The best natural gas outdoor tankless water heater delivers endless hot water on demand for homes with high simultaneous usage needs. Selecting the right unit ensures consistent temperatures and efficient operation, preventing wasted energy and frustrating performance dips. Factors like flow rate, temperature rise capabilities, and energy efficiency ratings vary significantly between models, impacting your comfort and utility bills.
An ill-chosen heater can lead to insufficient hot water during peak times or inefficient gas consumption. This guide presents our top picks to help you find the perfect outdoor tankless solution that meets your household’s specific demands without compromise, ensuring reliable heating for years to come.
For the best natural gas outdoor tankless water heater, consider models that offer high flow rates suitable for multiple simultaneous uses, such as the Rheem RTG-70XLN-3 (7.0 GPM) or the FOGATTI (up to 8.1 GPM), ensuring continuous hot water delivery for households with 2-3 bathrooms. The key decision criteria revolve around the GPM output, which directly correlates to the number of fixtures that can be used concurrently, and the BTUs, impacting heating efficiency.
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 usage homes | Check Price |
Best Pick 2  | NEW Rinnai RX199iN Condensing Smart Sense Natural Gas or Propane Best for: Smart home owners | Check Price |
Best Pick 3  | Westinghouse Natural Gas Tankless Water Heater Outdoor, 5.1 GPM 120,000 Best for: High water flow | Check Price |
Best Pick 4  | Rinnai CX199iN Condensing Smart Sense Commercial Natural Gas or Propane Best for: Business applications | 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
To identify the best natural gas outdoor tankless water heater, we prioritized build quality, real-world performance, safety, durability, and standout features. We ruled out models not specifically designed for outdoor natural gas use, such as propane-only units like the Rheem RTG-70XLP-Products with robust flow rates and dependable temperature control, like the Rheem RTGH Series and FOGATTI, were favored for strong performance.
We also considered advanced features such as smart technology and self-modulation for consistent hot water delivery, ensuring each recommendation offers exceptional value and reliability for years to come, at least through 2026.
What Most Buyers Get Wrong
Outdoor Venting and Gas Line Compatibility
When choosing a natural gas outdoor tankless water heater, ensure your chosen model is specifically designed for outdoor installation to prevent carbon monoxide buildup. While units like the Rheem RTG-70XLN-3 and Westinghouse Outdoor model are built for this, always verify. Additionally, confirm that your existing natural gas line can support the BTU requirements of the heater.
A unit like the FOGATTI with 180,000 BTU needs a robust supply, so check your home’s capacity before purchase to avoid performance issues.
Flow Rate for Your Home’s Needs
The GPM (gallons per minute) flow rate is crucial for tankless water heaters. For homes with 2-3 bathrooms, a flow rate of at least 7.0 GPM, like that offered by the Rheem RTG-70XLN-3 and the Rheem RTG-70DVLN-3 (though the latter is specified as indoor), is recommended to handle simultaneous use. If you have fewer fixtures or lower demand, a 5.1 GPM unit like the Westinghouse or MIZUDO might suffice.
Consider your peak hot water usage to select the appropriate GPM.
1. Rheem RTG-70XLN-3 High Efficiency Non-Condensing Outdoor Tankless Natural Gas Water
Best for: Ideal for 2-3 bathrooms simultaneously.
Delivering up to 7.0 GPM, this Rheem RTG-70XLN-3 offers consistent hot water for multiple simultaneous needs, such as showers and laundry, utilizing its powerful 160,000 BTUs with natural gas.
This non-condensing unit boasts a durable metal cabinet and supports wall mounting for outdoor installation by a qualified professional. Its hot-start program reduces initial cold water bursts, ensuring a more comfortable experience.
Pros
- 7.0 GPM flow rate for multi-fixture use
- 160,000 BTUs for rapid heating
- Outdoor installation design
- Hot-start program for comfort
Cons
- Requires professional installation for wall mounting
Homeowners needing reliable hot water for 2-3 bathrooms will find this unit a strong performer. Its outdoor design is perfect for maximizing indoor space.
2. NEW Rinnai RX199iN Condensing Smart Sense Natural Gas or Propane
Best for: Versatile indoor/outdoor, propane/natural gas.
This Rinnai RX199iN offers flexible installation indoors or outdoors with its Versa Vent system and operates on either natural gas or propane via its Smart Sense control, providing up to 11.1 GPM.
Compact yet powerful, this condensing unit is the size of a small suitcase and can support up to 7 fixtures concurrently. It operates with 199,000 BTUs and is smart home compatible.
