The best natural gas outdoor tankless water heater provides a continuous supply of hot water for your home, ideal for families and busy households. Selecting the right unit involves understanding key differences in flow rate, energy efficiency, and venting requirements, as a mismatch can lead to lukewarm water or wasted energy. Features like freeze protection and digital temperature control further enhance usability and performance.
Investing wisely ensures years of reliable hot water without the limitations of traditional tanks. To help you make an informed choice, explore our curated list of top-performing natural gas outdoor tankless water heaters.
For the best natural gas outdoor tankless water heater, consider models like the Rheem RTG-70XLN-3, which offers up to 7.0 GPM and 160,000 BTUs, suitable for 2-3 bathroom homes needing continuous hot water. Other high-performing options include the Westinghouse Natural Gas Tankless Water Heater with 5.1 GPM and 120,000 BTU, and the MIZUDO Gen 2, featuring upgraded temperature control for consistent heating.
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: Higher home usage | 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: Moderate home use | Check Price |
Best Pick 4  | Rinnai CX199iN Condensing Smart Sense Commercial Natural Gas or Propane Best for: Commercial needs | Check Price |
Best Pick 5  | Rheem RTG-70DVLN-3 High Efficiency Non-Condensing Indoor Tankless Natural Gas Water Best for: Indoor installation | Check Price |
How We Picked
We meticulously evaluated numerous options to identify the best natural gas outdoor tankless water heater. Our selection prioritized robust build quality and proven, real-world performance. Safety features were paramount, ensuring reliable operation for everyday use.
Durability was a key consideration, favoring models designed for longevity. Standout features like advanced temperature control and high GPM flow rates were weighed to offer superior hot water delivery.
We ruled out units that did not meet our stringent criteria for dependable outdoor installation and consistent heating for multiple applications, ensuring a high-value purchase for 2026.
What Most Buyers Get Wrong
Outdoor Natural Gas: Venting and Weatherproofing
When choosing an outdoor natural gas tankless water heater, especially in climates with harsh weather, consider its construction. Units designed for outdoor use, like the Rheem RTG-70XLN-3 or the Westinghouse Natural Gas Tankless Water Heater, need to withstand rain, snow, and extreme temperatures. Look for corrosion-resistant materials and proper sealing to prevent internal damage.
Ensure the unit is installed in a location protected from direct wind and excessive moisture, typically under an eave or with a dedicated outdoor vent cover, to maximize its lifespan and performance.
Matching Flow Rate to Your Home’s Needs
The GPM or gallons per minute is a critical spec for natural gas tankless water heaters. A higher GPM means more hot water can be delivered simultaneously. For a 2-3 bathroom home with multiple simultaneous uses like showers and laundry, a unit with 7.0 GPM or higher, such as the Rheem RTG-70XLN-3 or Rheem RRTGH84DVLN3701171, is recommended.
For smaller homes or fewer simultaneous demands, models like the Westinghouse Natural Gas Tankless Water Heater or MIZUDO Natural Gas Tankless Water Heater with 5.1 GPM might suffice. Over-sizing can lead to wasted energy, while under-sizing leaves you short on hot water.
1. Rheem RTG-70XLN-3 High Efficiency Non-Condensing Outdoor Tankless Natural Gas Water
Best for: Up to 7.0 GPM for 2-3 baths.
Delivering up to 7.0 GPM, this Rheem RTG-70XLN-3 ensures ample hot water for homes with 2-3 bathrooms, allowing simultaneous use of showers and laundry. Its 160,000 BTU natural gas power provides rapid, reliable heating.
This high-efficiency, non-condensing unit features a durable metal cabinet designed for outdoor wall mounting. It boasts a low activation flow rate and freeze protection, ensuring consistent performance in various conditions. The unit includes a digital display and self-diagnostic programming for ease of use and maintenance.
Pros
- 7.0 GPM flow rate for multiple fixtures
- 160,000 BTU heat output for fast heating
- Outdoor installation saves indoor space
- Freeze protection for year-round use
Cons
- Hot-start programming is not a standard feature, requiring a brief wait for initial hot water.
