Takagi or A. O. Smith? Tankless Water Heaters Compared in 2026
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Choosing a takagi vs a o smith tankless water heater requires looking at how each unit handles your hot water needs. Both brands offer outdoor, condensing natural gas models designed for efficiency and endless supply. The main difference lies in capacity and size. The Takagi delivers 8 GPM in a slimmer profile, while the A. O. Smith provides 10 GPM with higher BTU output. This affects flow rates and physical footprint for your installation.
Key differences
| Aspect | Takagi Outdoor 8 GPM Natural Gas Water Heater | A. O. Smith 10 GPM Outdoor Condensing Tankless Heater |
|---|---|---|
| Flow Rate | 8 GPM | 10 GPM |
| BTU | not listed | 199,000 BTU/hr |
| Dimensions | 24.9 x 17.8 x 11.3 inches | 23.6 x 17.8 x 17.8 inches |
| Weight | not listed | 59 pounds |
Which one should you choose?
Choose Takagi Outdoor 8 GPM Natural Gas Water Heater if
- You need a narrower unit for tight outdoor spaces.
- Your household usage requires up to 8 GPM of simultaneous flow.
- You prefer a model with ultra-low NOx emissions certification.
Choose A. O. Smith 10 GPM Outdoor Condensing Tankless Heater if
- You need higher flow rates for multiple bathrooms.
- You want a commercial-grade copper heat exchanger for better heat transfer.
- You require a wall-mount temperature remote controller included.
Verdict: Choose the Takagi if space is tight and 8 GPM meets your needs. Select the A. O. Smith if you need higher flow and advanced diagnostics. Both are efficient outdoor options.
Takagi vs A. O. Smith Comparison
Flow Rate Capacity
The A. O. Smith model delivers a continuous flow rate of up to 10.0 GPM. This higher capacity supports a 4-bath home in southern climates or a 3-bath home in northern regions. The Takagi unit provides 8 GPM. While sufficient for many households, it handles fewer simultaneous fixtures. If you need more hot water for multiple showers running at once, the A. O. Smith unit offers greater volume. The Takagi is better suited for smaller households or homes with lower simultaneous demand.
Heating Power
The A. O. Smith heater operates at a maximum of 199,000 BTU/hr. This high input allows it to raise water temperature significantly even with large flow rates. The Takagi specifications do not list a BTU rating in the provided data. Without this figure, it is harder to gauge its heating intensity relative to the A. O. Smith. Generally, higher BTUs support higher flow rates. The A. O. Smith unit clearly has the advantage in stated heating power.
Physical Dimensions
Both units are designed for outdoor installation and share the same width of 17.8 inches. The Takagi is taller at 24.9 inches but narrower in depth at 11.3 inches. The A. O. Smith is shorter at 23.6 inches but deeper at 17.8 inches. The Takagi has a more vertical footprint, which might fit better in narrow vertical spaces. The A. O. Smith is more compact in height but requires more depth. Choose based on your available wall space dimensions.
Heat Exchanger Build
The A. O. Smith unit features a commercial-grade copper heat exchanger. This material provides 25 times better heat transfer compared to steel. It also comes with a 15-year limited warranty on the heat exchanger for residential use. The Takagi data does not specify the heat exchanger material or warranty length. Copper generally offers superior durability and efficiency in heat exchange. The A. O. Smith provides more specific details on build quality and long-term protection.
Control Features
The A. O. Smith includes a wall mount temperature remote controller. This allows you to adjust settings from a distance. It also features advanced diagnostics for easier troubleshooting. The Takagi lists computerized safety features but does not mention a remote controller or diagnostic display. If you want to monitor or change water temperature without approaching the unit, the A. O. Smith offers more convenient control options.
Which tankless heater fits your home
Large family needing high flow
The A. O. Smith unit delivers 10.0 GPM, supporting up to four bathrooms. Its 199,000 BTU output ensures consistent hot water for multiple simultaneous uses. The commercial-grade copper heat exchanger provides superior heat transfer. This higher capacity handles heavy household demand more effectively than the smaller Takagi model.
Compact installation space available
The Takagi model measures 24.9 x 17.8 x 11.3 inches. Its narrower depth of 11.3 inches fits tighter wall spaces. It provides 8 GPM of hot water. This compact footprint is ideal for smaller utility areas or tighter outdoor enclosures where the deeper A. O. Smith unit will not fit.
Ultra-low emissions compliance needed
The Takagi T-H3S-OS-N satisfies the 2012 SCAQMD Rule 1146.2 for ultra-low NOx emissions. This specific compliance is crucial for certain regulated regions. It offers 8 GPM flow with computerized safety features. Choose this model if local air quality regulations require this specific emission standard for outdoor gas units.
The products compared
Takagi Outdoor 8 GPM Natural Gas Water Heater
Best for: outdoor natural gas needs
- 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 gallons per minute of hot water using natural gas. It is designed for outdoor installation and features condensing technology for high efficiency. The compact footprint measures 24.9 by 17.8 by 11.3 inches. It meets strict emission standards for ultra-low NOx output. You get endless hot water without a standing pilot light. This model suits outdoor spaces where venting and weather resistance matter.
