Rinnai or MIZUDO? Tankless Water Heaters Compared in 2026
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The comparison of rinnai vs MIZUDO tankless water heater reveals two distinct solutions for home hot water. Both brands focus on efficient heating and compact designs suitable for residential use. The main difference lies in their power source and capacity. The Rinnai model uses gas for high-flow whole-home heating, while the MIZUDO unit is an electric mini-tank designed for point-of-use tasks under sinks. You must choose based on your fuel availability and hot water needs.
Key differences
| Aspect | Rinnai 11.1 GPM Condensing Dual-Fuel Water Heater | MIZUDO 8-Gallon 120V Mini-Tank Water Heater |
|---|---|---|
| Fuel Type | Propane or Natural Gas | Electric (120V) |
| Flow Rate / Capacity | 11.1 GPM | 8.0 Gallon Tank |
| Installation Location | Indoor or Outdoor | Under Sink / Tight Spaces |
| Wattage | Not listed | 1440W |
| Venting Type | Condensing | Not listed |
Which one should you choose?
Choose Rinnai 11.1 GPM Condensing Dual-Fuel Water Heater if
- You need hot water for multiple fixtures simultaneously
- You have access to natural gas or propane lines
- You want a unit that can be installed outdoors
Choose MIZUDO 8-Gallon 120V Mini-Tank Water Heater if
- You need hot water for a single sink or appliance
- You only have a 120V electrical outlet available
- You have limited space under a cabinet or sink
Verdict: Choose the Rinnai RX199iN if you require high-volume hot water for whole-home use and have gas infrastructure. Select the MIZUDO 8-Gallon if you need a compact, electric solution for under-sink applications where space is limited.
Rinnai vs MIZUDO: Key Specs
Fuel Type
The Rinnai RX199iN operates on propane or natural gas, offering flexibility for homes with existing gas lines. This dual-fuel capability allows you to choose your preferred energy source based on local availability and cost. In contrast, the MIZUDO unit is strictly electric, requiring a 120V outlet. It draws 1440W of power to heat water. This makes the MIZUDO suitable for locations without gas infrastructure, such as remote cabins or RVs. However, it relies entirely on electrical supply. If you have access to gas, the Rinnai provides more versatility in fuel choice for your heating needs.
Flow Rate
The Rinnai delivers up to 11.1 gallons per minute (GPM). This high flow rate supports multiple fixtures running simultaneously, such as showers and kitchen sinks, making it ideal for whole-house applications. The MIZUDO is a compact 8-gallon mini-tank designed for point-of-use. It does not have a continuous flow rate listed in the same manner. Instead, it provides hot water from its stored volume for tasks like handwashing or dish rinsing. For high-demand households needing simultaneous hot water at multiple taps, the Rinnai’s continuous flow is superior. The MIZUDO serves smaller, localized needs.
Capacity
The Rinnai is a tankless unit, meaning it heats water on demand rather than storing it. It does not have a tank capacity, which saves space and prevents standby energy loss. The MIZUDO features an 8.0-gallon tank. This stored volume ensures a finite amount of hot water is available instantly before reheating is required. The Rinnai’s design allows for endless hot water, limited only by gas supply and flow settings. The MIZUDO’s 8-gallon capacity is sufficient for single sink use but will run out during extended use. Your choice depends on whether you need unlimited flow or a small reserve.
Installation Location
The Rinnai RX199iN is versatile, installable both indoors and outdoors. It features Smart Sense technology and compatible venting options, allowing placement in various environments. The MIZUDO is designed for tight spaces, specifically under sinks, in bathroom cabinets, or near washing machines. It plugs into a standard 120V outlet, simplifying installation for DIYers. The Rinnai requires professional installation and specific venting, making it less flexible for quick, temporary setups. If you need a permanent, whole-house solution, the Rinnai’s indoor/outdoor capability is a clear advantage. For temporary or under-sink use, the MIZUDO is easier to place.
