Best Natural Gas Tankless Water Heaters (Top 10)

The best natural gas outdoor tankless water heater provides efficient, continuous hot water precisely when and where you need it, perfect for cabins, pools, or remote wash stations. While the core benefit of on-demand heating remains, significant variations exist between models in terms of heating capacity, energy efficiency ratings, and durability. Choosing the wrong unit can lead to insufficient hot water supply or premature failure, wasting both energy and your investment.

We’ve researched and compiled a list of the top 10 options to help you find the ideal solution for your specific outdoor heating requirements this 2026.

For the best natural gas outdoor tankless water heater, consider models offering a high GPM flow rate to meet multiple hot water demands. The Rheem RTG-70XLN-3 stands out for delivering up to 7.0 GPM, suitable for homes with 2–3 bathrooms, powered by natural gas with 160,000 BTUs.

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: Small homes	Check Price
Best Pick 2	NEW Rinnai RX199iN Condensing Smart Sense Natural Gas or Propane Best for: Smart homes	Check Price
Best Pick 3	Westinghouse Natural Gas Tankless Water Heater Outdoor, 5.1 GPM 120,000 Best for: High flow	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 use	Check Price

How We Picked

To identify the best natural gas outdoor tankless water heater, we prioritized build quality, real-world performance, safety, durability, and standout features. We considered models like the Rheem RTG-70XLN-3 and Westinghouse for their specific GPM ratings suitable for multiple bathrooms. Models with advanced safety features and robust construction were favored.

Condensing units were noted for energy efficiency, while non-condensing options were assessed for straightforward installation. Units capable of handling demanding usage, as suggested by their BTU output, were central to our evaluation, ultimately guiding our selection based on sustained performance and reliability.

What Most Buyers Get Wrong

Outdoor Installation Requires Unobstructed Airflow

Crucial for natural gas outdoor tankless water heaters, proper ventilation prevents dangerous gas buildup and ensures efficient combustion. Unlike indoor models that rely on existing venting systems, outdoor units need ample space around them for fresh air intake and exhaust. Factors like nearby walls, foliage, or structures can impede this.

Always check the manufacturer’s clearance recommendations, such as those for the Rheem RTG-70XLN-3 or Westinghouse 5.1 GPM models, to guarantee safe and optimal performance.

Understanding GPM for Your Household Demand

When selecting a natural gas outdoor tankless water heater, the Gallons Per Minute (GPM) rating is paramount for meeting simultaneous hot water needs. A higher GPM means more hot water can be delivered at once. For instance, the Rheem RTGH Series with 8.4 GPM is designed for larger homes with multiple usage points, while a unit like the MIZUDO or Westinghouse at 5.1 GPM might suffice for smaller households or point-of-use applications.

Consider how many showers, faucets, or appliances you run concurrently to avoid lukewarm surprises.

1. Rheem RTG-70XLN-3 High Efficiency Non-Condensing Outdoor Tankless Natural Gas Water

Best for: 2-3 bath homes needing high-volume hot water.

This Rheem RTG-70XLN-3 provides 7.0 GPM to support simultaneous hot water use across 2-3 bathrooms, ensuring your showers and laundry never compete for heat. Its natural gas power with 160,000 BTUs delivers fast, reliable on-demand hot water.

Featuring a durable metal cabinet for outdoor installation, this unit boasts high efficiency with a low activation flow rate. Its technical specifications include a maximum temperature of 140°F and self-diagnostic programs for straightforward operation.

Pros

• 7.0 GPM flow rate for multiple fixtures
• 160,000 BTUs for rapid heating
• Durable metal cabinet for outdoor longevity
• Self-diagnostic program for easier maintenance

Cons

• Requires installation by a qualified installer.

Ideal for homeowners with 2-3 bathrooms that frequently experience high hot water demand. This Rheem unit offers a solution for consistent, on-demand hot water for all household needs.

2. NEW Rinnai RX199iN Condensing Smart Sense Natural Gas or Propane

Best for: Versatile indoor/outdoor use with Smart Sense technology.

