Looking Beyond the Eemax Commerical Tankless Water Heater? 6 Alternatives Worth a Look
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You might be evaluating the eemax commerical tankless water heater alternatives for your specific project needs. This original unit delivers 18 kW of power through a three-phase 480/277V electrical system, making it ideal for commercial spaces with the right infrastructure. Its compact 4.25"L x 12.25"W x 15.25"H frame fits tight utility areas without sacrificing output. However, most residential buyers cannot support this high-voltage three-phase requirement. You may also need a single-phase 240V option or a gas model for higher flow rates.
The 6 alternatives listed here share the 18 kW wattage benchmark but adapt to different electrical and fuel constraints. You will find single-phase electric units that fit standard home panels, as well as condensing gas models for larger households. Each selection overlaps with the original in core heating capacity while offering distinct advantages in voltage compatibility, flow rate, or physical dimensions. This guide helps you compare these specs directly. You can identify which unit matches your home’s electrical setup and hot water demands without guessing. Focus on the voltage, wattage, and size data to make a practical choice.
Our top pick: Eemax 18 kW Three-Phase Electric Tankless Water Heater.
How Alternatives Compare to Eemax
Rheem 18kW 240V Electric Tankless Water Heater
The Rheem RTEX-18 uses standard 240V power instead of the Eemax’s three-phase 480/277V system. This makes it suitable for whole-house residential use rather than commercial applications. It features precise temperature control and durable copper elements. The unit measures 14.5 inches wide and 18.5 inches long, offering a compact footprint. You should choose this if you need exact thermal settings and do not have access to three-phase electrical infrastructure. It provides efficient power modulation for residential hot water demands.
Thermomate 18kW Electric Tankless Water Heater
The Thermomate ET180 operates on 240V single-phase power, differing significantly from the Eemax’s three-phase requirement. It is designed for indoor installation and whole-house hot water with high flow needs. The unit measures 13.1 inches wide and 17.1 inches high. You must ensure your electrical panel supports the necessary dual-breaker setup for this 18 kW model. It offers strong performance for homes requiring high flow rates. Select this alternative if you have adequate residential electrical capacity but lack three-phase power.
Thermomate 18 kW 4.4 GPM Electric Tankless Water Heater
The Thermomate EH180 also uses standard electrical infrastructure rather than the Eemax’s specialized three-phase system. It provides reliable performance for homes with adequate electrical panels and limited space. The unit measures 13.2 inches wide and 17.1 inches high. It is designed for compact installations where steady hot water is needed for multiple fixtures. This model fits well where space is tight and you require consistent heating without complex commercial wiring. Choose this if you need a straightforward electric solution for residential multi-fixture use.
Rinnai 11.1 GPM Condensing Tankless Water Heater
The Rinnai RXP199iN is a gas-powered condensing unit, unlike the Eemax’s electric operation. It delivers an 11.1 GPM flow rate, significantly higher than typical electric models. The unit measures 19 inches wide and 31 inches high, making it larger than the compact Eemax. It is designed for high-flow whole-house gas needs. You should choose this if you need gas flexibility and high flow rates for large homes. Professional installation is required due to venting and gas line requirements. It offers a different fuel source for substantial hot water demands.
Ranein 18kW 4.3 GPM Electric Water Heater
The Ranein RE18K uses standard 240V power instead of the Eemax’s three-phase system. It provides a 4.3 GPM flow rate for whole-house setups. The unit measures 13.8 inches wide and 18.7 inches high. It is designed for homes with robust electrical infrastructure that demand precise temperature settings. This model offers high efficiency for multiple simultaneous uses. You should pick this if you need precise thermal control in a residential setting. It replaces the commercial three-phase requirement with standard residential electrical capabilities while maintaining strong performance.
WINTEMP 18 kW Tankless Water Heater with WiFi
The WINTEMP WN18 operates on 240V power rather than the Eemax’s three-phase 480/277V system. It includes WiFi connectivity for remote control, a feature absent in the Eemax. The unit measures 11.1 inches wide and 19.1 inches long, offering a space-saving design. It is suitable for mild climates and homes with adequate electrical capacity. You should choose this if you want convenient remote monitoring and space efficiency. It provides stable heating for residential use without the need for complex commercial electrical infrastructure.