Dimensions
The Rinnai measures 30.1 x 18.5 x 30.1 inches and weighs 55 pounds. It is comparable to the size of a small suitcase. The MIZUDO is more compact, measuring 17.32 x 20.8 x 15.35 inches and weighing 27 pounds. The MIZUDO’s smaller footprint allows it to fit discreetly under sinks or in tight cabinets where the Rinnai would not fit. The Rinnai’s larger size is necessary for its higher capacity and gas components. If space is a critical constraint, such as in a small RV or kitchen cabinet, the MIZUDO’s physical dimensions are more suitable. For dedicated utility areas, the Rinnai’s size is manageable.
Which tankless heater suits your home
Whole-home gas users needing high flow
You need continuous hot water for multiple fixtures. This Rinnai unit delivers 11.1 GPM, supporting up to seven simultaneous uses. Its dual-fuel capability accepts propane or natural gas. The condensing design ensures high efficiency with a UEF of .98. It fits indoor or outdoor spaces, making it a robust choice for primary household supply.
Under-sink installation in tight spaces
You require hot water for a specific sink or small area. This MIZUDO mini-tank measures 17.3 by 20.8 by 15.35 inches, fitting easily under cabinets. It plugs into a standard 120V outlet, requiring no gas lines. The 8-gallon capacity provides stored hot water for handwashing or dish rinsing in compact residential or RV settings.
Users wanting plug-and-play electric simplicity
You prefer an electric solution without complex venting. This MIZUDO heater connects via a standard plug and 1/2-inch NPT fitting. It features a 1440W heating rod for rapid temperature recovery. The adjustable thermostat ranges from 55°F to 145°F. CSA certification ensures safety with high-temp limit shut-off and overpressure protection for reliable daily use.
Gas homeowners seeking efficiency and size
You want a compact gas heater with superior efficiency. This Rinnai model measures 30.1 by 18.5 by 30.1 inches. It offers a high UEF of .98, reducing energy waste. The Smart Sense gas control allows flexible fuel selection. Professional installation is recommended to ensure proper venting and setup for optimal performance in your home.
The products compared
Rinnai 11.1 GPM Condensing Dual-Fuel Water Heater
Best for: High flow needs with flexible installation
- Fuel Type
- Natural Gas or Propane
- Flow Rate
- 11.1 GPM
- BTU
- 199k BTU
- Installation Location
- Indoor/Outdoor
- Venting Type
- Condensing
- Dimensions
- 30.1 × 18.5 × 30.1 inches
View on Amazon: Rinnai 11.1 GPM Condensing Dual-Fuel Water Heater Affiliate link
The Rinnai RX199iN delivers 11.1 GPM of hot water using natural gas or propane. Its condensing design achieves a .98 UEF for high efficiency. You can install it indoors or outdoors with the right venting. The unit measures 30.1 x 18.5 x 30.1 inches and weighs 55 pounds. This compact size fits tight spaces while supporting up to seven fixtures simultaneously.
Pros
- 11.1 GPM flow rate supports multiple fixtures
- Condensing design offers .98 energy efficiency
- Versa Vent allows indoor or outdoor installation
- Smart Sense gas control works with propane or natural gas
Cons
- WiFi control requires a separate Controlr module
- Outdoor installation needs an additional RX-OVC vent cap
- Labor warranty drops to one year if not registered within 90 days
Good fit if
- You need high flow for multiple bathrooms
- You want efficient indoor or outdoor placement
- You use natural gas or propane
Skip if
- You want built-in WiFi connectivity
- You prefer a smaller unit under 50 pounds
- You need a longer standard labor warranty
Verdict: Rinnai RX199iN 11.1 GPM Condensing Heater provides strong flow and high efficiency for homes needing hot water at seven fixtures. It suits buyers who need flexible indoor or outdoor mounting options.
MIZUDO 8-Gallon 120V Mini-Tank Water Heater
Best for: under-sink hot water for small spaces
- Fuel Type
- Electric
- Wattage
- 1440 W
- Capacity
- 8.0 gal
- Voltage
- 120 V
- Temperature Control
- 55–145°F
- Certification
- CSA
View on Amazon: MIZUDO 8-Gallon 120V Mini-Tank Water Heater Affiliate link
This MIZUDO mini tank holds 8.0 gallons of hot water at 120V. It uses a 1440W heating rod for rapid recovery at handwashing or dish rinsing. The compact 17.3 by 20.8 by 15.35 inch body fits under sinks. It plugs into a standard 15A outlet. You get adjustable thermostat control from 55°F to 145°F and CSA safety certification for reliable use in tight spaces.
