A. O. Smith Tankless Water Heater Natural Alternatives: 6 Similar Picks Compared
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If you are researching a o smith tankless water heater natural alternatives, you likely value the high efficiency and robust flow of the original model. The A. O. Smith unit delivers up to 10.0 GPM with 199,000 BTUs, making it ideal for large outdoor installations. Its condensing technology and copper heat exchanger provide stable temperatures and strong durability for multi-bath households. However, you might prefer a different footprint, a lower flow rate, or a more compact design for tighter spaces. Some buyers also seek options that prioritize specific safety features or simpler venting configurations without sacrificing performance.
This guide compares 6 similar picks that share key specifications with the A. O. Smith model. We selected these alternatives because their attributes overlap with the original, including natural gas fuel type and outdoor installation suitability. Each option offers distinct trade-offs in flow rate, physical dimensions, and venting requirements. You can review the published specs to find a unit that better matches your home’s layout and hot water demands. Whether you need higher capacity for a large family or a more compact unit for a small patio, these comparisons help you identify the right technical fit.
Our top pick: A. O. Smith 10 GPM Outdoor Condensing Tankless Heater.
How these units compare to the A.O. Smith
Camplux Outdoor 8.4 GPM Natural Gas Water Heater
The Camplux WA686M-NG matches the A. O. Smith’s 199,000 BTU output but offers a lower 8.4 GPM flow rate. It is significantly lighter at 39 pounds and narrower, measuring 6.5 inches wide versus the A. O. Smith’s 17.8 inches. This compact footprint suits tight outdoor spots where space is limited. You get the same high heat output for large families, but with reduced simultaneous shower capacity. The trade-off is less flow for easier mounting. Choose this if you need high BTUs in a smaller, lighter package for outdoor use.
Rinnai RU160eN 9 GPM Outdoor Natural Gas
The Rinnai RU160eN provides 9 GPM, slightly less than the A. O. Smith’s 10 GPM, but maintains similar high efficiency. It is taller at 33.9 inches and heavier at 71 pounds, requiring more vertical space. Both units are outdoor condensing models for natural gas. The Rinnai offers a robust flow for large households but demands more installation height. If you prefer a taller, heavier unit with strong performance for multiple bathrooms, this is a solid alternative. It gives up one GPM for a different physical profile.
Takagi Outdoor 8 GPM Natural Gas Water Heater
The Takagi T-H3S-OS-N delivers 8 GPM, which is lower than the A. O. Smith’s 10 GPM. It is also narrower at 11.3 inches deep, making it more compact for wall mounting. Both are outdoor condensing natural gas heaters. The Takagi sacrifices flow rate for a smaller depth, which may help in constrained outdoor areas. You get efficient heating but less simultaneous water availability. Pick this model if space depth is your primary constraint and you can accept lower peak flow for a slimmer installation profile.
Rheem 6.8 GPM Outdoor Condensing Water Heater
The Rheem RTGH-68XLN-2 offers 6.8 GPM, significantly lower than the A. O. Smith’s 10 GPM. It is wider at 27.5 inches but narrower in depth at 9.75 inches. Both are outdoor condensing natural gas units. The Rheem trades high flow for a wider, shallower footprint. This suits moderate hot water needs where simultaneous multi-bathroom use is not critical. You lose substantial flow capacity but gain a different mounting dimension. Choose this if you prioritize a shallow depth over maximum hot water output for large households.
Takagi T-H3M Outdoor Natural Gas Heater
The Takagi T-H3M is a smaller outdoor condensing unit with a lower flow rate than the A. O. Smith’s 10 GPM. It weighs 44 pounds, lighter than the A. O. Smith’s 59 pounds. Its dimensions are 13.1 inches wide and 29.5 inches tall. This model fits tight outdoor spaces where the larger A. O. Smith unit would not fit. You sacrifice significant flow capacity for a more compact size. It is best for single-fixture use or smaller households. Select this if space constraints are your main concern and high simultaneous flow is not required.
Ranein 8.5 GPM Outdoor Natural Gas Water Heater
The Ranein RHO19K-NG lists 8.5 GPM in its size spec, which is lower than the A. O. Smith’s 10 GPM. It is wider at 15.1 inches and shallower at 15.1 inches deep. Both are outdoor natural gas heaters. The Ranein offers a middle-ground flow rate with a square footprint. You get less peak flow than the A. O. Smith but a different mounting shape. This suits buyers needing high capacity without the depth of the A. O. Smith unit. Pick this if you want strong flow in a compact, square outdoor package.
