The best natural gas outdoor tankless water heater provides an endless supply of hot water for homes and RVs, eliminating storage tank limitations and saving valuable space. When selecting an outdoor unit, factors like BTU output, flow rate, and energy efficiency vary significantly, impacting performance. Choosing the wrong model can lead to inadequate hot water during peak demand or wasted energy, ultimately diminishing your comfort and increasing utility bills.
With numerous models on the market, navigating the options to find the perfect fit can be challenging. This roundup explores ten top-rated natural gas outdoor tankless water heaters to help you make an informed decision.
The best natural gas outdoor tankless water heater prioritizes high flow rates for multiple simultaneous uses, with models like the Rheem RTG-70XLN-3 delivering up to 7.0 GPM. Other strong contenders often feature robust BTU outputs, such as the 160,000 BTU of the Rheem RTG-70XLN-3, ensuring sufficient hot water for homes with 2-3 bathrooms needing hot water for showers and laundry.
Best Natural Gas Outdoor Tankless Water Heaters at a Glance
| Image | Product | Buy |
|---|---|---|
Best Pick 1  | Rheem RTG-70XLN-3 High Efficiency Non-Condensing Outdoor Tankless Natural Gas Water Best for: Everyday use | Check Price |
Best Pick 2  | NEW Rinnai RX199iN Condensing Smart Sense Natural Gas or Propane Best for: Smart home integration | Check Price |
Best Pick 3  | Westinghouse Natural Gas Tankless Water Heater Outdoor, 5.1 GPM 120,000 Best for: Family homes | Check Price |
Best Pick 4  | Rinnai CX199iN Condensing Smart Sense Commercial Natural Gas or Propane Best for: Businesses | Check Price |
Best Pick 5  | Rheem RTG-70DVLN-3 High Efficiency Non-Condensing Indoor Tankless Natural Gas Water Best for: Indoor installations | Check Price |
How We Picked
To determine the best natural gas outdoor tankless water heater, we prioritized build quality, real-world performance, and safety. We evaluated each unit’s GPM output and BTU rating to ensure consistent hot water delivery for multiple simultaneous uses. Durability and long-term reliability were assessed based on materials and warranty information, as seen in the extended heat exchanger coverage for some Rheem models.
Standout features like self-modulating temperature control in Mizudo units and the versatile indoor/outdoor installation of certain Rinnai models were considered. Units that did not meet the outdoor installation requirement or focus on natural gas were ruled out.
What Most Buyers Get Wrong
Outdoor Installation Requirements for Gas Heaters
When opting for an outdoor natural gas tankless water heater, it’s crucial to consider your climate. Units like the Rheem RTG-70XLN-3 and Westinghouse Natural Gas Tankless Water Heater are designed for outdoor use, but extreme cold can pose issues for any gas appliance. Ensure proper venting and consider freeze protection if you live in an area with sub-zero temperatures, as even outdoor models can suffer damage if water freezes within their components.
Always consult the manufacturer’s guidelines for specific environmental tolerances.
BTU Power and Flow Rate Pairing
The BTU (British Thermal Unit) rating of a natural gas tankless water heater dictates its heating power, while the GPM (Gallons Per Minute) indicates how much hot water it can deliver simultaneously. For homes with multiple hot water demands, like running a dishwasher and taking a shower at the same time, a higher GPM is essential. A unit like the FOGATTI Natural Gas Tankless Water Heater with 180,000 BTU and up to 8.1 GPM is designed for high demand, while the Westinghouse at 120,000 BTU and 5.1 GPM is suited for moderate use.
1. Rheem RTG-70XLN-3 High Efficiency Non-Condensing Outdoor Tankless Natural Gas Water
Best for: Ideal for 2-3 bathroom homes needing 7.0 GPM.
This Rheem RTG-70XLN-3 delivers 7.0 GPM, enabling simultaneous use of showers and laundry. Its 160,000 BTU natural gas power ensures rapid, consistent hot water for demanding households, perfect for immediate hot water needs.
With a maximum temperature of 140°F and exclusive hot-start programming, this unit minimizes cold water bursts. Its durable metal cabinet is built for outdoor wall mounting, supported by a self-diagnostic program for reliable operation.
