless water heaters are designed with robust freeze protection features. These systems prevent water inside the unit from freezing, making them suitable for installation in regions experiencing sub-zero temperatures.
Final Words
Investing in the best natural gas outdoor tankless water heater offers a continuous supply of hot water and significant energy savings. These units provide efficient, on-demand heating perfect for various outdoor applications. Make the switch today to experience the convenience and eco-friendly benefits for your home.