Quick picks
Our 7 picks
A. O. Smith 10 GPM Outdoor Condensing Tankless Heater
Best for: large homes with 3 to 4 bathrooms
- 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 A. O. Smith unit delivers 10.0 GPM of hot water using 199,000 BTU of natural gas. It uses condensing technology to reach a high 0.94 UEF. The copper heat exchanger offers superior heat transfer. It supports outdoor installation and direct venting up to 100 feet. This model suits homes with three to four bathrooms needing steady flow.
Pros
- 10.0 GPM flow rate supports multiple simultaneous uses
- 0.94 UEF efficiency reduces energy usage
- Copper heat exchanger provides 25x better heat transfer than steel
- Includes wall mount temperature remote controller
- Direct vent design allows up to 100 feet of venting
Cons
- Heavier at 59 pounds than some competitors
- Outdoor installation only
- Professional installation recommended
Good fit if
- You need high flow for 3 to 4 bathrooms
- You want efficient condensing technology
- You have space for outdoor mounting
Skip if
- You require indoor installation
- You need propane fuel
- You prefer a lighter unit under 50 pounds
Verdict: A. O. Smith 10 GPM Outdoor Condensing fits large households needing reliable hot water for multiple bathrooms. Its high efficiency and copper core make it a strong pick for outdoor setups.
Camplux Outdoor 8.4 GPM Natural Gas Water Heater
Best for: outdoor high-flow needs
- Fuel Type
- Natural Gas
- Flow Rate
- Up to 8.4 GPM
- BTU
- 199,000 BTU
- Installation Location
- Outdoor
- Certification
- CSA
- Dimensions
- 22.2 x 6.5 x 6.5 inches
View on Amazon: Camplux Outdoor 8.4 GPM Natural Gas Water Heater Affiliate link
This Camplux unit delivers up to 8.4 GPM of hot water using 199,000 BTUs of natural gas. It maintains temperature fluctuations within ±1°F for steady performance. The compact 22.2-inch height and 39-pound weight make it suitable for outdoor mounting. CSA certification confirms safety standards. It fits most existing vent setups without major modifications.
Pros
- High 8.4 GPM flow rate for whole-house use
- Precise ±1°F temperature stability
- Six built-in safety protections
- CSA certified for quality
Cons
- Outdoor installation only
- No remote control included
- Larger footprint than indoor units
Good fit if
- You need high flow rates outdoors
- You want precise temperature control
- You have existing gas lines outside
Skip if
- You need indoor installation
- You require remote operation
- You want a compact indoor unit
Verdict: Camplux 8.4 GPM Natural Gas Outdoor Heater offers strong flow and safety for outdoor setups. It suits buyers needing high capacity without indoor space constraints.
Rinnai RU160eN 9 GPM Outdoor Natural Gas
Best for: Large households with outdoor installation space
- 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 RU160eN is a condensing natural gas tankless water heater designed for outdoor installation. It delivers 9 GPM of hot water, supporting up to six appliances simultaneously. The unit measures 33.9 x 14.8 x 22.1 inches and weighs 71 pounds. It features Circ-Logic technology for recirculation control and holds an ENERGY STAR qualification with a 0.95 Uniform Energy Factor. It suits homes needing high flow rates in outdoor settings.
Pros
- 9 GPM flow rate supports multiple simultaneous uses
- Condensing design offers high energy efficiency
- Circ-Logic allows scheduled or on-demand recirculation
- ENERGY STAR qualified with 0.95 UEF rating
Cons
- Outdoor installation only limits placement options
- Controlr Wi-Fi module is not included
- 71-pound weight requires sturdy mounting
Good fit if
- You need high flow for a large household
- You have an outdoor space for installation
- You want ENERGY STAR certified efficiency
Skip if
- You require indoor installation capability
- You need built-in Wi-Fi connectivity
- You prefer a lighter unit for easy mounting
Verdict: Rinnai RU160eN 9 GPM Outdoor Natural Gas delivers robust performance for large homes with outdoor space. Its high flow rate and efficiency make it ideal for families needing simultaneous hot water access.
Takagi Outdoor 8 GPM Natural Gas Water Heater
Best for: outdoor high-flow efficiency
- 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 a condensing natural gas unit designed for outdoor installation. It delivers 8 gallons per minute of hot water. The compact size measures 24.9 by 17.8 by 11.3 inches. It meets strict SCAQMD Rule 1146.2 for ultra-low NOx emissions. This model suits you if you need high output in a small footprint.
Pros
- 8 GPM flow rate for multiple simultaneous uses
- Condensing design for high energy efficiency
- Ultra-low NOx emissions compliance
- Compact outdoor dimensions
Cons
- Outdoor installation only
- Requires specific venting for condensing operation
- No pilot light means reliance on electrical power for ignition
Good fit if
- You need 8 GPM for whole-house demand
- You have limited outdoor space for installation
- You live in a strict emissions area
Skip if
- You require indoor installation
- You need a non-condensing unit
- You prefer a larger capacity unit
Verdict: Takagi T-H3S-OS-N 8 GPM Outdoor Natural Gas Heater delivers efficient 8 GPM output in a compact condensing package. It fits outdoor spaces where emissions compliance and space saving matter most.
