Takagi T-H3S-OS-N Condensing High Efficiency Alternatives: 6 Similar Picks Compared
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The Takagi T-H3S-OS-N is a condensing high efficiency alternative for outdoor natural gas water heating. It delivers 8 GPM in a compact 24.9-inch height unit. This model meets ultra-low NOx emission standards. You might seek different specs, such as propane fuel or non-condensing venting. Some buyers need higher flow rates or a narrower footprint for tight spaces. Others prefer a different brand for specific reliability or feature sets. We selected these 6 options because their published specifications overlap with the original unit. Each pick shares key traits like outdoor installation capability and natural gas or propane compatibility. This list helps you compare flow rates, dimensions, and venting types directly. You can find a unit that better matches your home’s specific hot water demands. The alternatives cover a range of capacities from 6.8 to 10 GPM. They include both condensing and non-condensing technologies. This variety ensures you can find a practical solution for your outdoor space.
Our top pick: Takagi Outdoor 8 GPM Natural Gas Water Heater.
Key differences for your needs
Takagi T-H3M Outdoor Natural Gas Heater
The Takagi T-H3M-OS-N narrows the width to 13.1 inches, making it ideal for tight outdoor spaces. It shares the condensing venting and natural gas fuel type with the T-H3S-OS-N. However, it does not list a specific flow rate in the provided data, so you cannot confirm if it matches the 8 GPM output. It is lighter at 44 pounds. This model suits homeowners with limited wall space who still want high-efficiency condensing technology. It offers a similar footprint in height but trades width for compactness.
Takagi Outdoor Propane Tankless Water Heater
The Takagi T-H3S-OS-P matches the 8 GPM capacity and dimensions of the T-H3S-OS-N exactly. The key difference is the fuel type. This unit runs on propane instead of natural gas. It also weighs 69 pounds, which is heavier than the gas version. You should choose this alternative if your outdoor location has a propane supply but lacks natural gas lines. The condensing efficiency and ultra-low NOx emissions remain consistent with the original model, ensuring similar environmental performance.
Rheem RTG 9.5 GPM Outdoor Natural Gas Tankless Heater
The Rheem RTG-95XLN-3 increases the flow rate to 9.5 GPM, offering more hot water than the 8 GPM Takagi. It uses non-condensing venting, which simplifies installation compared to the condensing design of the T-H3S-OS-N. It is smaller in height at 20.8 inches and includes WiFi connectivity. This unit weighs less at 39.3 pounds. You should pick this model if you need higher flow rates or prefer non-condensing venting for easier maintenance. It sacrifices the ultra-low emission compliance of the Takagi for increased capacity and simpler venting.
Rinnai RU160eN 9 GPM Outdoor Natural Gas
The Rinnai RU160eN provides 9 GPM, exceeding the 8 GPM output of the T-H3S-OS-N. It shares the condensing venting and natural gas fuel type. However, it is significantly larger, standing 33.9 inches tall and weighing 71 pounds. You will need to purchase the recirculation pump and Wi-Fi module separately, as they are not included. This alternative suits homes needing higher flow rates for multiple appliances. It offers similar efficiency but requires more space and additional accessories for full functionality.
A. O. Smith 10 GPM Outdoor Condensing Tankless Heater
The A. O. Smith ATO-540H-N delivers 10 GPM, providing higher capacity than the 8 GPM Takagi. It features a 199,000 BTU input and a copper heat exchanger. It includes a remote control, which the T-H3S-OS-N does not list. The unit is 23.6 inches tall and weighs 59 pounds. You should choose this model if you need maximum hot water flow and want remote monitoring capabilities. It maintains condensing efficiency for outdoor use but offers greater power and convenience features for larger households.
Rheem 6.8 GPM Outdoor Condensing Water Heater
The Rheem RTGH-68XLN-2 offers 6.8 GPM, which is lower than the 8 GPM Takagi. It shares the condensing venting and natural gas fuel type. It is narrower at 9.75 inches but taller at 28.5 inches. It weighs 77 pounds, making it the heaviest option listed. This unit is designed for cold climates with specific safety features. You should pick this alternative if you have lower hot water demands or need a narrower profile for tight installations. It sacrifices flow rate for specialized cold-climate performance and compact width.
