Takagi T-H3M Outdoor Natural Gas vs Takagi Outdoor Propane Tankless Water Heater (2026): Key Differences
As an Amazon Associate we earn from qualifying purchases. Links on this page are affiliate links.
You are comparing the takagi t h3m outdoor natural gas vs outdoor propane tankless water heaters to find the right unit for your home. Both models are outdoor-condensing heaters designed for exterior installation. They share a compact footprint and high-efficiency condensing technology. The main difference lies in the fuel source. One uses natural gas while the other runs on propane. This choice dictates your gas line setup and availability.
Key differences
| Aspect | Takagi T-H3M Outdoor Natural Gas Heater | Takagi Outdoor Propane Tankless Water Heater |
|---|---|---|
| Fuel Type | Natural Gas | Propane |
| Flow Rate | not listed | 8 GPM |
| Weight | 44 pounds | 69 pounds |
| Dimensions | 17.8"L x 13.1"W x 29.5"H | 11.3"L x 17.8"W x 24.9"H |
| Venting Type | Condensing | Condensing |
Which one should you choose?
Choose Takagi T-H3M Outdoor Natural Gas Heater if
- You have an existing natural gas line available at the outdoor installation site.
- You need a lighter unit that weighs 44 pounds for easier mounting.
- You prefer a taller, narrower footprint that is 29.5 inches high.
Choose Takagi Outdoor Propane Tankless Water Heater if
- You are installing where propane is the available fuel source.
- You need a verified flow rate of 8 gallons per minute.
- You want a unit that meets Ultra-Low NOx emission standards.
Verdict: Choose the natural gas model if your property already has a natural gas connection and you prioritize a lighter weight. Select the propane model if you rely on propane tanks or need the specified 8 GPM flow rate. Both units offer condensing efficiency for outdoor use.
Takagi T-H3M vs Propane Comparison
Fuel Type
The Takagi T-H3M Outdoor Natural Gas Heater runs on natural gas, while the Takagi Outdoor Propane Tankless Water Heater uses propane. This is the primary distinction between the two units. You must choose the fuel source available at your property. Natural gas typically comes from utility lines, whereas propane requires a tank. Both models are designed for outdoor use and condensing technology, so the internal mechanics are similar. Your decision rests entirely on which fuel supply is already installed or easier to maintain at your home.
Flow Rate
The Takagi Outdoor Propane Tankless Water Heater offers an 8-gallon-per-minute flow rate, as listed in its specifications. This capacity supports multiple simultaneous uses, such as two showers and a kitchen sink. The Takagi T-H3M Outdoor Natural Gas Heater does not have a published flow rate in the provided data. Without this specific number, you cannot directly compare their hot water output capabilities. If high volume is critical for your household, the propane model provides a clear metric to evaluate against your needs.
Dimensions
Physical size varies between the two units. The Takagi T-H3M Outdoor Natural Gas Heater measures 29.5 inches in height, 13.1 inches in width, and 17.8 inches in length. The Takagi Outdoor Propane Tankless Water Heater is 24.9 inches tall, 17.8 inches wide, and 11.3 inches deep. The propane model is shorter and wider, while the natural gas unit is taller and narrower. You should check your installation space to ensure the unit fits within your designated outdoor area or enclosure without obstruction.
Weight
Weight differences affect mounting and structural support requirements. The Takagi T-H3M Outdoor Natural Gas Heater weighs 44 pounds according to its specs. The Takagi Outdoor Propane Tankless Water Heater weighs 69 pounds. The propane unit is significantly heavier, which may require a sturdier mounting bracket or wall reinforcement. You need to ensure your installation surface can support the heavier propane model. The lighter natural gas heater is easier to handle during installation.
Venting Type
Both heaters utilize condensing venting technology. This shared feature means they both achieve high energy efficiency by capturing heat from exhaust gases. Condensing units typically require specific PVC or CPVC venting materials rather than traditional metal flues. Since both models use this same efficient method, there is no difference in venting requirements based on the available data. You will need to plan for condensing venting for either choice, as this is a standard feature for both outdoor condensing units.
Which tankless heater fits your home
Natural gas users with limited space
Choose the T-H3M if your home uses natural gas. It measures 17.8 inches long and weighs 44 pounds. Its compact dimensions fit tight outdoor areas. The condensing design ensures high efficiency. You get reliable hot water without taking up much room.
Propane users needing high flow rate
Select the T-H3S if you have propane fuel. It delivers 8 gallons per minute for strong flow. The unit weighs 69 pounds and measures 17.8 inches wide. It meets ultra-low NOx emission standards. You get consistent hot water for multiple fixtures.
Buyers prioritizing lighter weight installation
The T-H3M weighs only 44 pounds. This makes it easier to handle during installation compared to heavier units. It shares the same condensing efficiency as its counterpart. You benefit from reduced structural load on your exterior wall.