Pros
- 8 GPM flow rate for steady hot water
- Condensing design for high energy efficiency
- Ultra-low NOx emissions compliance
- No pilot light reduces standby loss
Cons
- Limited to natural gas fuel type
- Outdoor installation only
- Compact size may limit peak demand handling
Good fit if
- You need an outdoor water heater
- You require high efficiency condensing technology
- You want ultra-low emission compliance
Skip if
- You need indoor installation options
- You use propane fuel
- You need higher than 8 GPM capacity
Verdict: Takagi T-H3S-OS-N 8 GPM Outdoor Gas Heater delivers reliable outdoor performance with high efficiency. It fits outdoor spaces needing strict emission standards and steady hot water flow.
A. O. Smith 10 GPM Outdoor Condensing Tankless Heater
Best for: Outdoor 3-4 bath homes
- 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 of hot water at 199,000 BTU. It uses condensing technology to reach a high Uniform Energy Factor of .94. The commercial-grade copper heat exchanger offers superior heat transfer. It includes a wall mount temperature remote controller for easy adjustment. This model is designed for outdoor installation with flexible direct venting options.
Pros
- 10.0 GPM flow rate for multiple bathrooms
- 199,000 BTU/hr heating capacity
- Commercial-grade copper heat exchanger
- Includes wall mount temperature remote controller
- Energy Star certified with .94 UEF
Cons
- Outdoor-only installation location
- Heavier at 59 pounds
- Requires professional installation
Good fit if
- You need a high-flow unit for a 3 to 4 bath home
- You have an outdoor space for direct venting
- You want a copper heat exchanger for durability
Skip if
- You require indoor installation
- You prefer propane fuel type
- You need a compact unit under 50 pounds
Verdict: A. O. Smith 10 GPM Outdoor Gas Heater suits homes needing high capacity hot water outdoors. Its copper heat exchanger and included remote controller make it a solid choice for large families.
Specifications side by side
| Spec | Takagi Outdoor 8 GPM Natural Gas Water Heater | A. O. Smith 10 GPM Outdoor Condensing Tankless Heater |
|---|---|---|
| Fuel Type | Natural Gas | Natural Gas |
| Flow Rate | 8 GPM | 10.0 GPM |
| BTU | not stated | 199,000 BTU/hr |
| Installation Location | Outdoor | Outdoor |
| Dimensions | 24.9 x 17.8 x 11.3 inches | 23.6 x 17.8 x 17.8 inches |
| Venting Type | Condensing | Condensing |
| Capacity | 8 Gallon | not stated |
| Weight | not stated | 59 pounds |
| Size | Medium | not stated |
| Color | White | White |
| Model | T-H3S-OS-N | ATO-540H-N 100 |
Frequently asked questions
Which tankless water heater has a higher flow rate?
The A. O. Smith model delivers a higher flow rate. It provides up to 10.0 gallons per minute. The Takagi unit offers 8 gallons per minute. This difference supports more simultaneous uses in larger homes. You should choose the A. O. Smith if you need maximum capacity for multiple bathrooms.
Do both brands offer outdoor condensing units?
Yes, both brands provide outdoor condensing models. The Takagi T-H3S-OS-N is designed for outdoor natural gas use. The A. O. Smith ATO-540H-N is also built for outdoor installation. Both units utilize condensing venting technology. This feature helps them meet strict emission standards while saving energy.
Which unit is physically smaller?
The Takagi heater has a more compact footprint. Its dimensions are 11.3 inches in length. The A. O. Smith unit is 17.8 inches long. Both units share the same width of 17.8 inches. If space is limited in your outdoor area, the Takagi model fits more easily.
What type of fuel do these heaters use?
Both heaters run on natural gas. This fuel type is common for outdoor installations. It provides consistent heating performance. You will need a natural gas line for either unit. Both models are not designed for propane or electric power sources.
Is a remote controller included with the A. O. Smith?
Yes, the A. O. Smith unit includes a remote controller. This allows you to adjust settings from a distance. The Takagi product data does not mention a remote. You may need to access the unit directly for adjustments. The remote adds convenience for outdoor placement.
Which brand is better for a 3-4 bath home?
The A. O. Smith is better for larger homes. Its 10.0 GPM flow rate supports up to four bathrooms. The Takagi 8 GPM unit is suitable for smaller households. You should select the A. O. Smith if you have high simultaneous water demands. It handles multiple showers more effectively.
What is the BTU output of the A. O. Smith?
The A. O. Smith heater has a 199,000 BTU output. This high output ensures rapid water heating. The Takagi product data does not list its BTU rating. Higher BTUs generally mean faster recovery times. This spec helps maintain temperature during heavy usage.
Are both units white in color?
Yes, both units are white. The Takagi T-H3S-OS-N is white. The A. O. Smith ATO-540H-N is also white. This color choice blends with most exterior walls. It provides a clean, uniform look for outdoor installations. You do not need to worry about mismatched finishes.