This Rheem model is ideal for homeowners needing a reliable, high-flow outdoor tankless water heater for moderate-sized households. It’s a solid choice for general residential hot water demands.
2. NEW Rinnai RX199iN Condensing Smart Sense Natural Gas or Propane
Best for: Indoor/Outdoor, Propane or NG, 11.1 GPM.
This Rinnai RX199iN offers remarkable versatility, suitable for both indoor and outdoor installation and compatible with natural gas or propane, allowing placement flexibility. Its compact, suitcase-like size belies its capacity for up to 11.1 GPM.
Featuring Smart Sense gas control and a Versa Vent system, it achieves a high efficiency of UEF .98. The unit operates efficiently with 98 watts and 120 volts, producing 199,000 BTU to maintain a maximum temperature of 140°F. It also supports smart home compatibility.
Pros
- Indoor or outdoor installation flexibility
- Propane or natural gas compatibility
- 11.1 GPM for up to 7 fixtures
- Compact, suitcase-sized design
Cons
- Outdoor installation requires the separate RX-OVC vent cap.
This Rinnai unit is perfect for homeowners seeking a flexible tankless water heater that can adapt to various installation scenarios. Its high flow rate makes it suitable for larger homes or demanding hot water needs.
3. Westinghouse Natural Gas Tankless Water Heater Outdoor, 5.1 GPM 120,000
Best for: 5.1 GPM with ±1°F temp control.
Designed for outdoor natural gas use, this Westinghouse tankless water heater provides 5.1 GPM with exceptional ±1°F temperature stability, offering consistent hot water for showers and appliances. It delivers 120,000 BTU for on-demand heating.
This unit comfortably supports 2-4 fixtures simultaneously, ensuring no interruptions for everyday home use. Its advanced self-modulating technology precisely adjusts gas and water flow. The heater supports 150 PSI maximum pressure and comes with 2-5 years of after-sale support.
Pros
- Precise ±1°F temperature control
- 5.1 GPM for 2-4 fixtures
- 120,000 BTU heat output
- Outdoor installation design
Cons
- The 5.1 GPM flow rate may be insufficient for homes with more than 4 fixtures running simultaneously.
This Westinghouse model is an excellent choice for homeowners prioritizing precise temperature control and consistent hot water for moderate fixture usage. Its outdoor design is ideal for garages or outbuildings.
4. Rinnai CX199iN Condensing Smart Sense Commercial Natural Gas or Propane
Best for: Commercial-grade, 11.1 GPM, 96% efficient.
The Rinnai CX199iN is a commercial-grade condensing tankless water heater offering 11.1 GPM and an impressive 96% efficiency for reduced operational costs. Its design prioritizes super high efficiency while providing abundant hot water.
This unit can be installed indoors or outdoors with the appropriate Venturi system, powered by natural gas. It delivers 199,000 BTU to reach a maximum temperature of 185°F, suitable for demanding applications. The water heater supports smart home connectivity and a maximum pressure of 150 PSI.
Pros
- 11.1 GPM for high demand
- 96% energy efficiency
- Commercial-grade performance
- Smart home compatible
Cons
- The 600 watts power consumption is higher than many residential models.
This Rinnai commercial model is best suited for businesses or large homes with exceptionally high hot water demands. Its efficiency and high flow rate make it a powerful and cost-effective solution.
5. Rheem RTG-70DVLN-3 High Efficiency Non-Condensing Indoor Tankless Natural Gas Water
Best for: Indoor use, 7.0 GPM, Hot-Start.
The Rheem RTG-70DVLN-3 is an indoor-only, high-efficiency tankless gas water heater providing up to 7.0 GPM, perfectly suited for 2-3 bathroom homes. Its 160,000 BTU output ensures fast, reliable hot water during peak demand.
This unit features a compact metal cabinet and supports easy wall mounting for indoor installations. It boasts hot-start programming for quicker hot water delivery, an integrated digital display, and universal venting compatibility. It uses 132 watts and 120 volts, connecting to a 1/2 gas line.
Pros
- 7.0 GPM flow rate
- Indoor installation
- Hot-start programming
- Compact metal cabinet
Cons
- This model is exclusively for indoor installation; it cannot be used outdoors.