The products compared
Takagi T-H3M Outdoor Natural Gas Heater
Best for: Outdoor natural gas hot water
- 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 is a condensing outdoor tankless water heater running on natural gas. It measures 29.5 inches high, 13.1 inches wide, and 17.8 inches deep. The unit weighs 44 pounds and is built in Japan. It suits you if you need a compact, weather-resistant solution for outdoor installation. The condensing design helps improve efficiency for your home's hot water needs.
Pros
- Condensing technology for higher efficiency
- Compact outdoor footprint
- Natural gas fuel type
- Lightweight at 44 pounds
Cons
- Limited to natural gas fuel
- No digital display mentioned in data
- Single fuel compatibility limits flexibility
Good fit if
- You have existing natural gas lines outdoors
- You need a space-saving outdoor unit
- You want condensing efficiency
Skip if
- You only have propane available
- You need indoor installation
- You require digital controls
Verdict: Takagi T-H3M Outdoor Natural Gas fits homeowners with outdoor natural gas access who need a compact, efficient unit. It is a solid choice for outdoor applications where space is limited.
Takagi Outdoor Propane Tankless Water Heater
Best for: outdoor propane installations 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 is the Takagi T-H3S-OS-P, a condensing outdoor tankless water heater running on propane. It delivers 8 gallons per minute for on-demand hot water. The unit measures 24.9 by 17.8 by 11.3 inches and weighs 69 pounds. It meets 2012 SCAQMD Rule 1146.2 for ultra-low NOx emissions. You should consider this model if you need a compact, high-efficiency propane solution for your outdoor space.
Pros
- 8 GPM flow rate for continuous hot water
- Condensing design for high energy efficiency
- Ultra-low NOx emissions compliant
- No pilot light reduces standby loss
Cons
- Limited to propane fuel type only
- Requires outdoor installation only
- Heavier at 69 pounds than some alternatives
Good fit if
- You have a propane supply line available
- You need an outdoor-only installation location
- You want ultra-low NOx emissions compliance
Skip if
- You require natural gas compatibility
- You need indoor installation capability
- You prefer a lighter unit under 60 pounds
Verdict: Takagi T-H3S-OS-P Propane Outdoor Heater suits outdoor propane users needing 8 GPM output. It fits homes prioritizing low emissions and compact dimensions over natural gas flexibility.
Specifications side by side
| Spec | Takagi T-H3M Outdoor Natural Gas Heater | Takagi Outdoor Propane Tankless Water Heater |
|---|---|---|
| Fuel Type | Natural Gas | Propane |
| Flow Rate | not stated | 8 GPM |
| Installation Location | Outdoor | Outdoor |
| Dimensions | 29.5 x 13.1 x 17.8 inches | 24.9 x 17.8 x 11.3 in |
| Venting Type | Condensing | Condensing |
| Capacity | not stated | 8 Gallon |
| Weight | 44 pounds | 69 pounds |
| Color | White | No Finish |
| Model | TH3MOSNG | T-H3S-OS-P |
| Size | not stated | Medium |
Frequently asked questions
Which unit is lighter for mounting?
The Takagi T-H3M Outdoor Natural Gas Heater is lighter. It weighs 44 pounds, making it easier to handle during installation. The Takagi Outdoor Propane Tankless Water Heater weighs 69 pounds. The propane model is heavier due to its internal components and construction differences.
Which heater has a smaller width?
The Takagi T-H3M Outdoor Natural Gas Heater has a narrower width. It measures 13.1 inches wide. The Takagi Outdoor Propane Tankless Water Heater is 17.8 inches wide. If your outdoor space has narrow clearance, the natural gas model fits better.
Do both models use condensing venting?
Yes, both units use condensing venting technology. This method captures heat from exhaust gases to improve efficiency. It allows for flexible venting options. You can use standard PVC piping for installation. This feature is standard on both the natural gas and propane models.
Which unit is taller?
The Takagi T-H3M Outdoor Natural Gas Heater is taller. It stands 29.5 inches high. The Takagi Outdoor Propane Tankless Water Heater is 24.9 inches high. You should check your mounting height requirements before choosing. The propane model has a more compact vertical profile.
Which model is better for tight spaces?
The Takagi T-H3M Outdoor Natural Gas Heater is more compact. It measures 17.8 inches long and 13.1 inches wide. The propane model is 11.3 inches long but 17.8 inches wide. The natural gas unit offers a smaller overall footprint for constrained outdoor areas.
Can I install either unit outdoors?
Yes, both heaters are designed for outdoor installation. They feature weather-resistant constructions suitable for exterior walls. The Takagi T-H3M and the propane model both specify outdoor use. Ensure you follow local codes for exterior gas appliance placement and clearances.
Is there a difference in depth?
Yes, the depths differ slightly. The Takagi T-H3M Outdoor Natural Gas Heater is 17.8 inches deep. The Takagi Outdoor Propane Tankless Water Heater is 11.3 inches deep. The propane model protrudes less from the wall. This may matter if you have limited clearance in front of the unit.