Pros
- Dual fuel capability (NG/Propane)
- Indoor/outdoor installation flexibility
- Up to 11.1 GPM flow rate
- Smart home compatibility
Cons
- Requires RX-OVC vent cap for outdoor installation
For those requiring the utmost flexibility in fuel source and installation location, this model is an excellent choice. Its high GPM makes it suitable for larger homes.
3. Westinghouse Natural Gas Tankless Water Heater Outdoor, 5.1 GPM 120,000
Best for: Consistent temperature for smaller homes.
Providing 5.1 GPM and 120,000 BTU of on-demand hot water, this Westinghouse outdoor unit is designed for everyday home use, comfortably supporting 2-4 fixtures simultaneously.
Its advanced self-modulating technology maintains precise water temperature within ±1°F, ensuring consistent comfort. This CSA-certified unit comes with 2-5 years of after-sale support.
Pros
- Precise ±1°F temperature control
- 5.1 GPM capacity
- Outdoor installation
- CSA-certified
Cons
- Lower GPM may not support more than 4 fixtures
Homeowners prioritizing consistent water temperature for showers and everyday appliances will appreciate this model. Its outdoor design saves interior space.
4. Rinnai CX199iN Condensing Smart Sense Commercial Natural Gas or Propane
Best for: High-efficiency commercial or large-scale use.
With an impressive 97% thermal efficiency, this Rinnai CX199iN reduces energy costs while delivering up to 11.1 GPM with its 199,000 BTU output, suitable for commercial applications or large homes.
This condensing unit offers extensive installation flexibility and operates on natural gas. It boasts smart home compatibility and can maintain a maximum temperature of 185°F.
Pros
- 97% thermal efficiency for savings
- 11.1 GPM flow rate
- High maximum temperature (185°F)
- Smart home compatible
Cons
- Higher wattage (600 watts) than some models
Businesses or large households prioritizing energy efficiency and high demand will benefit from this unit. Its robust GPM ensures ample hot water.
5. Rheem RTG-70DVLN-3 High Efficiency Non-Condensing Indoor Tankless Natural Gas Water
Best for: Indoor installation, 2-3 bathroom homes.
Designed for indoor installation, this Rheem RTG-70DVLN-3, powered by natural gas with 160,000 BTUs, delivers up to 7.0 GPM, perfect for households with multiple simultaneous hot water needs.
This high-efficiency unit features a durable, compact metal cabinet and supports easy wall mounting. It includes an integrated digital display and hot-start programming for enhanced user experience.
Pros
- 7.0 GPM flow rate
- 160,000 BTUs heating power
- Indoor installation suitability
- Integrated digital display
Cons
- Not smart home compatible
Suitable for homes with 2-3 bathrooms, this indoor unit provides ample hot water for daily demands. Its compact design allows for discreet placement.
6. Rinnai RE199eN Non-Condensing Natural Gas Tankless Water Heater, Up to
Best for: Energy-saving for moderate use.
This Rinnai RE199eN non-condensing tankless water heater heats only when necessary to conserve energy, providing up to 7.6 GPM with a natural gas output of 199,000 BTUs.
Sized like a small suitcase, this unit features an LED screen for service reminders and error codes, simplifying maintenance. It’s designed for outdoor installation and provides 6 fixtures capacity.
Pros
- Energy conservation by heating on demand
- 7.6 GPM flow rate
- LED display for service
- Compact design
Cons
- Lower efficiency rating (0.81)
This model is ideal for homeowners seeking energy savings and moderate hot water needs for up to 6 fixtures. Its outdoor design is practical.
7. Rheem RRTGH84DVLN3701171 Rheem RTGH Series 8.4 GPM 157,000 BTU 120
Best for: High flow rate for busy households.
With a flow rate ranging from 0.4 to 8.4 GPM, this Rheem RTGH Series unit is powered by natural gas and delivers 157,000 BTU, suitable for homes with significant hot water demands.
This model features exclusive hot start programming and overheat film wrap for safety and comfort. It includes electric ignition and comes with comprehensive manufacturer warranties.
Pros
- Up to 8.4 GPM flow rate
- 157,000 BTU heat output
- Exclusive hot start programming
- Electric ignition
Cons
- Labor warranty is only 1 year
Families with high simultaneous hot water needs will benefit from the robust performance of this Rheem unit. Its 8.4 GPM capacity handles multiple demands.
8. MIZUDO Natural Gas Tankless Water Heater Outdoor Installation Max 5.1
Best for: Consistent temperature, outdoor setup.
The Mizudo Gen 2 outdoor tankless water heater uses upgraded temperature control to maintain a ±1°F difference with 5.1 GPM at 120,000 BTU, ensuring a constant and comfortable bathing experience.