Pros
- 7.0 GPM flow rate handles multiple hot water demands.
- 160,000 BTU heat output for fast heating.
- Hot-start programming reduces cold water delays.
- Outdoor-rated metal cabinet for durability.
Cons
- Requires installation by a qualified professional.
Homeowners with 2-3 bathrooms will appreciate this unit’s capacity for simultaneous hot water use. It’s a robust solution for ensuring consistent supply during peak household demand.
2. NEW Rinnai RX199iN Condensing Smart Sense Natural Gas or Propane
Best for: Versatile indoor/outdoor use, 11.1 GPM capacity.
The Rinnai RX199iN offers 11.1 GPM, capable of running up to 7 fixtures at once, suitable for busy households. Its Smart Sense gas control system adapts to natural gas or propane, providing flexibility with a compact, suitcase-like design.
Boasting 199,000 BTUs and a high UEF of .98, this condensing unit is highly energy efficient. It operates on 120 volts with a 98-watt draw and can maintain a maximum temperature of 140°F.
Pros
- 11.1 GPM output supports up to 7 fixtures.
- Condensing technology for high energy efficiency (UEF .98).
- Smart Sense system adapts to natural gas or propane.
- Compact size suitable for various installation spaces.
Cons
- Outdoor installation requires a separate RX-OVC vent cap.
This model is perfect for homeowners seeking a single unit for either indoor or outdoor installation, adaptable to natural gas or propane. Households needing to supply multiple high-demand fixtures will benefit from its high flow rate.
3. Westinghouse Natural Gas Tankless Water Heater Outdoor, 5.1 GPM 120,000
Best for: Consistent hot water with ±1°F accuracy.
Delivering 5.1 GPM and 120,000 BTU, the Westinghouse outdoor tankless heater provides endless hot water for showers, sinks, and appliances. Its ±1°F temperature stability ensures a consistently comfortable bathing experience.
Ideal for 2-4 fixtures running simultaneously, this unit operates on 120 volts and features CSA certification for safety. It can handle a maximum pressure of 150 PSI, providing reliable performance for everyday home use.
Pros
- 5.1 GPM flow rate for multiple appliance use.
- Precise ±1°F temperature control for comfort.
- 120,000 BTU output for ample heating.
- CSA-Certified for safety and compliance.
Cons
- Limited to 2-4 simultaneous fixtures.
This water heater is ideal for homeowners prioritizing precise temperature control and reliable endless hot water for small to medium-sized households. It’s designed for outdoor installation to meet everyday domestic hot water needs.
4. Rinnai CX199iN Condensing Smart Sense Commercial Natural Gas or Propane
Best for: Commercial-grade efficiency for lower energy costs.
The Rinnai CX199iN offers a high 11.1 GPM flow rate, suitable for commercial or high-demand residential use, supporting multiple fixtures simultaneously. Its 97% thermal efficiency rating minimizes operational costs by optimizing energy usage.
With 199,000 BTUs, this condensing model operates on 120 volts and supports a maximum temperature of 185°F, providing robust heating capabilities. It’s designed for indoor or outdoor installation with the appropriate venting.
Pros
- 11.1 GPM flow rate for high-demand applications.
- 97% thermal efficiency significantly reduces energy costs.
- High 185°F maximum temperature capability.
- Versatile indoor/outdoor installation flexibility.
Cons
- Requires a specific RX-OVC vent cap for outdoor installations.
This unit is best for businesses or large homes needing high-volume hot water with maximum energy efficiency. Its commercial-grade performance ensures reliability for demanding daily use.
5. Rheem RTG-70DVLN-3 High Efficiency Non-Condensing Indoor Tankless Natural Gas Water
Best for: Indoor installation, 7.0 GPM for 2-3 bathrooms.
Designed for indoor use, this Rheem RTG-70DVLN-3 provides 7.0 GPM, perfect for homes with 2-3 bathrooms needing concurrent hot water for showers and laundry. Its 160,000 BTU natural gas power ensures fast, reliable on-demand heating.
Featuring a compact metal cabinet, this unit operates on 120 volts and includes an integrated digital display for easy monitoring. It boasts high energy efficiency and reliable hot-start programming to minimize cold water delays.
