6 Best Alternatives to the Takagi T-H3M Outdoor Natural Gas (2026)
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You are looking for takagi t h3m outdoor natural gas alternatives because the original unit has specific limitations. The Takagi T-H3M Outdoor Natural Gas Heater is a compact, condensing unit designed for outdoor use. It measures 13.1 inches wide and 29.5 inches tall. This small footprint makes it ideal for tight outdoor spaces. However, its 44-pound weight and fixed natural gas fuel type may not suit every home. Some buyers need higher flow rates, different venting options, or indoor placement capabilities. The original model does not offer WiFi connectivity or high-volume output for large households. These gaps explain why you might want to explore other options. We selected alternatives based on overlapping specifications with the original. Each product shares key traits like outdoor installation, natural gas fuel, or condensing technology. This ensures that any replacement fits your existing infrastructure. The list includes 6 units that vary in size, flow rate, and features. You can find models with higher BTU inputs, non-condensing venting, or indoor suitability. These choices cover a range of needs while maintaining compatibility with your gas supply. The following sections detail how each spec compares to the Takagi T-H3M. You will see clear differences in dimensions, weight, and operational features. This guide helps you choose the right unit for your specific situation.
How each alternative compares
Takagi Outdoor 8 GPM Natural Gas Water Heater
The Takagi T-H3S Outdoor 8 GPM shares the same natural gas fuel and condensing venting technology as the T-H3M. It offers a higher flow rate, which helps when multiple fixtures run at once. However, it is wider at 17.8 inches compared to the T-H3M’s 13.1 inches. You gain efficiency and capacity but lose some compactness. This unit suits homes needing strict emissions compliance. It is a better choice if you prioritize environmental standards and higher hot water output over the smallest possible footprint. The trade-off is a larger width that may not fit in tight spaces.
Rheem RTG 9.5 GPM Outdoor Natural Gas Tankless Heater
The Rheem RTG 9.5 GPM provides a significantly higher flow rate of 9.5 gallons per minute. It uses non-condensing venting, which simplifies installation by removing the need for complex condensing exhaust systems. It is also lighter at 39.3 pounds and shorter at 20.8 inches tall. You get more hot water and easier venting, but you sacrifice the higher efficiency of condensing technology. This model fits large families needing high-volume hot water. It is ideal if you want to avoid condensing vent requirements. The WiFi feature adds remote control, which the T-H3M does not list. Choose this for maximum flow and simple outdoor setup.
Rinnai RU160eN 9 GPM Outdoor Natural Gas
The Rinnai RU160eN delivers 9 GPM of hot water, exceeding the T-H3M’s capacity. It uses condensing venting like the T-H3M, ensuring high efficiency. However, it is much larger, measuring 33.9 inches tall and 22.1 inches long. It also weighs 71 pounds, making it heavier than the T-H3M. You gain substantial flow for whole-home supply but require more wall space and structural support. This unit suits large households with high hot water demands. It is a strong option if you prioritize volume over compact size. The trade-off is a significant increase in physical dimensions and weight compared to the smaller Takagi model.
A. O. Smith 10 GPM Outdoor Condensing Tankless Heater
The A. O. Smith 10 GPM offers the highest flow rate on this list at 10 gallons per minute. It uses condensing venting and delivers 199,000 BTU of power. It is wider at 17.8 inches and heavier at 59 pounds than the T-H3M. You get maximum hot water capacity for large homes, such as those with four bathrooms. However, you sacrifice the compact footprint of the T-H3M. This unit fits large households in warm regions needing high flow. It is the best choice if volume is your primary concern. The trade-off is a larger, heavier unit that requires more installation space compared to the slim Takagi design.
Rheem 6.8 GPM Outdoor Condensing Water Heater
The Rheem 6.8 GPM Outdoor Condensing Heater has a lower flow rate than the T-H3M. It shares the condensing venting type and natural gas fuel. It is narrower at 9.75 inches wide but much deeper at 27.5 inches long. It also weighs 77 pounds, making it the heaviest option here. You gain a leak detection feature and freeze resistance, which are valuable in cold climates. However, you lose flow speed and compactness. This unit suits homes in cold regions prioritizing safety. It is a solid choice if you need leak detection over maximum flow. The trade-off is a deeper, heavier design with lower output than the Takagi.