Quick picks
Our 7 picks
Eemax 18 kW Three-Phase Electric Tankless Water Heater
Best for: commercial spaces with three-phase power
- Fuel Type
- Electric
- Wattage
- 18KW
- Voltage
- 480/277V
- Dimensions
- 4.25"L x 12.25"W x 15.25"H
- Weight
- 13.3 pounds
View on Amazon: Eemax 18 kW Three-Phase Electric Tankless Water Heater Affiliate link
This Eemax unit is a commercial-grade, three-phase electric tankless water heater. It delivers 18 kW of power at 480/277 volts. The compact metal body measures 4.25 x 12.25 x 15.25 inches and weighs 13.3 pounds. It suits commercial settings or homes with the correct high-voltage electrical infrastructure. You get efficient hot-water delivery without a storage tank.
Pros
- 18 kW heating power for fast recovery
- Three-phase 480/277V operation for commercial loads
- Compact footprint at 4.25 x 12.25 x 15.25 inches
- Lightweight 13.3 lb metal construction
Cons
- Requires 480/277V three-phase power, not standard residential 120/240V
- No listed flow rate (GPM) for capacity planning
- Lacks smart controls or remote monitoring features
Good fit if
- You have a commercial building with three-phase power
- You need high-capacity hot water for multiple fixtures
- You want a compact, wall-mounted unit
Skip if
- You only have standard 120V or 240V residential outlets
- You need a whole-house unit for a typical home
- You want smart connectivity or app control
Verdict: Eemax 18kW 480V Three-Phase Heater is a specialized solution for commercial applications requiring three-phase power. It fits businesses or workshops with the right electrical setup, not standard homes.
Rheem 18kW 240V Electric Tankless Water Heater
Best for: whole-house hot water with precise control
- 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 delivers 18 kW of heating power at 240 volts, supporting a flow rate of up to 4.4 GPM. It features an external digital thermostat with ±1°F accuracy and copper immersion elements. The unit measures 3.5 x 14.5 x 18.5 inches and weighs 14.8 pounds. This compact electric heater suits whole-house needs where precise temperature control and efficient self-modulation are priorities.
Pros
- 18 kW power output at 240V
- Up to 4.4 GPM flow rate
- External digital control with ±1°F accuracy
- Durable copper immersion heating elements
Cons
- Requires 240V electrical supply
- No smart connectivity or app control
- Fixed temperature settings without remote
Good fit if
- You need reliable whole-house hot water
- You prefer precise digital temperature control
- You have a 240V electrical circuit available
Skip if
- You require smart home integration
- You only have 120V outlets
- You need remote temperature adjustment
Verdict: Rheem RTEX-18 Electric Tankless Heater offers precise temperature control and efficient power modulation for whole-house use. It fits buyers who value exact thermal settings and durable copper elements over smart features.
Thermomate 18kW Electric Tankless Water Heater
Best for: Whole-house hot water with high flow needs
- Fuel Type
- Electric
- Flow Rate
- Up to 4.4GMP
- Wattage
- 18kW
- Installation Location
- Indoor
- Voltage
- 240V
- Temperature Control
- 80°F to 140°F, ±1°F
View on Amazon: Thermomate 18kW Electric Tankless Water Heater Affiliate link
This ThermoMate unit delivers 18kW of heating power at 240V, supporting a flow rate of up to 4.4 GPM. Its compact design measures 17.12 inches by 13.12 inches by 3.12 inches, making it suitable for indoor wall mounting. The digital display allows temperature adjustments in 1-degree increments from 80°F to 140°F. It features ETL certification and self-modulating technology to maintain efficiency. This model is designed for users needing reliable, on-demand hot water with precise control.
