Rheem or NOVIEEX? Tankless Water Heaters Compared in 2026
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When you compare the rheem vs NOVIEEX tankless water heater options, you are choosing between two distinct heating methods. Both units provide instant hot water with precise digital temperature control. The main difference lies in their energy source and capacity. Rheem uses electricity for whole-home use, while NOVIEEX uses propane gas. This guide breaks down the specifications to help you decide which fits your home.
Key differences
| Aspect | Rheem 18kW 240V Electric Tankless Water Heater | Novieex 3.6 GPM Propane Tankless Water Heater |
|---|---|---|
| Fuel Type | Electric | Propane |
| Flow Rate | 4.4 GPM | 3.6 GPM |
| Wattage / BTU | 18 kW | 86,000 BTU |
| Voltage | 240 V | 110V-120V AC/60Hz |
| Use | Whole House | Indoor |
| Installation Location | not listed | Indoor |
Which one should you choose?
Choose Rheem 18kW 240V Electric Tankless Water Heater if
- You need a higher flow rate for multiple simultaneous fixtures.
- You prefer an electric unit that does not require gas lines.
- You want a compact device for whole-home heating.
Choose Novieex 3.6 GPM Propane Tankless Water Heater if
- You are looking for a propane gas powered unit.
- You need a lower voltage electrical connection for power.
- You want a unit with a built-in multi-protection safety system.
Verdict: The Rheem is better if you need higher flow rates for whole-home use and prefer electric power. The NOVIEEX is the right choice if you have access to propane gas and want a unit with specific indoor safety features.
Rheem vs NOVIEEX Comparison
Fuel type
The Rheem unit runs on 240V electricity, making it suitable for standard residential electrical panels without gas lines. This eliminates the need for gas venting or combustion air. The NOVIEEX model uses propane gas, requiring a connected tank or line and proper ventilation for exhaust. You must choose based on your home’s infrastructure. If you have reliable electricity but no gas access, the Rheem is the practical choice. If you already have propane and need higher heating power, the NOVIEEX fits better.
Flow rate
Rheem delivers up to 4.4 GPM, while NOVIEEX provides 3.6 GPM. The higher flow rate on the Rheem unit allows you to run more fixtures simultaneously without pressure drops. This makes it better for larger households with multiple bathrooms. The NOVIEEX unit is sufficient for point-of-use or smaller homes with lower simultaneous demand. If you need to run a shower and kitchen faucet at the same time, the Rheem offers more capacity. The difference is nearly one full gallon per minute.
Voltage
The Rheem heater requires a dedicated 240V circuit, which is standard for many electric water heaters but may require an electrician to install if your panel lacks the space. The NOVIEEX unit operates on 110V-120V AC, allowing it to plug into standard household outlets or simpler circuits. This lower voltage requirement can simplify installation for some users who cannot upgrade their electrical panel. You need to check your home’s electrical capacity before choosing the Rheem model.
Dimensions
Size matters for installation space. The Rheem unit is compact, measuring 14.5 inches wide, 18.5 inches long, and only 3.5 inches high. It weighs 14.8 pounds. The NOVIEEX unit is significantly larger, measuring 17.3 inches wide, 28.5 inches long, and 10.8 inches high, weighing 19.8 pounds. The Rheem model fits into tighter closets or utility corners. If you have limited wall space, the slim profile of the Rheem is the clear advantage for placement flexibility.
Temperature control
Both units offer precise digital temperature control with ±1°F accuracy. The Rheem features an external digital thermostatic control with an LED display. The NOVIEEX includes a built-in digital thermostat with an LED touchscreen interface. Both allow you to set specific temperatures within a wide range. The Rheem uses self-modulation to adjust power to meet demand. The NOVIEEX adjusts flame size. You get consistent water temperature with either choice, making this a tie for precision.