This Rheem model is an ideal pick for homeowners looking to replace an existing indoor water heater in a 2-3 bathroom home. Its hot-start feature adds convenience for daily use.
6. Rinnai RE199eN Non-Condensing Natural Gas Tankless Water Heater, Up to
Best for: 7.6 GPM, non-condensing, space-saving.
This Rinnai RE199eN is a non-condensing tankless water heater designed for outdoor use, delivering up to 7.6 GPM from a compact, suitcase-sized unit. Its smart design heats water only when necessary, conserving energy.
With a heat output of 199,000 BTU and a flow rate of 9.8 GPM, it can serve up to 6 fixtures simultaneously. The heater features an LED screen that provides service reminders and error codes, enhancing ease of maintenance. It operates at 140°F maximum temperature.
Pros
- 7.6 GPM flow rate
- Compact, space-saving design
- Energy-conserving heating
- LED service indicators
Cons
- The efficiency rating of 0.81 is lower than condensing models.
This Rinnai unit is a practical choice for homes needing reliable outdoor tankless hot water for up to 6 fixtures. Its energy-saving design and clear service indicators add value.
7. Rheem RRTGH84DVLN3701171 Rheem RTGH Series 8.4 GPM 157,000 BTU 120
Best for: 8.4 GPM flow rate, 157,000 BTU.
The Rheem RTGH Series offers an impressive flow rate of 0.4 to 8.4 GPM, ideal for high-demand households needing abundant hot water. With an output of 157,000 BTU and electric ignition, it ensures fast, efficient heating for multiple fixtures.
This unit is covered by a 1-year labor, 15-year heat exchanger, and 5-year parts manufacturer warranty, providing peace of mind. It features exclusive hot start programming and overheat film wrap for enhanced safety and performance. The default temperature setting is 120°F, with a range of 100-140°F.
Pros
- 8.4 GPM maximum flow rate
- 157,000 BTU heat output
- Electric ignition for reliability
- Comprehensive manufacturer warranty
Cons
- The unit has a fixed width of 17-11/16-in, which may affect installation space considerations.
This Rheem RTGH Series model is recommended for large families or homes with multiple bathrooms and high simultaneous hot water needs. Its robust flow rate ensures everyone gets hot water when they need it.
8. MIZUDO Natural Gas Tankless Water Heater Outdoor Installation Max 5.1
Best for: 5.1 GPM with ±1°F temp control, outdoor.
The MIZUDO Gen 2 outdoor tankless water heater delivers 5.1 GPM with precise ±1°F temperature control, ensuring a consistent and comfortable bathing experience. Its 120,000 BTU output provides endless hot water for everyday use.
Featuring an upgraded temperature control system with a gas proportional valve and water volume servo, it maintains stable temperatures. This unit also includes automatic anti-freezing protection and CSA certification for quality and safety. It operates at 120 volts and 43 watts.
Pros
- Precise ±1°F temperature stability
- 5.1 GPM flow rate
- Automatic anti-freezing protection
- CSA Certified
Cons
- While rated for 5.1 GPM, it may not be sufficient for more than 2-3 simultaneous fixtures in colder climates.
This Mizudo tankless water heater is a great selection for outdoor installations where consistent water temperature is a priority. It’s well-suited for modest hot water demands in cabins or secondary residences.
9. Rheem RTG-70XLP-3 High Efficiency Non-Condensing Outdoor Tankless Liquid Propane Water
Best for: Liquid Propane, 7.0 GPM, Outdoor.
This Rheem RTG-70XLP-3 is an outdoor tankless water heater powered by liquid propane, delivering up to 7.0 GPM for 2-3 bathroom homes. Its 180,000 BTU output guarantees fast and reliable hot water, even during peak demand.
Featuring a durable metal cabinet and easy wall mounting capabilities, this unit is designed for outdoor installation. It offers hot-start programming for quicker hot water and is compatible with a 1/2 gas line. The heater boasts a compact and lightweight design with industry-best side-to-side clearance.
Pros
- 7.0 GPM flow rate
- Liquid propane fueled
- Outdoor installation
- Compact and lightweight design
Cons
- This model is specifically for liquid propane and cannot be converted to natural gas.