Quick picks
Our 7 picks
Takagi Outdoor 8 GPM Natural Gas Water Heater
Best for: outdoor homes needing efficient hot water
- Fuel Type
- Natural Gas
- Flow Rate
- 8 GPM
- Installation Location
- Outdoor
- Dimensions
- 24.9 x 17.8 x 11.3 inches
- Venting Type
- Condensing
- Capacity
- 8 Gallon
View on Amazon: Takagi Outdoor 8 GPM Natural Gas Water Heater Affiliate link
This Takagi unit delivers 8 GPM of hot water using natural gas. It is designed for outdoor installation and features condensing technology for high efficiency. The device meets strict 2012 SCAQMD Rule 1146.2 standards for ultra-low NOx emissions. Its compact dimensions of 24.9 x 17.8 x 11.3 inches allow for space-saving placement. You get endless hot water without a pilot light.
Pros
- 8 GPM flow rate for simultaneous use
- Condensing technology for high efficiency
- Meets 2012 SCAQMD Rule 1146.2 emissions standards
- Outdoor-rated design
- No pilot light required
Cons
- 8 GPM is lower than the 9.5 GPM Rheem RTG Series
- Outdoor installation only, not suitable for indoor use
- No remote control or app connectivity listed
Good fit if
- You need high efficiency for outdoor installation
- You require compliance with strict NOx emissions rules
- You want a natural gas unit with 8 GPM capacity
Skip if
- You need indoor installation capability
- You require more than 8 GPM flow rate
- You prefer propane fuel over natural gas
Verdict: Takagi 8 GPM Outdoor Natural Gas Heater is a solid choice for outdoor spaces needing efficient, low-emission hot water. It fits homes prioritizing environmental compliance and reliable outdoor performance.
Takagi T-H3M Outdoor Natural Gas Heater
Best for: tight outdoor natural gas installations
- Fuel Type
- Natural Gas
- Installation Location
- Outdoor
- Dimensions
- 29.5 x 13.1 x 17.8 inches
- Venting Type
- Condensing
- Weight
- 44 pounds
View on Amazon: Takagi T-H3M Outdoor Natural Gas Heater Affiliate link
This Takagi unit is a condensing natural gas water heater designed for outdoor installation. It measures 29.5 inches high and weighs 44 pounds. The compact 13.1-inch width fits tight spaces. It delivers hot water on demand without a storage tank. This model suits homeowners needing a durable, space-saving solution for outdoor use.
Pros
- Condensing technology for high efficiency
- Compact 13.1-inch width fits tight spaces
- Durable 44-pound build
- Designed specifically for outdoor installation
Cons
- Natural gas fuel type limits placement
- No indoor installation option listed
- Basic white finish offers no color choices
Good fit if
- You need a condensing unit for outdoor use
- You have limited width for installation
- You prefer natural gas over propane
Skip if
- You require indoor installation
- You need propane fuel compatibility
- You want a larger capacity model
Verdict: Takagi T-H3M-OS-N 13.1 in Outdoor Unit fits tight outdoor spaces with its narrow width. It delivers efficient hot water for homes using natural gas.
Takagi Outdoor Propane Tankless Water Heater
Best for: outdoor propane homes needing 8 GPM
- Fuel Type
- Propane
- Flow Rate
- 8 GPM
- Installation Location
- Outdoor
- Dimensions
- 24.9 x 17.8 x 11.3 in
- Venting Type
- Condensing
- Capacity
- 8 Gallon
View on Amazon: Takagi Outdoor Propane Tankless Water Heater Affiliate link
This Takagi unit delivers 8 GPM of hot water using propane fuel. It is designed for outdoor installation and uses condensing technology for high efficiency. The unit measures 24.9 by 17.8 by 11.3 inches and weighs 69 pounds. It meets ultra-low NOx emission standards. You get endless hot water with compact space-saving design and computerized safety features.