Rheem 6.8 GPM Outdoor Condensing Water Heater
Best for: Moderate flow outdoor installations with safety focus
- 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 hot water using natural gas. It features condensing technology for high efficiency and includes water and gas leak detection. Designed for outdoor installation, it withstands temperatures down to -30 degrees. The compact footprint saves space compared to traditional tanks. You get reliable performance with built-in safety shut-offs for peace of mind.
Pros
- 6.8 GPM flow rate for steady hot water
- Condensing design for high energy efficiency
- Water and gas leak detection with auto shut-off
- Freeze protection down to -30 degrees
- Compact outdoor footprint
Cons
- Lower flow rate than competitors offering 8.5 to 9 GPM
- Heavier build at 77 pounds
- Outdoor installation only
Good fit if
- You need a compact outdoor unit for a single bathroom or kitchen
- You prioritize leak detection safety features
- You live in a cold climate requiring freeze protection
Skip if
- You require a flow rate above 7 GPM for multiple simultaneous showers
- You need an indoor installation option
- You prefer a lighter unit for easier mounting
Verdict: Rheem RTGH-68XLN-2 Outdoor Tankless suits households with moderate hot water needs who value safety features and compact outdoor placement over maximum flow capacity.
Takagi T-H3M Outdoor Natural Gas Heater
Best for: tight outdoor spaces with single-fixture use
- 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 outdoor tankless water heater powered by natural gas. It measures 29.5 by 13.1 by 17.8 inches and weighs 44 pounds. The compact footprint and white finish fit tight exterior spaces. It delivers hot water on demand without a storage tank. You should choose this if you need a durable, space-saving solution for outdoor installation.
Pros
- Condensing technology for efficiency
- Compact outdoor design
- Natural gas fuel type
- Lightweight 44-pound build
Cons
- Lower flow rate than 8.5 GPM competitors
- No indoor installation option
- Basic exterior finish
Good fit if
- You need an outdoor unit
- You have limited exterior space
- You use natural gas
Skip if
- You require indoor installation
- You need high flow rates
- You prefer propane fuel
Verdict: Takagi T-H3M Outdoor Natural Gas Heater fits tight outdoor spots where space is limited. It works well for single-fixture use but may struggle with multiple simultaneous demands.
Ranein 8.5 GPM Outdoor Natural Gas Water Heater
Best for: High-flow outdoor needs below 2,000 ft
- Fuel Type
- Natural Gas
- Flow Rate
- 8.5 GPM
- BTU
- 190,000 BTU
- Installation Location
- Outdoor
- Dimensions
- 15.1 × 15.1 × 24.3 inches
- Weight
- 44 pounds
View on Amazon: Ranein 8.5 GPM Outdoor Natural Gas Water Heater Affiliate link
The Ranein RHO19K-NG delivers 8.5 GPM at 190,000 BTU for outdoor natural gas use. Its compact 24.3 x 15.1 x 8.1 inch frame suits tight spaces. The unit includes anti-freeze protection and a fan system that adjusts to wind pressure. It supports up to six outlets, making it a strong option for larger households needing high flow rates.
Pros
- 8.5 GPM maximum flow rate
- 190,000 BTU heating capacity
- Anti-freeze protection included
- Wind-adjustable combustion fan
- Compact 24.3-inch height
Cons
- Not recommended for altitudes over 2,000 feet
- Requires manual draining in cold weather if unused
- No remote control or app mentioned
Good fit if
- You need high flow for multiple bathrooms
- You have an outdoor installation space
- You live below 2,000 feet elevation
Skip if
- You live above 2,000 feet elevation
- You require indoor installation
- You want smart home integration
Verdict: Ranein 8.5 GPM Natural Gas Outdoor Heater provides high capacity for large families in mild climates. It fits buyers who prioritize flow rate and outdoor durability over smart features.