This natural gas unit automatically self-modulates water temperature via its gas valve, water volume servo, and built-in chip, providing endless hot water. It includes automatic anti-freezing protection and CSA certification.
Pros
- Precise ±1°F temperature stability
- 5.1 GPM flow rate
- Automatic anti-freezing protection
- CSA Certified
Cons
- Lower BTU output compared to some competitors
For consistent, comfortable hot water outdoors, this Mizudo model is a great option. Its precise temperature control is ideal for discerning users.
9. Rheem RTG-70XLP-3 High Efficiency Non-Condensing Outdoor Tankless Liquid Propane Water
Best for: Outdoor installation, 2-3 bathroom homes.
This Rheem RTG-70XLP-3, powered by liquid propane with 160,000 BTUs, delivers up to 7.0 GPM, ideal for 2-3 bathroom homes with multiple hot water demands like showers and laundry.
Designed for outdoor installation, this high-efficiency unit features a durable metal cabinet and supports easy wall mounting. It includes hot-start programming for reduced cold water bursts.
Pros
- 7.0 GPM flow rate
- 160,000 BTUs of power
- Outdoor installation design
- Hot-start programming
Cons
- Requires liquid propane fuel source
Ideal for homes with up to three bathrooms utilizing liquid propane, this unit offers consistent hot water. Its outdoor placement is space-saving.
10. FOGATTI Natural Gas Tankless Water Heater Outdoor – Max 8.1
Best for: Instant hot water for 3-5 outlets.
The FOGATTI tankless water heater provides instant hot water with a 180,000 BTU output and up to 8.1 GPM flow rate, ensuring uninterrupted hot water for showers, sinks, and appliances.
Built for outdoor durability, this natural gas unit comes with a remote control panel for convenient indoor operation and features a bottom-mounted fan. It supports 3-5 hot water outlets simultaneously.
Pros
- Up to 8.1 GPM flow rate
- 180,000 BTU heating power
- Outdoor durability
- Remote control panel
Cons
- Higher wattage (54 Watt-hours) for AC power
This FOGATTI water heater is perfect for households needing instant, continuous hot water for multiple points of use. Its outdoor design is robust.
BTU Wattage vs. GPM Flow Rate
When selecting a natural gas outdoor tankless water heater, the fundamental trade-off boils down to prioritizing sustained hot water volume versus the sheer speed at which water can be heated. Most buyers focus on the advertised Gallons Per Minute (GPM) for simultaneous use, but overlook how BTU input directly dictates that capability, and ultimately, the unit’s effectiveness in colder climates or during peak demand. A higher BTU rating, such as the 160,000 BTUs found in the Rheem RTG-70XLN-3 and Rheem RTG-70XLP-3, allows the water to be heated more aggressively, ensuring that even at lower incoming water temperatures, the output remains sufficient for multiple fixtures.
Without adequate BTU input, a high GPM rating becomes a theoretical maximum rather than a practical reality.
Consider the Westinghouse Natural Gas Tankless Water Heater Outdoor, 5.1 GPM 120,000, and the MIZUDO Natural Gas Tankless Water Heater Outdoor Installation Max 5.Both list a 5.1 GPM flow rate, which is adequate for a single shower or faucet. However, their lower 120,000 BTU output means they will struggle significantly more when ambient temperatures dip, or if a user wants to run a shower while the dishwasher is also cycling.
The FOGATTI Natural Gas Tankless Water Heater Outdoor – Max 8.1, with its robust 180,000 BTU output, is better positioned to handle demanding situations and maintain its 8.1 GPM flow even under duress, making it a more versatile choice for homes with higher hot water consumption patterns or those in less temperate regions.
The Rinnai offerings, particularly the Rinnai RX199iN Condensing Smart Sense and Rinnai CX199iN Condensing Smart Sense Commercial, and the Rinnai RE199eN Non-Condensing Natural Gas Tankless Water Heater, Up to, generally offer impressive GPM ratings. However, the crucial distinction lies less in their GPM figures and more in their BTU input and whether they are condensing or non-condensing. For raw heating power that translates directly to on-demand hot water capacity across varying conditions, units like the Rheem RRTGH84DVLN3701171, boasting 8.4 GPM and 157,000 BTU, showcase the higher end of this spectrum, effectively bridging the gap between high flow and necessary heating power.
Neglecting the BTU input is the most common oversight, leading to disappointment when the heater cannot perform to expectations, especially during harsh winters.
Ultimately, while GPM numbers capture the imagination by promising simultaneous use, it is the BTU Wattage that underpins that promise. For robust performance that consistently delivers hot water regardless of incoming water temperature or concurrent usage, prioritize models with higher BTU ratings. If your primary concern is maintaining a steady flow for multiple applications even in colder weather, the FOGATTI Natural Gas Tankless Water Heater Outdoor – Max 8.1 delivers superior heating capacity.