The Rinnai RX199iN offers installation flexibility for either indoor or outdoor placement, accommodating both natural gas and propane with its Smart Sense gas control system. This compact unit provides up to 11.1 GPM.

Measuring roughly the size of a small suitcase, this condensing tankless unit can support up to 7 fixtures simultaneously. It operates on 120 Volts (98 watts) and reaches a maximum of 140°F with a substantial 199,000 BTUs of heat output.

Pros

• Indoor/outdoor installation flexibility
• Dual fuel capability (NG/Propane)
• Up to 11.1 GPM flow rate
• Compact, suitcase-sized design

Cons

• Outdoor installation requires an RX-OVC vent cap (sold separately).

Perfect for homeowners seeking a versatile unit that can be installed virtually anywhere. Its high flow rate makes it suitable for busy households with multiple simultaneous hot water demands.

3. Westinghouse Natural Gas Tankless Water Heater Outdoor, 5.1 GPM 120,000

Best for: Consistent temperature for everyday home use.

This Westinghouse outdoor natural gas tankless water heater delivers up to 5.1 GPM with 120,000 BTU, providing endless hot water for everyday home use such as showers and laundry. Its advanced self-modulating technology maintains precise temperature control.

Achieve ±1°F temperature stability thanks to its self-modulating technology, ensuring a comfortable and consistent water temperature. This unit supports up to 150 PSI and is CSA-Certified, offering reliable performance for up to 4 fixtures simultaneously.

Pros

• Precise ±1°F temperature control
• 5.1 GPM flow rate for multi-fixture use
• 120,000 BTU heat output
• CSA-Certificated for safety and compliance

Cons

• Flow rate of 5.1 GPM may be insufficient for very high-demand simultaneous usage.

This Westinghouse heater is a solid choice for households needing reliable, on-demand hot water with precise temperature regulation. It’s well-suited for managing showers, sinks, and appliances without temperature fluctuations.

4. Rinnai CX199iN Condensing Smart Sense Commercial Natural Gas or Propane

Best for: Commercial applications and high-efficiency demands.

The Rinnai CX199iN offers a super high efficiency rating of 97% for reduced energy costs, designed for commercial applications or homes with significant hot water needs. It provides 11.1 GPM with 199,000 BTUs.

This condensing model is suitable for indoor or outdoor installation with its Versa Vent system and Smart Sense gas control, compatible with natural gas. It operates on 120 Volts (600 watts) and can reach a maximum temperature of 185°F.

Pros

• 97% thermal efficiency for energy savings
• 11.1 GPM flow rate for high demand
• 199,000 BTU heat output
• Indoor/outdoor installation versatility

Cons

• Higher wattage (600W) electrical requirement compared to some models.

An excellent option for commercial settings or large homes prioritizing energy efficiency and high hot water output. Its robust performance and flexible installation make it a top-tier choice for demanding environments.

5. Rheem RTG-70DVLN-3 High Efficiency Non-Condensing Indoor Tankless Natural Gas Water

Best for: Indoor installation for 2-3 bathroom homes.

The Rheem RTG-70DVLN-3 is designed for indoor installation, delivering 7.0 GPM of on-demand hot water, ideal for homes with 2-3 bathrooms and multiple simultaneous needs like showers and laundry. Powered by natural gas with 160,000 BTUs.

This high-efficiency unit features a compact, durable metal cabinet and supports easy wall mounting. Its technical specifications include universal venting compatibility, 1/2 gas line compatibility, and hot-start programming to minimize cold water bursts.

Pros

• 7.0 GPM flow rate for 2-3 bathrooms
• 160,000 BTUs for fast heating
• Compact design for indoor mounting
• Hot-start programming for comfort

Cons

• Not designed for outdoor installation.

This Rheem heater is perfect for homeowners looking to upgrade their indoor hot water system for a 2-3 bathroom household. It ensures consistent hot water delivery for showers and appliances without interruption.