Installation location
The Rheem unit is designed for indoor use with simple bottom 3/4 inch NPT water connections. It does not mention outdoor or specific venting requirements. The NOVIEEX unit is explicitly rated for indoor installation only and requires professional installation with exhaust pipe included. It also notes a recommended altitude limit below 2000 feet. You must ensure your installation site meets the NOVIEEX indoor and altitude requirements. The Rheem offers more flexibility if you are unsure about ventilation constraints.
Choose the right unit for you
You have 240V power and want whole-home use
The Rheem model delivers 18 kW of electric power with a flow rate of 4.4 GPM. This capacity supports multiple fixtures in a whole-house setup. Its compact 3.5-inch depth fits tight spaces easily. You get precise digital control with ±1°F accuracy. The copper heating elements are durable and field-serviceable. This unit relies on standard electrical infrastructure rather than gas lines.
You need propane gas and high BTU output
The NOVIEEX unit runs on propane gas with 86,000 BTU of heating power. It provides up to 3.6 GPM of hot water. The wide temperature range spans from 95°F to 149°F. It includes a multi-protection system for safety against leaks and overheating. This model requires indoor installation and professional setup with 1/2-inch NPT fittings. It is ideal for homes with existing gas connections.
You prefer electric simplicity and small footprint
This electric heater weighs only 14.8 pounds and measures just 3.5 inches in height. It connects via simple bottom water fittings. The self-modulating technology adjusts power to match demand. You avoid the complexity of gas venting or exhaust pipes. The LED display shows exact temperature settings. This makes it a straightforward choice for apartments or small bathrooms where space and electrical access are key factors.
The products compared
Rheem 18kW 240V Electric Tankless Water Heater
Best for: Whole-house electric hot water needs
- Fuel Type
- Electric
- Flow Rate
- 4.4 GPM
- Wattage
- 18 kW
- Voltage
- 240 V
- Temperature Control
- ±1°F
- Dimensions
- 3.5 x 14.5 x 18.5 inches
View on Amazon: Rheem 18kW 240V Electric Tankless Water Heater Affiliate link
The Rheem RTEX-18 is an 18 kW electric tankless water heater designed for whole-house use. It delivers up to 4.4 GPM with 240V power. The unit features an external digital thermostat with ±1°F accuracy. Its compact dimensions of 3.5 x 14.5 x 18.5 inches allow for flexible installation. You get durable copper immersion heating elements that are field serviceable. This model suits households needing reliable, on-demand hot water with precise temperature control.
Pros
- 18 kW output supports up to 4.4 GPM flow rate
- External digital control with ±1°F temperature accuracy
- Field-serviceable copper immersion heating elements
- Compact 3.5-inch height for easy mounting
Cons
- Requires 240V electrical supply
- No remote control or smart connectivity listed
- Fixed 18 kW power level limits higher flow demands
Good fit if
- You need a whole-house electric solution
- You want precise temperature adjustment
- You have space for a 3.5-inch high unit
Skip if
- You only have 120V circuits available
- You require gas fuel type
- You need flow rates above 4.4 GPM
Verdict: Rheem RTEX-18 18kW Electric Tankless provides stable hot water for whole-house use with precise digital control. It fits homes with 240V power and moderate simultaneous demand.
Novieex 3.6 GPM Propane Tankless Water Heater
Best for: Indoor households needing precise temperature control
- Fuel Type
- Propane
- Flow Rate
- 3.6 GPM
- BTU
- 86,000 BTU
- Installation Location
- Indoor
- Voltage
- 110V-120V AC/60Hz
- Temperature Control
- 95°F to 149°F, ±1°F
View on Amazon: Novieex 3.6 GPM Propane Tankless Water Heater Affiliate link
The NOVIEEX RS-13 delivers up to 3.6 GPM of hot water using 86,000 BTU of propane power. It features a digital thermostat with ±1°F precision and a wide adjustable range from 95°F to 149°F. This indoor unit measures 28.5 x 17.3 x 10.8 inches and weighs 19.8 pounds. It suits households needing reliable on-demand heating with precise temperature control for multiple fixtures.