Pros
- 8.0 gallon capacity for localized hot water
- 1440W heating element for fast recovery
- Compact 17.3 x 20.8 x 15.35 inch footprint
- Plugs into standard 120V 15A outlet
- CSA certified with high-temp limit shut-off
Cons
- Limited to 8.0 gallon capacity
- Requires 120V electrical connection
- No smart connectivity features listed
Good fit if
- You need hot water for a single sink
- You have limited space under a cabinet
- You want easy plug-in installation
Skip if
- You need whole-house hot water supply
- You only have 240V electrical circuits
- You require high-flow shower heating
Verdict: MIZUDO 8.0 Gal Electric Mini Tank provides reliable hot water for under-sink tasks. It fits well in small kitchens or bathrooms where space is tight and a standard outlet is available.
Specifications side by side
| Spec | Rinnai 11.1 GPM Condensing Dual-Fuel Water Heater | MIZUDO 8-Gallon 120V Mini-Tank Water Heater |
|---|---|---|
| Fuel Type | Natural Gas or Propane | Electric |
| Flow Rate | 11.1 GPM | not stated |
| BTU | 199k BTU | not stated |
| Wattage | not stated | 1440 W |
| Installation Location | Indoor/Outdoor | not stated |
| Capacity | not stated | 8.0 gal |
| Voltage | not stated | 120 V |
| Temperature Control | not stated | 55–145°F |
| Certification | not stated | CSA |
| Dimensions | not stated | 20.8 x 17.3 x 17.3 in |
| Use | not stated | Camping, RV, Under Sink |
| Venting Type | Condensing | not stated |
| Weight | 55 pounds | 27 pounds |
| Size | 11.1 GPM | not stated |
| Color | Silver | 8 Gal |
| Model | RX199iN | Etech 80 | 8.0 Gallon |
Frequently asked questions
Is Rinnai a better brand than MIZUDO?
Rinnai is generally preferred for whole-home hot water needs due to its high flow rate and dual-fuel capabilities. The Rinnai RX199iN delivers 11.1 GPM, supporting up to seven simultaneous fixtures. MIZUDO offers an 8-gallon mini-tank for under-sink use, which is better for small spaces but not for whole-house supply.
Which tankless heater has the higher flow rate?
The Rinnai model has the higher flow rate at 11.1 gallons per minute. This capacity allows it to serve multiple fixtures simultaneously. The MIZUDO unit is an 8-gallon storage tank designed for point-of-use tasks like under-sink applications, so it does not provide continuous high-flow output for the entire home.
Does MIZUDO make a tankless water heater?
The listed MIZUDO product is actually an 8-gallon electric mini-tank, not a tankless unit. It is designed for under-sink hot water in small spaces. It requires a standard electrical outlet and provides stored hot water rather than on-demand heating. For tankless options, the Rinnai model is the primary choice here.
Can the Rinnai heater be used outdoors?
Yes, the Rinnai RX199iN supports flexible indoor or outdoor mounting. Its condensing design and dual-fuel capability make it suitable for various installation environments. You can place it outside if local codes allow, which helps save indoor space while maintaining efficient hot water delivery for your home.
How big is the Rinnai water heater?
The Rinnai RX199iN measures 18.5 inches in width and 30.1 inches in both height and length. It weighs 55 pounds. These dimensions allow it to fit in standard utility spaces. Its compact footprint helps it blend into closets or mechanical rooms without taking up excessive room.
Is the MIZUDO heater easy to install?
The MIZUDO 8-gallon unit is designed for simple installation under sinks. It connects to a standard electrical outlet, so no gas lines are needed. Its compact size, measuring 17.3 inches wide and 20.8 inches high, allows it to fit into tight cabinets. This makes it a practical choice for small bathrooms or kitchens.
What fuel types does Rinnai support?
The Rinnai RX199iN operates on both propane and natural gas. This dual-fuel capability gives you flexibility based on local availability. You can choose the energy source that best suits your home setup. This adaptability ensures you can maintain efficient heating regardless of which gas line is accessible.