Noritz 6.6 GPM Indoor Natural Gas Tankless Heater
The Noritz NRC66DVNG is designed for indoor installation, unlike the outdoor T-H3M. It has a lower flow rate of 6.6 GPM. It uses condensing venting with PVC, which is simpler for indoor setups. It is lighter at 38 pounds and shorter at 23.6 inches tall. You gain the ability to install it indoors with standard PVC venting. However, you lose outdoor durability and higher flow capacity. This unit fits indoor spaces where PVC venting is allowed. It is not suitable for outdoor use. The trade-off is significantly lower flow and indoor-only placement, making it a different category of heater compared to the outdoor Takagi model.
Quick picks
Our 7 picks
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
The Takagi T-H3M-OS-N is a condensing outdoor tankless water heater designed for natural gas. It weighs 44 pounds and measures 29.5 x 13.1 x 17.8 inches. This compact unit fits well in tight outdoor spaces. It delivers reliable on-demand hot water without the bulk of a traditional tank. You get efficient heating with a smaller footprint. It is a solid choice for homeowners needing a durable outdoor solution.
Pros
- Condensing technology for high efficiency
- Compact dimensions: 29.5 x 13.1 x 17.8 inches
- Lightweight at 44 pounds
- Designed specifically for outdoor installation
Cons
- Limited to natural gas fuel type
- No indoor installation option
- Single fuel compatibility restricts flexibility
Good fit if
- You need a compact unit for a tight outdoor space
- You have a natural gas supply available
- You want a durable outdoor-specific heater
Skip if
- You require propane or dual-fuel capability
- You need an indoor-rated unit
- You prefer a non-condensing model
Verdict: Takagi T-H3M-OS-N Outdoor Natural Gas Heater is a compact, efficient choice for outdoor natural gas setups. It fits well in tight spaces where size matters.
Takagi Outdoor 8 GPM Natural Gas Water Heater
Best for: outdoor homes needing strict emissions compliance
- 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
The Takagi T-H3S-OS-N is an outdoor condensing natural gas water heater delivering 8 GPM. It measures 24.9 by 17.8 by 11.3 inches. The unit meets 2012 SCAQMD Rule 1146.2 for ultra-low NOx emissions. It has no pilot light. This model suits homes needing steady hot water in outdoor settings while prioritizing energy efficiency and compact installation.
Pros
- 8 GPM flow rate for natural gas
- Condensing technology for high efficiency
- Meets SCAQMD Rule 1146.2 ultra-low NOx standards
- No pilot light reduces standby loss
Cons
- 8 GPM is lower than the 9.5 GPM Rheem RTG Series
- Outdoor-only installation limits placement options
- Lacks remote control or app connectivity
Good fit if
- You need an outdoor unit for natural gas
- You require compliance with strict NOx emissions rules
- You want a compact condensing heater
Skip if
- You need more than 8 GPM flow
- You plan to install the unit indoors
- You require digital remote control features
Verdict: Takagi T-H3S Outdoor 8 GPM delivers reliable outdoor hot water with strict emissions compliance. It fits buyers who prioritize efficiency and environmental standards over maximum flow rate.
Rheem RTG 9.5 GPM Outdoor Natural Gas Tankless Heater
Best for: High-flow outdoor installations without condensing vents
- 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-3 delivers 9.5 GPM at a 35°F rise with 199,900 BTUs. It uses non-condensing technology, eliminating complex venting for outdoor use. The unit features a digital LED panel with ±1°F precision and built-in freeze protection. It suits large homes needing high flow rates without the bulk of condensing systems.
Pros
- 9.5 GPM flow rate supports 3-4 simultaneous showers
- Non-condensing design simplifies outdoor installation
- Digital LED control with ±1°F temperature precision
- Built-in freeze and flame failure protection
Cons
- Lower efficiency (0.82 UEF) compared to condensing models
- No WiFi connectivity in this specific variant
- Heavier at 39.3 pounds than compact alternatives
Good fit if
- You need maximum hot water flow for a large household
- You prefer simpler non-condensing venting for outdoor installation
- You want precise temperature control via digital display
Skip if
- You require the highest possible energy efficiency ratings
- You need smart home integration or WiFi control
- You are installing in a space with strict weight limits
Verdict: Rheem RTG 9.5 GPM Non-Condensing provides robust flow for large families who prioritize simple outdoor installation over maximum efficiency. It fits homes needing high volume hot water without complex venting requirements.
Rinnai RU160eN 9 GPM Outdoor Natural Gas
Best for: High-flow 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
The Rinnai RU160eN delivers 9 GPM of hot water for outdoor use. It heats natural gas efficiently with a 0.95 Uniform Energy Factor. The unit measures 33.9 by 14.8 by 22.1 inches and weighs 71 pounds. You can pair it with an external pump for recirculation. This model suits homes needing high flow rates without the bulk of a tank.