Pros
- 86,000 BTU output supports up to 3.6 GPM flow
- Digital thermostat offers ±1°F temperature precision
- Adjustable range spans 95°F to 149°F
- Compact wall-mounted design saves space
Cons
- Limited to indoor installation only
- Recommended for altitudes below 2000 feet
- Requires professional installation with 1/2 inch NPT fittings
Good fit if
- You need precise temperature control within 1 degree
- You have an indoor space for wall mounting
- You want to run a shower and sink simultaneously
Skip if
- You live above 2000 feet in altitude
- You require outdoor installation capability
- You need a flow rate higher than 3.6 GPM
Verdict: The NOVIEEX 3.6 GPM Propane Tankless Heater fits users who prioritize exact temperature stability and compact indoor placement. It provides steady hot water for moderate household use without the bulk of traditional tanks.
Specifications side by side
| Spec | Rheem 18kW 240V Electric Tankless Water Heater | Novieex 3.6 GPM Propane Tankless Water Heater |
|---|---|---|
| Fuel Type | Electric | Propane |
| Flow Rate | 4.4 GPM | 3.6 GPM |
| BTU | not stated | 86,000 BTU |
| Wattage | 18 kW | not stated |
| Installation Location | not stated | Indoor |
| Voltage | 240 V | 110V-120V AC/60Hz |
| Temperature Control | ±1°F | 95°F to 149°F, ±1°F |
| Dimensions | 3.5 x 14.5 x 18.5 inches | 28.5 x 17.3 x 10.8 in |
| Use | Whole House | not stated |
| Weight | 14.8 pounds | 19.8 pounds |
| Size | Small | 3.6GPM Propane |
| Color | Gray | Gray |
| Model | RTEX-18 | RS-13 |
Frequently asked questions
Can I install the Rheem tankless heater in my garage?
Yes, the Rheem RTEX-18 is designed for indoor installation in spaces like garages. Its small footprint, measuring just 3.5 inches in height, allows it to fit easily against a wall. The unit weighs only 14.8 pounds, making mounting straightforward. Ensure the location has proper ventilation and access to a 240V electrical panel.
Does the NOVIEEX heater require a gas line connection?
No, the NOVIEEX RS-13 runs on propane, so it does not need a permanent natural gas line. You connect it to a standard propane tank instead. This makes it suitable for homes without existing gas infrastructure. Remember that propane models require proper venting for combustion gases, so indoor installation needs careful planning.
Which unit is smaller and easier to mount?
The Rheem RTEX-18 is more compact in height, standing only 3.5 inches tall. It weighs 14.8 pounds, which is lighter than the NOVIEEX model at 19.8 pounds. While the NOVIEEX is wider and deeper, the Rheem’s slim profile makes it easier to fit in tight spaces. Both units are wall-mounted for stability.
Is the Rheem heater suitable for a whole house?
Yes, the Rheem RTEX-18 is rated for whole-house use. Its 18 kW power output supports multiple fixtures running simultaneously in moderate demand scenarios. This capacity helps maintain consistent hot water flow throughout the home. It is ideal for households with standard electrical setups that can handle the 240V requirement.
Can I use the NOVIEEX heater for outdoor showers?
No, the NOVIEEX RS-13 is specified for indoor installation only. Propane combustion requires proper ventilation and protection from the elements, which outdoor settings may not provide safely. For outdoor applications, you would need a model rated for exterior use. This unit is designed to fit inside your home for precise temperature control.
What voltage does the Rheem unit need?
The Rheem RTEX-18 requires a 240V electrical connection. You must ensure your home’s electrical panel can supply this voltage to support the 18 kW heating element. This is standard for many residential circuits but may require an upgrade if your panel is older. Check with an electrician if you are unsure about your home’s capacity.