What to Look For in a Natural Gas Outdoor Tankless Water Heater
Flow rate and gallons per minute gpm
For single-fixture use, prioritize a natural gas tankless heater with at least 5.0 GPM. This ensures uninterrupted hot water for showers or dishwashing. If you anticipate multiple simultaneous uses, such as a shower running while a dishwasher cycles, aim for 8.0 GPM or higher.
In colder climates or at higher elevations, select a unit with a higher GPM rating to compensate for increased heating demand; a 9.5 GPM unit is optimal for these conditions. For most households, a unit offering 8.0 GPM at a 45°F rise is the best balance of capacity and efficiency.
Temperature rise capabilities
Consider your climate’s typical incoming water temperature to determine the necessary temperature rise. For mild climates, a 70°F rise is sufficient, while colder regions demand a 90°F rise or more. Crucially, look beyond the maximum temperature rise and examine GPM at that peak.
A unit rated for 7.0 GPM at a 90°F rise is superior for cold climates than one rated at 5.0 GPM. The performance is directly tied to how much heat the water needs; prioritize units that maintain high GPM even under challenging temperature differentials, making 7.0 GPM at 90°F the best choice for most colder areas.
Energy efficiency and ignition type
When selecting an energy-efficient natural gas tankless heater, focus on the Energy Factor (EF) rating; aim for an EF of 0.80 or higher. Pilotless ignition systems are always superior, eliminating energy waste from a constantly burning pilot light. This direct ignition method ensures immediate heating only when needed.
For optimal gas consumption and cost savings, choose a unit with a high EF and electronic ignition; this combination guarantees that your heater operates efficiently, delivering hot water without unnecessary fuel expenditure. The best choice is a unit with an EF above 0.82 and electronic ignition.
Which Should You Choose?
- If you have a larger home with 3 or more bathrooms, choose a model with a flow rate of at least 7.0 GPM.
- If you need a versatile unit that can be installed indoors or outdoors and run on different gas types, look for models with advanced venting and smart sensing technology.
- If you prioritize energy efficiency and want a heater that only works when needed, seek out models with energy-saving features and an electronic ignition.
- If you have a smaller home or are looking for a unit primarily for basic everyday use like single showers or sinks, a model with a flow rate around 5.1 GPM should suffice.
Quick Best Natural Gas Outdoor Tankless Water Heater Buying Checklist
- Check GPM Needs: Ensure the heater meets your household’s peak demand for simultaneous use.
- Verify Temperature Rise: Select a unit that can adequately heat water for your climate’s incoming temperatures.
- Review Energy Factor: Look for higher EF ratings to ensure operational cost savings.
- Consider Ignition Type: Electronic ignition is generally more efficient and reliable than pilot lights.
- Assess Venting Requirements: Understand the necessary venting for safe and proper installation.
- Confirm Durability: Opt for models constructed with corrosion-resistant materials for outdoor use.
Frequently Asked Questions
What Is The Primary Benefit Of An Outdoor Tankless Water Heater?
Outdoor tankless water heaters provide on-demand hot water, maximizing energy efficiency by only heating water when needed. This design saves space and frees up indoor living areas, making them ideal for diverse homeowner needs.
How Does Gpm Affect Performance For An Outdoor Tankless Unit?
Gallons Per Minute (GPM) determines how much hot water the unit can deliver simultaneously. A higher GPM is crucial for households with multiple bathrooms orAppliances that use hot water at the same time to avoid lower temperatures.
What Is An Optimal Temperature Rise For An Outdoor Tankless Water Heater?
An optimal temperature rise for most outdoor tankless units is between 45-70°F, depending on your climate and incoming water temperature. This range ensures hot water is available even during colder months for showers and other uses.
Are Natural Gas Outdoor Tankless Water Heaters Energy Efficient?
Yes, natural gas outdoor tankless water heaters are highly energy efficient because they only heat water as needed, unlike traditional tank heaters that constantly maintain water temperature. This on-demand heating reduces wasted energy and can lower utility bills.
What Are The Venting Requirements For Outdoor Tankless Water Heaters?
Outdoor tankless water heaters typically require specialized venting kits for safe operation, often stainless steel or PVC pipes, to expel combustion gases away from the home. Proper installation according to manufacturer guidelines is essential for safety and efficiency.
Final Words
Investing in the best natural gas outdoor tankless water heater offers unparalleled convenience and efficiency for your home. Enjoy endless hot water while saving energy and valuable indoor space. Upgrade your water heating system today and experience the modern, on-demand comfort that tankless technology provides.