6. Rinnai RE199eN Non-Condensing Natural Gas Tankless Water Heater, Up to

Best for: Energy-saving outdoor unit with up to 7.6 GPM.

The Rinnai RE199eN heats water only when necessary to conserve energy, featuring an LED screen for service reminders and error codes. This non-condensing outdoor unit provides up to 7.6 GPM for up to 6 fixtures.

This tankless water heater boasts a flow rate of 9.8 GPM, supporting simultaneous use across multiple fixtures. With a heat output of 199,000 BTUs and a maximum temperature of 140°F, it’s an efficient and reliable choice for outdoor use.

Pros

• Energy conservation by heating on demand
• 7.6 GPM flow rate for 6 fixtures
• LED screen for diagnostics
• Smart, durable design

Cons

• Efficiency rating of 0.81 may not be as high as condensing models.

Homeowners seeking an energy-conscious outdoor hot water solution will appreciate this Rinnai model. It’s designed to provide ample hot water for a medium-sized household while optimizing energy usage.

7. Rheem RRTGH84DVLN3701171 Rheem RTGH Series 8.4 GPM 157,000 BTU 120

Best for: High flow rate for busy households with 157,000 BTU.

The Rheem RTGH Series offers an impressive flow rate of 0.4 to 8.4 GPM, ideal for homes requiring substantial hot water delivery for multiple appliances and fixtures simultaneously. It features an output of 157,000 BTUs.

With available temperature settings from 100 to 140°F, default set at 120°F, this unit ensures user-defined comfort. Its design includes exclusive hot start programming and overheat film wrap for enhanced safety and performance.

Pros

• High 8.4 GPM flow rate
• 157,000 BTU heating capacity
• Exclusive hot start programming
• Overheat film wrap for safety

Cons

• Limited warranty of 1 year labor, 15 years heat exchanger.

This Rheem model is perfect for larger homes or those with high simultaneous hot water demands, such as multiple showers running at once. Its robust flow rate ensures no one is left out of hot water.

8. MIZUDO Natural Gas Tankless Water Heater Outdoor Installation Max 5.1

Best for: Outdoor installation with precise ±1°F temperature control.

The MIZUDO Gen 2 outdoor gas tankless water heater precisely self-modulates water temperature within ±1°F, ensuring a consistently comfortable bathing experience. It delivers up to 5.1 GPM at 120,000 BTU.

This upgraded Gen 2 model uses an integrated chip, gas proportional valve, and water volume servo for accuracy. It features automatic anti-freezing protection and offers 2 years of support for the whole unit and 5 years for the heat exchanger.

Pros

• Precise ±1°F temperature stability
• 5.1 GPM flow rate
• Automatic anti-freezing protection
• CSA Certificated for safety

Cons

• Limited to 5.1 GPM, which may be insufficient for very high-demand households.

Ideal for homeowners prioritizing precise temperature control for their outdoor hot water needs. This Mizudo heater provides a stable and comfortable temperature for bathing and other household uses.

9. Rheem RTG-70XLP-3 High Efficiency Non-Condensing Outdoor Tankless Liquid Propane Water

Best for: Outdoor installation with 160,000 BTU for propane.

This Rheem RTG-70XLP-3 tankless water heater operates on liquid propane, offering 7.0 GPM for 2-3 bathroom homes where high hot water demand is common. Its 160,000 BTU output ensures fast, reliable heating.

Designed for outdoor installation with a durable metal cabinet, this unit features a compact and lightweight design with industry-best side-to-side clearance. It includes hot-start programming for consistent temperatures and 1/2 gas line compatibility.

Pros

• 7.0 GPM flow rate for multiple fixtures
• 160,000 BTU heating capacity
• Liquid propane fuel source
• Compact and lightweight outdoor design

Cons

• Uses liquid propane, which has different supply and cost considerations than natural gas.

Perfect for properties that utilize liquid propane and need a reliable outdoor tankless water heater for a 2-3 bathroom home. It ensures sufficient hot water for showers, laundry, and more.