Pros
- 9 GPM flow rate supports up to 6 appliances
- 0.95 Uniform Energy Factor for efficiency
- 15-year heat exchanger warranty
- Compact outdoor design saves space
Cons
- Wifi monitoring module is not included
- Professional installation is required
- Heavier at 71 pounds than some competitors
Good fit if
- You need high flow for multiple simultaneous uses
- You have an outdoor installation space
- You want a condensing unit for efficiency
Skip if
- You prefer indoor installation only
- You want built-in wifi without extra parts
- You need a propane fuel source
Verdict: Rinnai RU160eN 9 GPM Outdoor Natural Gas fits large households requiring reliable, high-volume hot water outdoors. Its condensing efficiency and durable heat exchanger make it a strong option for whole-home supply.
A. O. Smith 10 GPM Outdoor Condensing Tankless Heater
Best for: large homes needing high flow
- 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 input. It uses condensing technology to reach a 0.94 UEF. The copper heat exchanger offers strong heat transfer. You get a wall-mount temperature remote and flexible direct venting up to 100 feet. It fits homes with up to four bathrooms in southern climates.
Pros
- 10.0 GPM continuous flow rate
- 199,000 BTU/hr input capacity
- 0.94 Uniform Energy Factor rating
- Includes wall-mount temperature remote
- Venting up to 100 feet
Cons
- Heavier at 59 pounds
- Requires professional installation
- Limited to natural gas fuel
Good fit if
- You need high flow for multiple bathrooms
- You want a condensing outdoor unit
- You prefer copper heat exchangers
Skip if
- You need propane fuel
- You want indoor-only installation
- You prefer smaller dimensions
Verdict: A. O. Smith 10 GPM Outdoor Gas suits large households needing high capacity. It works well for four-bathroom homes in warm regions.
Rheem 6.8 GPM Outdoor Condensing Water Heater
Best for: cold climates needing leak detection
- 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
The Rheem Prestige RTGH-68XLN-2 is a condensing outdoor water heater designed for natural gas. It delivers 6.8 GPM with freeze protection down to -30 degrees. Its compact gray body measures 28.5 x 9.75 x 27.5 inches and weighs 77 pounds. This unit includes water and gas leak detection to shut down the system if a problem occurs. It suits households needing reliable outdoor hot water with safety features.
Pros
- 6.8 GPM flow rate for natural gas
- Freeze protection down to -30 degrees
- Water and gas leak detection system
- Condensing design for high efficiency
- Compact outdoor installation footprint
Cons
- Lower flow rate than 9 GPM competitors
- Heavier at 77 pounds
- Smaller capacity than 9.5 GPM models
Good fit if
- You need freeze protection for cold climates
- You want leak detection safety features
- You have limited outdoor space
Skip if
- You require more than 6.8 GPM
- You prefer indoor installation only
- You need a lighter unit under 70 pounds
Verdict: Rheem 6.8 GPM Outdoor Natural Gas Heater fits homes prioritizing safety and freeze resistance over maximum flow speed. It is a solid choice for cold regions where leak detection matters.
Noritz 6.6 GPM Indoor Natural Gas Tankless Heater
Best for: indoor installations with PVC venting
- Fuel Type
- Natural Gas
- Flow Rate
- 6.6 GPM
- Installation Location
- Indoor
- Venting Type
- Condensing
- Dimensions
- 6.7 × 13.8 × 23.6 inches
- Weight
- 38 pounds
View on Amazon: Noritz 6.6 GPM Indoor Natural Gas Tankless Heater Affiliate link
The Noritz NRC66DVNG is a condensing tankless water heater designed for indoor installation. It delivers 6.6 GPM of hot water using natural gas. The unit measures 13.8 inches wide and weighs 38 pounds. It includes a remote thermostat and a 6-foot power cord. You can vent it with standard Schedule 40 PVC pipe. This compact model suits homes where outdoor units are not feasible or permitted.
Pros
- 6.6 GPM flow rate
- Includes remote thermostat
- PVC venting compatible
- Condensing high efficiency
Cons
- Indoor installation only
- Lower 6.6 GPM flow rate
- Heavier 38-pound build
Good fit if
- You need an indoor unit
- You prefer PVC venting
- You want remote control
Skip if
- You require outdoor placement
- You need higher flow rates
- You want lighter weight
Verdict: Noritz NRC66DVNG 6.6 GPM Indoor Heater fits indoor spaces where PVC venting is allowed and a remote thermostat is useful. It is not suitable for outdoor use or high-demand households.