Pros
- 7.0 GPM flow rate suitable for multiple fixtures.
- 160,000 BTU heat output for quick heating.
- Indoor design with compact cabinet.
- Integrated digital display for user convenience.
Cons
- Not designed for outdoor installation.
This model is an excellent choice for homeowners looking for an indoor tankless heater to supply hot water to 2-3 bathrooms. Its efficient performance and user-friendly display make it a practical choice for daily use.
6. Rinnai RE199eN Non-Condensing Natural Gas Tankless Water Heater, Up to
Best for: Compact design with 9.8 GPM flow rate.
The Rinnai RE199eN offers a substantial 9.8 GPM flow rate, capable of serving up to 6 fixtures simultaneously, ensuring ample hot water for busy households. Its smart design heats only when necessary, conserving energy and reducing operational costs.
This non-condensing unit features a clean internal layout for enhanced serviceability and an LED screen that provides service reminders and error codes. It operates at 199,000 BTU to provide rapid heating for immediate hot water needs.
Pros
- 9.8 GPM flow rate supports up to 6 fixtures.
- Energy conservation by heating only when needed.
- LED screen for service reminders and error codes.
- Compact design for easier installation.
Cons
- Non-condensing efficiency rating of 0.81.
This Rinnai is ideal for homes needing a reliable, high-flow water heater with smart energy-saving features. Its ease of service and clear diagnostic display make it suitable for homeowners who value convenience and efficiency.
7. Rheem RRTGH84DVLN3701171 Rheem RTGH Series 8.4 GPM 157,000 BTU 120
Best for: 8.4 GPM flow rate with exclusive hot start.
With a flow rate of 0.4 to 8.4 GPM, this Rheem RTGH Series heater quickly provides hot water for demanding households, including multiple showers and appliances. Its 157,000 BTU heat output ensures rapid and consistent performance.
This unit features exclusive hot start programming to minimize cold water bursts and an overheat film wrap for added safety. It operates on 120 volts and comes with robust manufacturer warranties including 1 year labor.
Pros
- Wide 0.4-8.4 GPM flow rate range.
- 157,000 BTU heat output for rapid heating.
- Exclusive hot start programming for comfort.
- Comprehensive manufacturer warranties included.
Cons
- Maximum temperature limited to 140°F.
This Rheem model is an excellent choice for larger homes with multiple simultaneous hot water usage points. Its high flow rate and hot start feature ensure comfort and convenience for all family members.
8. MIZUDO Natural Gas Tankless Water Heater Outdoor Installation Max 5.1
Best for: Precise ±1°F temp control for baths.
The Mizudo Gen 2 outdoor tankless water heater provides precise temperature control within ±1°F, ensuring a consistently comfortable bathing experience. Delivering up to 5.1 GPM at 120,000 BTU, it offers endless hot water for everyday use.
This unit features an upgraded temperature control system that self-modulates water temperature by integrating a gas proportional valve, water volume servo, and a built-in chip. It includes automatic anti-freezing protection and CSA certification.
Pros
- ±1°F temperature accuracy for consistent comfort.
- 5.1 GPM flow rate for typical household needs.
- 120,000 BTU output for reliable heating.
- Automatic anti-freezing protection included.
Cons
- Heat exchanger warranty is 5 years.
Homeowners seeking a reliable outdoor natural gas heater with exceptionally stable water temperatures will find this Mizudo unit ideal. It’s perfect for maintaining comfort during showers and other daily hot water tasks.
9. Rheem RTG-70XLP-3 High Efficiency Non-Condensing Outdoor Tankless Liquid Propane Water
Best for: Propane-powered, 7.0 GPM for 2-3 bathrooms.
This Rheem RTG-70XLP-3 delivers 7.0 GPM, ideal for 2-3 bathroom homes needing multiple hot water sources simultaneously. Powered by liquid propane with 160,000 BTUs, it guarantees fast, reliable hot water even during peak demand.
Designed for outdoor installation, this unit features a durable metal cabinet and supports easy wall mounting. Its compact and lightweight design, along with 1/2 gas line compatibility, simplifies installation.