This Rheem unit is an excellent option for properties that use liquid propane and require a high-efficiency outdoor tankless water heater. It’s well-dimensioned for homes with moderate hot water needs.
10. FOGATTI Natural Gas Tankless Water Heater Outdoor – Max 8.1
Best for: 8.1 GPM, Outdoor, Remote Control.
The FOGATTI tankless water heater is designed for outdoor natural gas installation, providing instant hot water at up to 8.1 GPM with an 180,000 BTU output. It ensures uninterrupted hot water supply for 3-5 outlets.
This unit features a durable build for outdoor conditions and includes a remote control panel for convenient indoor operation. The bottom-mounted fan aids in efficient exhaust. With CSA certification and 2-5 years of warranty, it offers both reliability and performance.
Pros
- 8.1 GPM instantaneous flow
- Outdoor-specific design
- Remote control for indoor operation
- 3-5 point hot water supply
Cons
- The 54 Watt-hour power consumption is higher than some competitors for similar flow rates.
This FOGATTI model is ideal for homeowners seeking a high-flow outdoor tankless water heater that can supply multiple fixtures simultaneously. The remote control feature offers added convenience.
Condensing vs. Non-Condensing: A False Economy for Outdoor Tankless
For any serious buyer of a best natural gas outdoor tankless water heater, the primary purchasing decision boils down to whether to opt for a condensing or non-condensing unit, and the economic argument for non-condensing units is often a trap.
While the initial cost of a non-condensing model like the Rheem RTG-70XLN-3 or the Westinghouse Natural Gas Tankless Water Heater Outdoor, 5.1 GPM 120,000 may seem appealing, this upfront saving is quickly erased by significantly lower energy efficiency over the lifespan of the appliance. Condensing units, such as the Rinnai RX199iN Condensing Smart Sense Natural Gas or Propane and the Rinnai CX199iN Condensing Smart Sense Commercial Natural Gas or Propane, recapture heat from exhaust gases that would otherwise be vented. This captured heat is used to preheat incoming cold water, drastically reducing the amount of natural gas required to reach the desired output temperature.
The difference in efficiency translates directly to lower utility bills month after month.
The 160,000 BTUs offered by the Rheem RTG-70XLN-3 and the 120,000 BTUs of the Westinghouse are ample power for many homes, but without the efficiency gains of condensation technology, that power is being consumed less judiciously. Conversely, a higher BTU unit like the FOGATTI Natural Gas Tankless Water Heater Outdoor – Max 8.1, while offering a robust 8.1 GPM flow rate, still benefits exponentially more from condensing technology than its non-condensing counterparts. The Rheem RTGH Series 8.4 GPM 157,000 BTU 120, also a high-flow option, underscores this point; its BTU output is impressive, but its efficiency hinges on the otherwise unmentioned technology that should be the buyer’s focus.
The argument for non-condensing units often centers on simpler installation and potentially lower maintenance, but that’s a shortsighted calculation. The long-term operational savings from a condensing unit, like the Rinnai models’ ability to handle both natural gas and propane with Smart Sense gas control systems, far outweigh any marginal increase in complexity or initial price. Think about it: the gas savings alone will amortize the difference in purchase price within a few years for most households.
Furthermore, newer condensing models are designed with serviceability in mind, as seen in the improved internal layouts and LED screens for diagnostics on units like the Rinnai RE199eN Non-Condensing Natural Gas Tankless Water Heater, Up to (though this specific model contradicts the core argument, it highlights evolving design principles). The added benefit of indoor/outdoor installation flexibility on the Rinnai RX199iN and CX199iN models also broadens their utility beyond just outdoor applications, a point not typically available with some non-condensing variants.
Ultimately, for maximizing long-term value and minimizing environmental impact, the Rinnai RX199iN Condensing Smart Sense Natural Gas or Propane is the most prudent choice for homeowners prioritizing efficiency and operational cost savings in an outdoor tankless system.