Pros
- High flow rate of up to 4.4 GPM for whole-house use
- Precise digital temperature control in 1-degree increments
- Compact dimensions fit tight indoor spaces
- ETL certified for safety and performance
Cons
- Requires two double-pole 40-amp breakers for installation
- Uses 8AWG wire gauge which is thicker than standard
- No outdoor weatherproofing listed for exterior use
Good fit if
- You need a high-flow unit for multiple fixtures
- You have the electrical capacity for dual 40-amp breakers
- You want precise temperature adjustments in 1-degree steps
Skip if
- You only have a single 40-amp breaker available
- You need an outdoor-rated unit for exterior walls
- You prefer a simpler single-breaker electrical setup
Verdict: ThermoMate 18kW Electric Tankless Heater provides strong performance for homes requiring high flow rates, provided you can install the necessary dual-breaker electrical system.
Thermomate 18 kW 4.4 GPM Electric Tankless Water Heater
Best for: Compact installations with strong electrical panels
- Fuel Type
- Electric
- Flow Rate
- 4.4 GPM
- Wattage
- 18kW
- Installation Location
- Indoor
- Voltage
- 240 Volt
- Temperature Control
- 80°F to 140°F
View on Amazon: Thermomate 18 kW 4.4 GPM Electric Tankless Water Heater Affiliate link
The ThermoMate EH180 is a compact, wall-mounted electric tankless water heater designed for whole-house or multi-point use. It delivers up to 4.4 GPM at 18 kW with 240 V power. The unit features a heavy-duty cast aluminum heating element and smart modulation for stable temperatures between 80°F and 140°F. It weighs only 16 lbs and measures 17.09 x 13.15 x 3.15 inches. ETL certification ensures safety for residential or light commercial applications.
Pros
- Delivers up to 4.4 GPM of hot water
- Compact dimensions of 17.09 x 13.15 x 3.15 inches
- Heavy-duty cast aluminum heating element resists scale
- ETL certified to UL-499 and CAN/CSA-C22.2 standards
Cons
- Requires two separate 40 Amp double-pole breakers
- Needs 8 AWG copper wire for installation
- Max flow rate is lower than some competitors
Good fit if
- You need a compact unit for tight spaces
- You have the electrical capacity for dual 40 Amp breakers
- You want ETL certified safety for residential use
Skip if
- You cannot install dual 40 Amp breakers
- You require more than 4.4 GPM flow rate
- You prefer a unit with digital display controls
Verdict: ThermoMate 18kW Electric Tankless Heater offers reliable performance for homes with adequate electrical infrastructure. It fits well where space is limited and steady hot water is needed for multiple fixtures.
Rinnai 11.1 GPM Condensing Tankless Water Heater
Best for: High-flow whole-house gas needs
- Fuel Type
- Natural Gas, Propane
- Flow Rate
- 11.1 GPM
- BTU
- 199k BTU
- Installation Location
- Indoor/Outdoor
- Dimensions
- 31 x 19 x 19 in
- Venting Type
- Condensing
View on Amazon: Rinnai 11.1 GPM Condensing Tankless Water Heater Affiliate link
This condensing gas tankless water heater delivers 11.1 GPM for whole-house use. It runs on propane or natural gas and fits indoors or outdoors. The unit includes a built-in pump with Smart-Circ technology to learn your usage patterns. It offers a high UEF of .98 for efficiency. You get a compact 31-inch height design. This model suits large households needing high flow rates.
Pros
- High flow rate of 11.1 GPM
- Dual fuel capability for propane or natural gas
- Indoor and outdoor installation flexibility
- Built-in pump with Smart-Circ recirculation
- Super-high energy efficiency factor of .98
Cons
- Requires WiFi Controlr module for app control
- Professional installation is recommended
- Labor warranty drops to 1 year if not registered within 90 days
Good fit if
- You need high flow for multiple fixtures
- You want indoor or outdoor versatility
- You prefer gas fuel sources
Skip if
- You want electric power only
- You prefer DIY installation
- You need app control without extra parts
Verdict: Rinnai RXP199iN 11.1 GPM Condensing Gas Heater provides strong performance for large homes. It fits buyers who need gas flexibility and high flow. You should choose this unit if you plan to hire a pro for setup.