10. FOGATTI Natural Gas Tankless Water Heater Outdoor – Max 8.1

Best for: Outdoor unit with 8.1 GPM and remote control.

The FOGATTI natural gas tankless water heater provides instant, continuous hot water with up to 8.1 GPM flow rate, powered by 180,000 BTU. Designed for outdoor durability, it includes a remote control panel for convenient indoor operation.

This model can supply hot water to 3-5 outlets simultaneously, ensuring uninterrupted flow for showers, sinks, and appliances. It boasts CSA certification and energy-saving high efficiency, with a warranty ranging from 2 to 5 years.

Pros

• High 8.1 GPM flow rate
• 180,000 BTU heating power
• Outdoor-specific durable design
• Remote control panel for convenience

Cons

• The bottom-mounted fan might be a consideration for placement in certain outdoor locations.

This FOGATTI heater is ideal for larger homes or properties with high hot water demand, especially those with outdoor installation requirements. The remote control adds a layer of convenience for operation.

Condensing vs. Non-Condensing For Outdoor Gas Tankless

The primary determinant of long-term satisfaction with a best natural gas outdoor tankless water heater rests on understanding the fundamental difference between condensing and non-condensing models and how that impacts your specific installation site.

While both Rinnai RX199iN Condensing Smart Sense Natural Gas or Propane and Rinnai CX199iN Condensing Smart Sense Commercial Natural Gas or Propane offer the advanced condensation technology that recaptures heat from exhaust gases to pre-heat incoming water, thereby achieving higher energy efficiency (often above 90%), this comes with a critical installation caveat. Condensing units produce acidic wastewater that must be properly drained, which can add complexity and cost to an outdoor setup, especially in regions with freezing temperatures. In contrast, non-condensing units like the Rheem RTG-70XLN-3 High Efficiency Non-Condensing Outdoor Tankless Natural Gas Water, the Westinghouse Natural Gas Tankless Water Heater Outdoor, 5.1 GPM 120,000, and the Rinnai RE199eN Non-Condensing Natural Gas Tankless Water Heater, Up to, are simpler.

They exhaust gases directly, requiring less intrusive plumbing, making them arguably more straightforward for many outdoor applications where managing condensate is a concern.

For an outdoor installation, particularly if you are looking for the path of least resistance regarding plumbing and potential freezing issues, a robust non-condensing unit often presents a more practical choice. The Rheem RTGH Series 8.4 GPM 157,000 BTU 120, for instance, delivers a high flow rate without the added complexity of condensate management. Similarly, the FOGATTI Natural Gas Tankless Water Heater Outdoor – Max 8.1, with its 8.1 GPM capacity, is designed for significant hot water demand and, as a non-condensing model, prioritizes simpler integration.

While condensing technology represents a leap in energy efficiency, it’s not a universal upgrade for every outdoor setting. The added wastewater management can introduce vulnerabilities and expenses that negate its primary benefit in less-than-ideal outdoor environments. Homeowners prioritizing ease of installation and minimizing potential maintenance related to drainage might find a high-performance non-condensing model like the Rheem RTG-70XLN-3 to be the superior choice.

What to Look for in a Best Natural Gas Outdoor Tankless Water Heater

Flow rate and gpm

For uninterrupted hot water, prioritize a minimum flow rate of 5.0 GPM, essential for running multiple fixtures. If your household has high simultaneous demand, such as multiple showers or a dishwasher running concurrently, select a unit rated at 7.0 GPM. Always verify that this GPM is achieved at a 45°F temperature rise from the incoming water.

For warmer regions, note the GPM at a lower temperature rise, but for a robust, multi-point-of-use experience, a 7.0 GPM at 45°F rise is the definitive choice for superior performance.

Energy factor ef and efficiency

Maximize your savings by choosing a water heater with an Energy Factor (EF) of 0.80 or higher. This metric directly reflects how efficiently the unit converts gas into usable hot water. A higher EF signifies less wasted energy, translating into significantly lower monthly utility bills.