Pros
- 7.0 GPM flow rate for multiple fixtures.
- 160,000 BTU heat output for rapid heating.
- Durable metal cabinet for outdoor use.
- Compact and lightweight design.
Cons
- Requires liquid propane fuel source.
This high-efficiency propane-powered unit is a great option for homes in areas without natural gas access that need to supply hot water to 2-3 bathrooms. Its outdoor design maximizes interior space.
10. FOGATTI Natural Gas Tankless Water Heater Outdoor – Max 8.1
Best for: 8.1 GPM flow rate, 3-5 outlet supply.
The FOGATTI tankless water heater provides instant hot water with up to 8.1 GPM and 180,000 BTU, capable of supplying 3-5 outlets simultaneously. This ensures continuous hot water for showers, sinks, and appliances without preheating delays.
Built for outdoor durability, this natural gas heater features a remote control panel for convenient indoor operation and a bottom-mounted fan. It offers energy saving and high efficiency, supported by a 2 to 5-year warranty.
Pros
- 8.1 GPM flow rate for extensive use.
- 180,000 BTU output for strong heating.
- Supplies hot water to 3-5 outlets simultaneously.
- Outdoor-specific durable design.
Cons
- Requires a separate remote control panel for indoor operation.
This FOGATTI unit is perfect for larger homes or properties with multiple hot water demands that require simultaneous use from 3-5 points. Its robust outdoor design ensures lasting performance.
Condensing vs. Non-Condensing: The Real Outdoor Heater Choice
The most critical differentiator for a best natural gas outdoor tankless water heater isn’t flow rate or BTUs, but its condensing versus non-condensing design, a distinction that directly impacts efficiency and installation cost.
Non-condensing units, like the Rheem RTG-70XLN-3 and the Rheem RTG-70XLP-3 (which interestingly runs on propane), typically exhaust at higher temperatures. This means they can utilize standard PVC venting, which is considerably less expensive and simpler to install than the specialized stainless steel venting required for condensing models. The Westinghouse Natural Gas Tankless Water Heater Outdoor, 5.1 GPM offers a straightforward, non-condensing approach suitable for basic outdoor needs.
Condensing units, exemplified by the Rinnai RX199iN Condensing Smart Sense and the Rinnai CX199iN Condensing Smart Sense, reclaim heat from exhaust gases, achieving higher energy efficiency ratings. This efficiency translates to lower ongoing fuel costs. However, this heat recovery process cools the exhaust gases to a point where water vapor condenses, necessitating corrosion-resistant, Type 316L stainless steel venting due to the acidic nature of the condensate.
This type of venting significantly increases the upfront installation expense. The Rinnai RE199eN, while non-condensing, still boasts an improved design for energy conservation.
For many outdoor applications where simplicity and initial cost are paramount, a robust non-condensing unit like the Rheem RTGH Series 8.4 GPM offers excellent performance without the added complexity and expense of condensing technology. However, if long-term operating costs are a significant concern and the budget allows for the specialized venting, condensing models from Rinnai or Rheem provide superior energy recovery. The FOGATTI Natural Gas Tankless Water Heater Outdoor, 8.1 GPM, is a high-flow non-condensing option that prioritizes immediate hot water delivery.
Ultimately, users prioritizing a straightforward, budget-friendly outdoor installation will find excellent value in non-condensing units, while those focused on long-term operational savings and willing to invest more upfront will benefit from the efficiency of a condensing model like the Rinnai RX199iN Condensing Smart Sense.
What to Look for in a Natural Gas Outdoor Tankless Water Heater
Flow rate gpm
Prioritize a flow rate of at least 9.5 GPM for homes with multiple simultaneous hot water needs, such as running two showers and a dishwasher. Lower GPM units, typically below 7 GPM, will struggle to maintain temperature under such demand, leading to lukewarm water. For high-demand scenarios, look for models explicitly rated for 10 GPM or higher.
This ensures ample hot water, even when multiple fixtures are in use, directly impacting your comfort and heating efficiency by preventing the unit from operating at its maximum, less efficient output to keep up. Choose a 9.5 GPM or higher unit for assured performance.