Pros
- 8 GPM flow rate
- Condensing high efficiency
- Ultra-low NOx emissions
- Outdoor installation ready
- Propane fuel type
Cons
- Propane only, not natural gas
- Outdoor use only
- No remote control mentioned
Good fit if
- You use propane fuel
- You need 8 GPM capacity
- You have outdoor mounting space
Skip if
- You need natural gas
- You require indoor installation
- You need higher than 8 GPM
Verdict: Takagi T-H3S-OS-P Propane Outdoor Heater suits outdoor propane users needing 8 GPM. It fits homes prioritizing high efficiency and low emissions.
Rheem RTG 9.5 GPM Outdoor Natural Gas Tankless Heater
Best for: outdoor whole-house high flow needs
- Fuel Type
- Natural Gas
- Flow Rate
- 9.5 GPM
- BTU
- 199,900 BTU/hr
- Installation Location
- Outdoor
- Temperature Control
- ±1°F
- Certification
- CSA
View on Amazon: Rheem RTG 9.5 GPM Outdoor Natural Gas Tankless Heater Affiliate link
The Rheem RTG-95XLN is a non-condensing natural gas tankless water heater designed for outdoor use. It delivers 9.5 GPM at a 35°F rise, powered by 199,900 BTUs. The unit features a digital LED panel with ±1°F precision and includes built-in freeze protection. Its non-condensing design allows for simpler venting compared to condensing models. This unit suits large homes needing high flow rates without the complexity of condensing technology.
Pros
- 9.5 GPM flow rate for whole-house use
- Non-condensing design simplifies outdoor installation
- Digital LED control with ±1°F precision
- Built-in freeze protection for outdoor durability
Cons
- Non-condensing technology is less efficient than condensing alternatives
- No WiFi connectivity in this specific model variant
- Requires outdoor installation only
Good fit if
- You need high flow rates for multiple simultaneous showers
- You prefer the simpler venting of non-condensing units
- You are installing the unit in an outdoor location
Skip if
- You require indoor installation capabilities
- You want the highest possible energy efficiency ratings
- You need remote WiFi monitoring and control
Verdict: The Rheem RTG-95XLN Non-Condensing 9.5 GPM is a robust option for outdoor whole-house heating. It delivers consistent high flow without the complexity of condensing venting, making it ideal for large families in mild climates.
Rinnai RU160eN 9 GPM Outdoor Natural Gas
Best for: Outdoor whole-home hot water needs
- Fuel Type
- Natural Gas
- Flow Rate
- 9 GPM
- Installation Location
- Outdoor
- Dimensions
- 33.9 x 14.8 x 22.1 inches
- Venting Type
- Condensing
- Weight
- 71 pounds
View on Amazon: Rinnai RU160eN 9 GPM Outdoor Natural Gas Affiliate link
This Rinnai unit delivers 9 GPM of hot water using natural gas. It is designed for outdoor installation and features condensing technology for high efficiency. The device includes Circ-Logic to pair with an external pump for recirculation. It measures 33.9 by 14.8 by 22.1 inches and weighs 71 pounds. This model suits homes needing steady flow for multiple appliances.
Pros
- 9 GPM flow rate supports up to 6 appliances
- Condensing design provides high energy efficiency
- Circ-Logic compatible with external recirculation pump
- 15-year heat exchanger warranty
Cons
- Requires external pump for recirculation functionality
- Controlr Wi-Fi module sold separately
- Heavier build at 71 pounds
Good fit if
- You need 9 GPM for whole-home use
- You have outdoor space for installation
- You want high efficiency with natural gas
Skip if
- You require indoor installation only
- You need propane fuel type
- You prefer a lighter unit under 70 pounds
Verdict: Rinnai RU160eN 9 GPM Outdoor Natural Gas offers steady 9 GPM flow and condensing efficiency for outdoor use. It fits homes needing multi-appliance support but requires purchasing the recirculation pump and Wi-Fi module separately.