When comparing models, always look at the stated EF to ensure you invest in an economical and environmentally conscious appliance. An EF of 0.85 or greater offers the best long-term value and operational efficiency.

Thermostatic control and features

Precise temperature management is key; opt for models featuring digital displays that allow for exact thermostat settings, eliminating guesswork. For ultimate convenience, seek units with remote control capabilities, enabling adjustments from inside your home. In colder climates, built-in freeze protection is non-negotiable to prevent damage.

Models with integrated fans for venting efficiency are also superior for ensuring optimal performance and easier installation. A unit with a digital display and freeze protection is the ideal selection for comfort and reliability.

Physical dimensions and installation

When selecting a unit, consider its physical footprint to ensure it integrates seamlessly into your outdoor space. Pay close attention to venting requirements; horizontal venting is typically simpler for many outdoor installations. Crucially, confirm the unit’s gas line size compatibility; undersized lines will restrict performance.

For straightforward outdoor placement and sustained performance, a unit with a compact design and versatile venting options, paired with standard gas line requirements, is the most practical and efficient choice for most residential applications.

Which Should You Choose?

• If your home has 2-3 bathrooms and frequently runs multiple hot water appliances simultaneously, choose a model with a flow rate of at least 7.0 GPM and a BTU output of 160,000 or higher.
• If you need a versatile unit that can be installed indoors or outdoors and can run on either natural gas or propane, look for models with “Smart Sense” gas control and features like “Versa Vent” technology.
• If you’re looking for basic on-demand hot water for everyday home use with shower and sink needs, a model with a GPM of around 5.1 and a BTU output of 120,000 should suffice.
• If you need a higher flow rate for a larger home or more simultaneous hot water demands, consider a unit capable of 8.4 GPM with a BTU output around 157,000 or more.

Quick Best Natural Gas Outdoor Tankless Water Heater Buying Checklist

• Assess Your Hot Water Needs: Determine how many fixtures you’ll use simultaneously to select the appropriate Gallons Per Minute (GPM).
• Check the Energy Factor (EF): Aim for an EF of 0.80 or higher for optimal energy efficiency and lower operating costs.
• Verify Thermostatic Controls: Ensure your chosen unit offers precise temperature control for consistent hot water.
• Consider Installation Requirements: Understand the venting options and physical space needed for proper setup.
• Look for Freeze Protection: If you live in a colder climate, ensure the unit has robust freeze protection features.
• Read User Reviews: Gain insights into real-world performance, reliability, and ease of use from other owners.

Frequently Asked Questions

What Is The Minimum Gpm Required For A Household?

A minimum of 5.0 GPM is generally recommended for a household to handle multiple fixtures simultaneously. This flow rate ensures you can run a shower and sink at the same time without a significant drop in hot water temperature.

How Does The Energy Factor (Ef) Affect My Utility Bills?

The Energy Factor (EF) indicates the unit’s efficiency in converting gas to hot water. A higher EF, such as 0.80 or more, means less energy is wasted, directly leading to lower monthly gas bills.

Are Outdoor Tankless Water Heaters Safe In Freezing Temperatures?

Many models are equipped with freeze protection, automatically activating a low-level heat to prevent pipes from freezing. Always check the specific product’s features, as this capability is essential for colder climates.

What Kind Of Venting Is Typically Needed For These Units?

Outdoor tankless units commonly use either horizontal or vertical venting, depending on the model and installation location. Ensure the chosen unit’s venting system is compatible with your outdoor setup and local building codes.

Can I Control The Temperature Precisely With These Heaters?

Yes, most modern units feature digital displays for precise temperature selection, allowing you to set your desired hot water temperature accurately. Some also offer remote control options for added convenience.

Final Words

Investing in the best natural gas outdoor tankless water heater offers an efficient and on-demand supply of hot water. Enjoy the benefits of continuous hot water and potential energy savings. Upgrade your home’s comfort and convenience with a reliable tankless solution today.