What to Look for in a Best Natural Gas Outdoor Tankless Water Heater
Gallons per minute gpm flow rate
For a single simultaneous use, such as a shower or faucet, aim for a minimum of 2.5 to 3.5 GPM. If your household frequently runs multiple appliances, like a shower, washing machine, and dishwasher concurrently, you’ll need a unit capable of 5 GPM or higher. Calculate your peak demand by adding the GPM requirements of your most frequently used fixtures.
A robust unit for a medium-sized family should target 5.5 to 8.5 GPM to ensure everyone enjoys uninterrupted hot water. Prioritize models specifying maximum flow rates that comfortably exceed your calculated peak needs.
Temperature rise capabilities
Your climate dictates the necessary temperature rise. In colder regions, you’ll need a heater that can raise water temperature by 70°F or more, while warmer areas might suffice with 40°F. Remember that GPM and temperature rise are inversely related; higher flow rates reduce the temperature increase.
Look for units that clearly state their temperature rise capabilities at various GPM outputs. For reliable performance even in winter, select a model engineered with advanced heat exchangers that maintain consistent output without significant performance drops, ensuring cozy showers year-round.
Unit dimensions and mounting
Assess your available outdoor space carefully. Tankless units are typically compact, but specific dimensions vary. Look for models with compact footprints if space is limited.
Crucially, check the required mounting method; most are designed for secure wall mounting using robust, corrosion-resistant brackets. Ensure the selected unit adheres to all manufacturer-specified clearance requirements for airflow and safe operation; typically, 12-24 inches are needed around the unit for ventilation and ease of maintenance, preventing operational issues and facilitating service.
Energy efficiency and ignition type
Energy efficiency is paramount for long-term savings. Seek units with a high Energy Factor (EF) rating, ideally 0.80 or above, indicating less wasted gas. For ignition, electronic ignition systems offer superior efficiency and reliability, automatically igniting the burner only when hot water is demanded, which conserves gas.
Hydrogenerated ignition, while viable, is less efficient. Prioritize models with electronic ignition and a high EF rating to minimize your gas consumption, ensuring both environmental responsibility and lower utility bills consistently.
Which Should You Choose?
- Confirm Gas Type: Ensure the unit is specifically designed for natural gas.
- Assess Flow Rate (GPM): Match the gallons per minute to your household’s simultaneous usage needs.
- Check Temperature Rise: Verify the heater can deliver the necessary temperature increase for your climate.
- Consider Installation Space: Measure your intended mounting location and any clearance requirements.
- Review Ignition Type: Electronic ignition is generally more efficient and reliable than pilot lights.
- Look for Outdoor Rating: Confirm the model is explicitly built for outdoor installation and weather resistance.
Quick Best Natural Gas Outdoor Tankless Water Heater Buying Checklist
Frequently Asked Questions
What Is The Primary Benefit Of An Outdoor Tankless Water Heater?
An outdoor tankless water heater provides on-demand hot water while saving indoor space. This separation also helps prevent potential water damage indoors and keeps operational noise away from living areas.
How Does The Gpm Affect Performance For A Natural Gas Outdoor Tankless Water Heater?
Gallons per minute (GPM) defines how much hot water the heater can supply simultaneously. Higher GPM is crucial for households with multiple simultaneous water demands, like running dishwashers and showers at once.
What Is A Typical Temperature Rise Capability For These Units?
Most natural gas outdoor tankless water heaters can achieve a temperature rise of 35-70°F. This range is generally sufficient for most climates and household hot water needs, even during colder months.
Are Outdoor Tankless Water Heaters More Energy-Efficient?
Yes, they offer enhanced energy efficiency because they only heat water when needed, eliminating standby heat loss from a traditional tank. This on-demand operation significantly reduces energy consumption.
What Maintenance Is Typically Required For A Natural Gas Outdoor Tankless Unit?
Regular maintenance involves flushing the unit annually to remove mineral buildup, especially in hard water areas. Checking gas connections and ensuring proper ventilation are also important to maintain optimal performance.
Final Words
Choosing the best natural gas outdoor tankless water heater offers significant advantages in space-saving and on-demand efficiency. These units provide a steady supply of hot water precisely when you need it, reducing energy waste. Investing in one can elevate your home’s comfort and utility.