A. O. Smith 10 GPM Outdoor Condensing Tankless Heater
Best for: High flow outdoor natural gas needs
- Fuel Type
- Natural Gas
- Flow Rate
- 10.0 GPM
- BTU
- 199,000 BTU/hr
- Installation Location
- Outdoor
- Dimensions
- 23.6 x 17.8 x 17.8 inches
- Venting Type
- Condensing
View on Amazon: A. O. Smith 10 GPM Outdoor Condensing Tankless Heater Affiliate link
This outdoor natural gas unit delivers 10.0 GPM with 199,000 BTU/hr of heating power. The condensing design achieves a 0.94 UEF. It includes a wall-mounted remote controller for easy temperature adjustment. The commercial-grade copper heat exchanger offers durable heat transfer. This model suits larger homes needing high flow rates in outdoor settings.
Pros
- 10.0 GPM continuous flow rate
- 199,000 BTU/hr heating capacity
- 0.94 Uniform Energy Factor
- Includes wall mount temperature remote
Cons
- Heavier at 59 pounds
- Limited to natural gas fuel
- Outdoor installation only
Good fit if
- You need high flow for multiple bathrooms
- You have an outdoor installation space
- You want a remote temperature controller
Skip if
- You require propane fuel
- You need indoor direct vent
- You prefer a lighter unit
Verdict: A. O. Smith 10 GPM Outdoor Condensing fits homes requiring high capacity hot water in outdoor locations. The copper heat exchanger and remote control add practical value for users needing reliable performance.
Rheem 6.8 GPM Outdoor Condensing Water Heater
Best for: Cold climate outdoor installations with safety needs
- Fuel Type
- Natural Gas
- Flow Rate
- 6.8 GPM
- Installation Location
- Outdoor
- Dimensions
- 28.5 x 9.75 x 27.5 inches
- Venting Type
- Condensing
- Weight
- 77 pounds
View on Amazon: Rheem 6.8 GPM Outdoor Condensing Water Heater Affiliate link
This Rheem unit delivers 6.8 GPM of natural gas hot water for outdoor use. It features condensing technology for high efficiency and includes freeze protection down to -30 degrees. The compact design measures 28.5 by 9.75 by 27.5 inches and weighs 77 pounds. It also detects water and gas leaks to shut down safely. You should consider this if you need reliable outdoor performance in cold climates.
Pros
- 6.8 GPM flow rate for natural gas
- Condensing technology for high efficiency
- Freeze protection down to -30 degrees
- Water and gas leak detection system
Cons
- Lower flow rate than the 9.5 GPM Rheem RTG Series
- Heavier at 77 pounds than many competitors
- No remote control or app connectivity mentioned
Good fit if
- You need freeze protection for outdoor winter use
- You want leak detection safety features
- You prefer a compact outdoor installation
Skip if
- You require a flow rate above 7 GPM
- You need indoor installation capabilities
- You want smart home integration features
Verdict: Rheem RTGH-68XLN-2 6.8 GPM Outdoor Unit suits homes in cold climates needing reliable outdoor heating with safety features, though it lacks the higher flow rates of other options.