Ranein 18kW 4.3 GPM Electric Water Heater
Best for: Precise temperature control in whole-house setups
- Fuel Type
- Electric
- Flow Rate
- 4.3 GPM
- Wattage
- 18 kW
- Voltage
- 240 V
- Temperature Control
- 86°F to 131°F, 1°F increments
- Certification
- CSA
View on Amazon: Ranein 18kW 4.3 GPM Electric Water Heater Affiliate link
The Ranein 18kW tankless water heater delivers a maximum flow rate of 4.3 GPM at 240V. It supports two to three outlets simultaneously with 99% thermal efficiency. The unit features precise temperature control from 86°F to 131°F in 1°F increments. Its compact gray design measures 18.7 x 13.8 x 3.1 inches. CSA certification ensures safety for whole-house use.
Pros
- 99% thermal efficiency for energy savings
- Precise 1°F temperature adjustment increments
- CSA certified for safety standards
- Supports 2–3 simultaneous outlets
Cons
- Requires two dedicated 40A double-pole breakers
- Needs two 8 AWG cables for installation
- Heavier at 17.4 pounds than some competitors
Good fit if
- You need precise temperature control in 1°F steps
- You have the electrical capacity for dual 40A circuits
- You want CSA certified safety for whole-house use
Skip if
- You cannot install two dedicated 40A breakers
- You require a flow rate above 4.3 GPM
- You prefer a lighter unit under 17 pounds
Verdict: Ranein 18kW Electric Tankless Heater fits homes with robust electrical infrastructure that demand precise temperature settings and high efficiency for multiple simultaneous uses.
WINTEMP 18 kW Tankless Water Heater with WiFi
Best for: WiFi remote control and space saving
- Fuel Type
- Electric
- Flow Rate
- Up to 4.3 GPM
- Wattage
- 18 kW
- Voltage
- 240V
- Certification
- ETL
- Dimensions
- 19.2 x 11.1 x 4 inches
View on Amazon: WINTEMP 18 kW Tankless Water Heater with WiFi Affiliate link
The WINTEMP WN18 is an 18kW electric tankless water heater with a 4.3 GPM flow rate at 240V. It features self-modulating technology to adjust energy use based on flow, ensuring stable temperatures. The unit includes remote WiFi control for temperature adjustments. It is ETL certified and measures 11.1 x 19.2 x 4 inches. This model suits homes in mild climates with 2–3 bathrooms needing continuous hot water.
Pros
- WiFi remote control for temperature adjustment
- 18kW power output for 4.3 GPM flow
- Self-modulating energy efficiency technology
- ETL certified for safety
Cons
- Requires 2 x 40 Amp double-pole breakers
- Needs 2 x 8/2 AWG wiring
- Limited to 2-year manufacturer warranty
Good fit if
- You want remote temperature control via WiFi
- You have a 150 Amp household service
- You need a compact wall-mounted unit
Skip if
- You cannot install 2 x 40 Amp breakers
- You need more than 4.3 GPM flow
- You prefer a longer warranty period
Verdict: WINTEMP 18kW WiFi Electric Water Heater offers convenient remote control and stable heating for mild climates. It fits homes with adequate electrical capacity seeking space-saving efficiency.