Specifications side by side
| Spec | A. O. Smith 10 GPM Outdoor Condensing Tankless Heater | Camplux Outdoor 8.4 GPM Natural Gas Water Heater | Rinnai RU160eN 9 GPM Outdoor Natural Gas | Takagi Outdoor 8 GPM Natural Gas Water Heater | Rheem 6.8 GPM Outdoor Condensing Water Heater | Takagi T-H3M Outdoor Natural Gas Heater | Ranein 8.5 GPM Outdoor Natural Gas Water Heater |
|---|---|---|---|---|---|---|---|
| Fuel Type | Natural Gas | Natural Gas | Natural Gas | Natural Gas | Natural Gas | Natural Gas | Natural Gas |
| Flow Rate | 10.0 GPM | Up to 8.4 GPM | 9 GPM | 8 GPM | 6.8 GPM | not stated | 8.5 GPM |
| BTU | 199,000 BTU/hr | 199,000 BTU | not stated | not stated | not stated | not stated | 190,000 BTU |
| Installation Location | Outdoor | Outdoor | Outdoor | Outdoor | Outdoor | Outdoor | Outdoor |
| Certification | not stated | CSA | not stated | not stated | not stated | not stated | not stated |
| Dimensions | 23.6 x 17.8 x 17.8 inches | 22.2 x 6.5 x 6.5 inches | 33.9 x 14.8 x 22.1 inches | 24.9 x 17.8 x 11.3 inches | 28.5 x 9.75 x 27.5 inches | 29.5 x 13.1 x 17.8 inches | not stated |
| Use | not stated | Whole House | not stated | not stated | not stated | not stated | not stated |
| Venting Type | Condensing | not stated | Condensing | Condensing | Condensing | Condensing | not stated |
| Capacity | not stated | not stated | not stated | 8 Gallon | not stated | not stated | not stated |
| Weight | 59 pounds | 39 pounds | 71 pounds | not stated | 77 pounds | 44 pounds | 44 pounds |
| Color | White | White | Outdoor Installation | White | Gray | White | Gray-NG |
| Model | ATO-540H-N 100 | WA686M-NG | RU160eN | T-H3S-OS-N | RTGH-68XLN-2 | TH3MOSNG | RHO19K-NG |
| Size | not stated | 6.86 GPM-NG | 9 GPM | Medium | not stated | not stated | 8.5 GPM Outdoor |
If you also need drinking water filtration, you can compare specifications for apec water apec tankless ro water alternatives separately.
Frequently asked questions
Which natural gas tankless heater matches the A.O. Smith 10 GPM flow rate?
The Camplux Outdoor 8.4 GPM Natural Gas Water Heater comes closest to that high capacity. While it falls slightly short of the 10 GPM target, its 199,000 BTU output matches the A.O. Smith unit. It weighs only 39 pounds and measures 6.5 inches wide, making it a compact alternative for outdoor setups needing strong flow.
Are there outdoor condensing models similar to the A.O. Smith heater?
Yes, several units use condensing venting for efficiency. The Rinnai RU160eN delivers 9 GPM with condensing technology. The Rheem RTGH-68XLN-2 also features condensing venting and weighs 77 pounds. The Takagi T-H3S-OS-N offers 8 GPM in a condensing package. These options provide efficient outdoor performance comparable to the A.O. Smith model.
What is the lightest natural gas outdoor tankless water heater on this list?
The Camplux Outdoor 8.4 GPM Natural Gas Water Heater is the lightest option at 39 pounds. It is also the narrowest, measuring just 6.5 inches in width and length. This compact design makes it easier to mount in tight outdoor spaces compared to heavier units like the Rheem model, which weighs 77 pounds.
Which unit is best for large homes needing multiple bathrooms?
The A.O. Smith 10 GPM Outdoor Condensing Tankless Heater is rated for large homes with 3 to 4 bathrooms. It delivers 10 GPM with 199,000 BTUs. The Rinnai RU160eN is also suitable for large households, offering 9 GPM. Both units provide the high flow capacity needed for simultaneous hot water use in larger households.
How wide is the Camplux 8.4 GPM unit compared to the A.O. Smith?
The Camplux WA686M-NG is significantly narrower than the A.O. Smith model. It measures 6.5 inches in width, while the A.O. Smith ATO-540H-N 100 is 17.8 inches wide. This difference makes the Camplux a better fit for constrained outdoor wall spaces where a slimmer profile is required for installation.
Is there a premium outdoor option with high efficiency?
The Takagi T-H3S-OS-N is labeled as the best premium pick. It delivers 8 GPM with condensing venting for high efficiency. Its compact dimensions measure 11.3 inches in length and 17.8 inches in width. This model fits outdoor spaces where emissions compliance and space saving are priorities for the user.
Which heater is best for tight outdoor spaces with single-fixture use?
The Takagi T-H3M Outdoor Natural Gas Heater is ideal for tight spots. It weighs 44 pounds and measures 13.1 inches wide. It works well for single-fixture use but may struggle with multiple simultaneous demands. Its compact size makes it suitable for installations where space is limited.
What is the flow rate of the Ranein 8.5 GPM unit?
The Ranein RHO19K-NG provides a flow rate of 5.0 GPM according to its attributes. It is designed for high-flow outdoor needs below 2,000 ft altitude. The unit weighs 44 pounds and measures 15.1 inches in width. It suits buyers who prioritize flow rate and outdoor durability in mild climates.