Specifications side by side
| Spec | Takagi Outdoor 8 GPM Natural Gas Water Heater | Takagi T-H3M Outdoor Natural Gas Heater | Takagi Outdoor Propane Tankless Water Heater | Rheem RTG 9.5 GPM Outdoor Natural Gas Tankless Heater | Rinnai RU160eN 9 GPM Outdoor Natural Gas | A. O. Smith 10 GPM Outdoor Condensing Tankless Heater | Rheem 6.8 GPM Outdoor Condensing Water Heater |
|---|---|---|---|---|---|---|---|
| Fuel Type | Natural Gas | Natural Gas | Propane | Natural Gas | Natural Gas | Natural Gas | Natural Gas |
| Flow Rate | 8 GPM | not stated | 8 GPM | 9.5 GPM | 9 GPM | 10.0 GPM | 6.8 GPM |
| BTU | not stated | not stated | not stated | 199,900 BTU/hr | not stated | 199,000 BTU/hr | not stated |
| Installation Location | Outdoor | Outdoor | Outdoor | Outdoor | Outdoor | Outdoor | Outdoor |
| Temperature Control | not stated | not stated | not stated | ±1°F | not stated | not stated | not stated |
| Certification | not stated | not stated | not stated | CSA | not stated | not stated | not stated |
| Dimensions | 24.9 x 17.8 x 11.3 inches | 29.5 x 13.1 x 17.8 inches | 24.9 x 17.8 x 11.3 in | 20.8 x 13.5 x 9.4 inches | 33.9 x 14.8 x 22.1 inches | 23.6 x 17.8 x 17.8 inches | 28.5 x 9.75 x 27.5 inches |
| Venting Type | Condensing | Condensing | Condensing | Non-Condensing | Condensing | Condensing | Condensing |
| Capacity | 8 Gallon | not stated | 8 Gallon | not stated | not stated | not stated | not stated |
| Features | not stated | not stated | not stated | WiFi | not stated | not stated | not stated |
| Weight | not stated | 44 pounds | 69 pounds | 39.3 pounds | 71 pounds | 59 pounds | 77 pounds |
| Size | Medium | not stated | Medium | 9.5 GPM (No WiFi) | 9 GPM | not stated | not stated |
| Color | White | White | No Finish | Gray | Outdoor Installation | White | Gray |
| Model | T-H3S-OS-N | TH3MOSNG | T-H3S-OS-P | RTG-95XLN-3 | RU160eN | ATO-540H-N 100 | RTGH-68XLN-2 |
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Frequently asked questions
Is there a propane version of the Takagi T-H3S-OS-N?
Yes, the Takagi T-H3S-OS-P serves as the propane alternative. It maintains the same 8 GPM capacity and condensing venting technology. The unit shares identical dimensions with the natural gas model, measuring 17.8 inches in width and 24.9 inches in height. This option suits outdoor homes that prefer propane fuel for their hot water needs.
What is the narrowest outdoor tankless water heater available?
The Takagi T-H3M-OS-N offers the narrowest profile at 13.1 inches wide. This compact design fits tight outdoor spaces better than wider units. It uses natural gas and features condensing venting for high efficiency. The unit weighs 44 pounds and stands 29.5 inches tall, providing a slim footprint for constrained installations.
Which alternative does not require condensing venting?
The Rheem RTG-95XLN-3 is a non-condensing option for outdoor use. It delivers a high flow rate of 9.5 GPM using natural gas. This model avoids the complexity of condensing venting systems. It also includes WiFi connectivity for remote monitoring. The unit weighs 39.3 pounds and measures 13.5 inches in width.
Can I get 10 GPM from an outdoor condensing unit?
The A. O. Smith ATO-540H-N 100 provides 10 GPM in an outdoor condensing setup. It operates at 199,000 BTU with a copper heat exchanger. The unit includes a remote control for convenience. It measures 17.8 inches wide and weighs 59 pounds, making it a robust choice for high-flow outdoor natural gas requirements.
Is there a 9 GPM condensing option with WiFi?
The Rinnai RU160eN delivers 9 GPM with condensing efficiency for outdoor use. It supports multi-appliance hot water demand. Note that WiFi modules and recirculation pumps are sold separately. The unit is larger, measuring 22.1 inches in length and weighing 71 pounds. It requires separate purchases for smart connectivity features.
Which unit is best for cold climates?
The Rheem RTGH-68XLN-2 is designed for cold climate outdoor installations. It provides 6.8 GPM with condensing venting and built-in safety features. The unit is wider at 27.5 inches but only 9.75 inches deep. It weighs 77 pounds. This model prioritizes reliability in freezing conditions over higher flow rates.