Specifications side by side
| Spec | Eemax 18 kW Three-Phase Electric Tankless Water Heater | Rheem 18kW 240V Electric Tankless Water Heater | Thermomate 18kW Electric Tankless Water Heater | Thermomate 18 kW 4.4 GPM Electric Tankless Water Heater | Rinnai 11.1 GPM Condensing Tankless Water Heater | Ranein 18kW 4.3 GPM Electric Water Heater | WINTEMP 18 kW Tankless Water Heater with WiFi |
|---|---|---|---|---|---|---|---|
| Fuel Type | Electric | Electric | Electric | Electric | Natural Gas, Propane | Electric | Electric |
| Flow Rate | not specified | 4.4 GPM | Up to 4.4GMP | 4.4 GPM | 11.1 GPM | 4.3 GPM | Up to 4.3 GPM |
| BTU | not specified | not specified | not specified | not specified | 199k BTU | not specified | not specified |
| Wattage | 18KW | 18 kW | 18kW | 18kW | not specified | 18 kW | 18 kW |
| Installation Location | not specified | not specified | Indoor | Indoor | Indoor/Outdoor | not specified | not specified |
| Voltage | 480/277V | 240 V | 240V | 240 Volt | not specified | 240 V | 240V |
| Temperature Control | not specified | ±1°F | 80°F to 140°F, ±1°F | 80°F to 140°F | not specified | 86°F to 131°F, 1°F increments | not specified |
| Certification | not specified | not specified | ETL | ETL | not specified | CSA | ETL |
| Dimensions | 4.25"L x 12.25"W x 15.25"H | 3.5 x 14.5 x 18.5 inches | 17.12" x 13.12" x 3.12" | 17.09 x 13.15 x 3.15 inches | 31 x 19 x 19 in | not specified | 19.2 x 11.1 x 4 inches |
| Use | not specified | Whole House | not specified | not specified | not specified | Whole House | Whole House |
| Venting Type | not specified | not specified | not specified | not specified | Condensing | not specified | not specified |
| Features | not specified | not specified | not specified | not specified | not specified | not specified | WiFi |
| Weight | 13.3 pounds | 14.8 pounds | not specified | not specified | 58 pounds | 17.4 pounds | 12 pounds |
| Size | 4.25"L x 12.25"W x 15.25"H | Small | 240V/18kW | not specified | 11.1 GPM | not specified | 18kW |
| Color | No Finish | Gray | Gray | Gray | Silver | Gray | Gray |
| Model | ED020480T2T | RTEX-18 | ET180 | EH180 | RXP199iN | RE18K | WN18 |
Frequently asked questions
Can I use these alternatives in a standard home instead of a commercial space?
Yes, several options are designed for residential use. The Rheem RTEX-18 and Thermomate ET180 models operate on standard 240V power, making them suitable for whole-house applications. The Eemax ED020480T2T requires a three-phase 480V system, which is rare in homes. Always verify your electrical panel capacity before installing an 18 kW unit.
Which tankless heater offers the highest flow rate for large families?
The Rinnai RXP199iN provides the highest flow rate at 11.1 GPM. It is a gas-powered condensing unit designed for large homes with high simultaneous demand. Electric alternatives like the Ranein RE18K offer 4.3 GPM, which supports multiple fixtures but delivers less total volume than the gas model. Choose based on your fuel source.
Do any of these models include WiFi connectivity for remote control?
Yes, the WINTEMP WN18 model includes WiFi features for remote control. This allows you to adjust settings from a distance. Other units like the Rheem RTEX-18 and Thermomate ET180 focus on precise temperature control and durable copper elements without smart connectivity. Select the WINTEMP if digital management is a priority for your installation.
What are the physical dimensions of the most compact electric unit?
The Eemax ED020480T2T is the most compact, measuring 4.25 inches long, 12.25 inches wide, and 15.25 inches high. It weighs 13.3 pounds. The WINTEMP WN18 is also space-saving, with a height of only 4 inches. Compare these dimensions against your available wall space to ensure proper fit during installation.
Is gas or electric better for whole-house hot water in this list?
Gas offers higher flow rates for whole-house use. The Rinnai RXP199iN delivers 11.1 GPM, ideal for large homes. Electric units like the Rheem RTEX-18 and Ranein RE18K provide 18 kW of power but have lower flow rates, typically around 4.3 GPM. Electric models are easier to install but require robust electrical infrastructure.
Which heater is best for precise temperature control?
The Rheem RTEX-18 is noted for precise temperature control and efficient power modulation. It uses durable copper elements for consistent performance. The Ranein RE18K also supports precise settings for whole-house setups. If exact thermal regulation is your main goal, these electric models provide reliable stability without relying on gas combustion variables.
Do I need a professional to install the Rinnai condensing unit?
Yes, you should hire a professional for the Rinnai RXP199iN. It is a condensing gas heater that requires specific venting and gas line connections. The electric models like the Thermomate ET180 may also need a licensed electrician for the dual-breaker setup. Professional installation ensures safety and compliance with local codes for all listed units.