Energy factor ef
When selecting a natural gas tankless water heater, an Energy Factor (EF) of 0.90 or higher is the benchmark for optimal efficiency. While ratings can vary, units with EFs between 0.80 and 0.85 represent a significant step down in energy conservation. A higher EF indicates less wasted energy during operation, translating directly to lower monthly natural gas bills.
Always compare the EF ratings of different models; a difference of just 0.05 can result in substantial long-term savings. For the most cost-effective operation, select a unit with an EF of 0.90 or above.
Temperature control and settings
For precise water temperature management, digital controls offering a wide, adjustable range are superior to basic manual knobs. Seek models that allow temperature adjustments in single-degree increments, ideally from 90°F to 140°F, providing granular control for various needs, from handwashing to dishwashing. Preset modes, while convenient, should ideally supplement, not replace, detailed digital adjustments.
This digital precision prevents excessive heating and potential scalding, ensuring comfort and safety. Opt for a heater with advanced digital controls and a broad temperature range for maximum versatility.
Venting and installation requirements
Proper venting is crucial for safety and performance. For outdoor natural gas units, direct vent systems are strongly recommended as they are sealed combustion and do not draw combustion air from your home, ensuring your safety. Verify that any chosen model adheres to all manufacturer clearances, typically 12-18 inches from combustible materials and specific distances from windows and doors.
Ensure your existing gas line is at least 0.75 inches in diameter; undersized lines will restrict gas flow and reduce heating capacity. Select a direct-vent unit with clear, achievable clearance requirements for safe and effective installation.
Which Should You Choose?
- If you have a medium-sized home with 2-3 bathrooms and use hot water simultaneously, look for a unit with at least 7.0 GPM.
- If you need hot water for a single shower or sink use, a unit around 5.1 GPM might be sufficient.
- If you require maximum hot water flow for large homes or multiple simultaneous uses, consider models offering 8.1 GPM or higher.
- If installation location flexibility is a priority, opt for a model that is specifically designed for outdoor installation or offers indoor/outdoor versatility.
Quick Best Natural Gas Outdoor Tankless Water Heater Buying Checklist
- Confirm Required GPM: Ensure the heater’s flow rate meets your household’s peak demand, especially for simultaneous use.
- Check Energy Factor (EF): Higher EF ratings indicate greater energy efficiency and potential cost savings over time.
- Evaluate Temperature Control: Look for precise digital controls for consistent water temperatures tailored to your needs.
- Understand Venting Needs: Verify the venting system compatibility and required clearances for your installation location.
- Consider Material Durability: Opt for models with robust construction, especially for outdoor units exposed to the elements.
- Review Manufacturer Warranty: Assess the warranty period and coverage for peace of mind.
Frequently Asked Questions
What Gpm Is Needed For A Natural Gas Outdoor Tankless Water Heater?
The required GPM for a natural gas outdoor tankless water heater depends on your simultaneous usage. For average households, 5-7 GPM is often sufficient, but high-demand homes with multiple showers may need 8 GPM or more.
How Does Energy Factor (Ef) Impact My Bill For This Type Of Heater?
A higher Energy Factor (EF) on your natural gas outdoor tankless water heater means it’s more efficient at converting gas into hot water. This directly translates to lower fuel consumption and reduced monthly utility bills.
What Are Common Venting Options For Outdoor Tankless Units?
Natural gas outdoor tankless water heaters commonly use direct venting or power venting. Direct venting draws outside air for combustion and exhausts through a wall, while power venting uses a fan to expel exhaust gases.
Can I Adjust The Temperature On An Outdoor Tankless Unit?
Yes, most natural gas outdoor tankless water heaters feature adjustable temperature settings, often via a digital interface. This allows you to precisely control your hot water output for comfort and efficiency.
What Maintenance Is Typically Required For These Heaters?
Regular maintenance for a natural gas outdoor tankless water heater includes annual flushing to prevent mineral buildup and checking vent connections. Periodic inspection by a qualified technician is also recommended.
Final Words
Choosing the best natural gas outdoor tankless water heater offers a continuous supply of hot water with excellent energy efficiency. These units provide reliable performance and space-saving benefits for your outdoor living areas. Invest in a model that suits your flow rate needs and enjoy enhanced convenience and comfort.