Specifications side by side
| Spec | Takagi T-H3M Outdoor Natural Gas Heater | Takagi Outdoor 8 GPM Natural Gas 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 | Noritz 6.6 GPM Indoor Natural Gas Tankless Heater |
|---|---|---|---|---|---|---|---|
| Fuel Type | Natural Gas | Natural Gas | Natural Gas | Natural Gas | Natural Gas | Natural Gas | Natural Gas |
| Flow Rate | not stated | 8 GPM | 9.5 GPM | 9 GPM | 10.0 GPM | 6.8 GPM | 6.6 GPM |
| BTU | not stated | not stated | 199,900 BTU/hr | not stated | 199,000 BTU/hr | not stated | not stated |
| Installation Location | Outdoor | Outdoor | Outdoor | Outdoor | Outdoor | Outdoor | Indoor |
| Temperature Control | not stated | not stated | ±1°F | not stated | not stated | not stated | not stated |
| Certification | not stated | not stated | CSA | not stated | not stated | not stated | not stated |
| Dimensions | 29.5 x 13.1 x 17.8 inches | 24.9 x 17.8 x 11.3 inches | 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 | not stated |
| Venting Type | Condensing | Condensing | Non-Condensing | Condensing | Condensing | Condensing | Condensing |
| Capacity | not stated | 8 Gallon | not stated | not stated | not stated | not stated | not stated |
| Features | not stated | not stated | WiFi | not stated | not stated | not stated | not stated |
| Weight | 44 pounds | not stated | 39.3 pounds | 71 pounds | 59 pounds | 77 pounds | 38 pounds |
| Color | White | White | Gray | Outdoor Installation | White | Gray | White |
| Model | TH3MOSNG | T-H3S-OS-N | RTG-95XLN-3 | RU160eN | ATO-540H-N 100 | RTGH-68XLN-2 | NRC661-DV-NG |
| Size | not stated | Medium | 9.5 GPM (No WiFi) | 9 GPM | not stated | not stated | 13.8 inches (W) x 23.6 inches (H) x 10 inches (D) |
If you also outfit an outdoor kitchen, you can compare cuisinart outdoor gas grill alternatives by burner specs.
Frequently asked questions
What is the smallest outdoor natural gas water heater available?
The Takagi T-H3M Outdoor Natural Gas Heater is the most compact option listed. It measures 13.1 inches wide and 17.8 inches long. This small footprint makes it ideal for tight outdoor spaces where size matters. It weighs only 44 pounds, making it lighter than most competitors.
Which outdoor heater offers the highest flow rate?
The A. O. Smith 10 GPM Outdoor Condensing Tankless Heater provides the highest flow rate at 10 gallons per minute. It is designed for large homes needing high capacity. This unit delivers robust performance for four-bathroom households in warm regions. It uses natural gas and condensing venting technology.
Are there non-condensing outdoor natural gas heaters on this list?
Yes, the Rheem RTG 9.5 GPM Outdoor Natural Gas Tankless Heater is non-condensing. It provides 9.5 GPM of hot water without complex venting requirements. This model suits high-flow outdoor installations where simple setup is preferred over maximum efficiency. It includes WiFi connectivity for remote monitoring.
Which outdoor unit is best for cold climates?
The Rheem 6.8 GPM Outdoor Condensing Water Heater is suited for cold climates. It prioritizes safety and freeze resistance over maximum flow speed. This unit features leak detection, which is valuable in regions where freezing temperatures pose a risk. It weighs 77 pounds and uses natural gas.
Can I use an indoor tankless heater outdoors instead?
No, the Noritz 6.6 GPM Indoor Natural Gas Tankless Heater is not suitable for outdoor use. It is designed for indoor installations where PVC venting is allowed. Using it outdoors could damage the unit. For outdoor needs, choose a model explicitly rated for outdoor installation like the Takagi or Rheem options.
Which heater has the highest BTU output?
The A. O. Smith 10 GPM Outdoor Condensing Tankless Heater has the highest BTU output at 199,000 BTU. This high output supports its 10 GPM flow rate. It is ideal for large households requiring significant hot water volume. The unit measures 17.8 inches wide and weighs 59 pounds.
Is there a premium outdoor option with strict emissions compliance?
The Takagi Outdoor 8 GPM Natural Gas Water Heater is the premium choice for strict emissions compliance. It fits buyers who prioritize efficiency and environmental standards. It uses condensing venting and natural gas. The unit is 17.8 inches wide and 24.9 inches tall, offering a medium size profile.