As Amazon Associates, we earn from qualifying purchases. This means we may receive a small commission at no extra cost to you if you click through and make a purchase.
As an Amazon Associate we earn from qualifying purchases. Links on this page are affiliate links.
You need reliable hot water without the bulk of a tank. This list ranks the best 240V tankless water heaters by published specs. The Rheem 18kW leads because its 18 kW output and compact 3.5-inch height suit whole-home use. We compared 15 models using only listing data. Each pick matches specific household needs, from single sinks to large families. Read on to find the unit that fits your electrical capacity and space.
01 Match kilowatts to your electrical panel capacity
These units require 240V circuits with high amperage. Lower-power models like the 6kW LECLOC fit single sinks, while the 36kW WINTEMP demands robust wiring for large homes. Check your panel before buying. A 18kW unit needs 80A, and the 24kW Westinghouse requires 100A. Ensure your electrical infrastructure supports the specific wattage you choose to avoid installation issues.
| # | Product | Best for | Price |
|---|---|---|---|
| 1 | Rheem 18kW 240V Electric Tankless Water Heater Best overall | Whole-home hot water with precise temperature control | |
| 2 | Thermomate 18kW Electric Tankless Water Heater Also great | Shower and sink use with precise temp control | |
| 3 | Westinghouse 24kW WiFi Tankless Water Heater Also great | Whole-house hot water with smart control | |
| 4 | Stiebel Eltron Tempra 29 Plus 28.8kW Tankless Best premium | Whole-house hot water with high electrical capacity | |
| 5 | Orbek 14kW 240V Tankless Water Heater Also great | small households needing precise temp control | |
| 6 | WINTEMP 36kW Electric Tankless Water Heater Also great | large homes with 3-5 bathrooms | |
| 7 | WINTEMP 11kW 240V Electric Tankless Water Heater Best budget | single sink or shower applications | |
| 8 | APUS 18kW 4.4 GPM Tankless Water Heater Also great | Precise temperature control and energy efficiency | |
| 9 | Ranein 18kW 4.3 GPM Electric Water Heater Also great | whole-house hot water with multiple fixtures | |
| 10 | SIVUATEK 14kW 240V Electric Tankless Water Heater Also great | small households with one or two fixtures | |
| 11 | LECLOC 6kW 240V Hard-wired Under Sink Heater Best under sink | single sink point-of-use heating | |
| 12 | Rheem 13kW Compact Electric Tankless Water Heater Also great | Single sink or small shower applications | |
| 13 | SIVUATEK 14kW Electric Tankless Water Heater Also great | compact point-of-use shower or sink installation | |
| 14 | WINTEMP 18 kW Smart WiFi Tankless Water Heater Also great | Whole-house hot water with smart app control | |
| 15 | Mount Steel 18kW Adjustable Electric Also great | flexible power matching and scale reduction |
02 The best fit for you
- You want the best overall whole-home unit – Rheem 18kW 240V Electric Tankless Water Heater – Its 18 kW output and compact 14.5-inch width suit steady whole-home use.
- You need high flow for large homes with 3-5 bathrooms – WINTEMP 36kW Electric Tankless Water Heater – The 36 kW capacity delivers maximum flow for large households with robust electrical infrastructure.
- You want smart app control for whole-house hot water – WINTEMP 18 kW Smart WiFi Tankless Water Heater – This 18 kW unit includes smart WiFi app control for convenient whole-house management.
- You need precise temperature control for small households – Orbek 14kW 240V Tankless Water Heater – The 14 kW model offers precise digital control and a compact 9.5-inch width.
- You need compact point-of-use heating under a sink – LECLOC 6kW 240V Hard-wired Under Sink Heater – Its 6 kW output and tiny 7.1-inch footprint fit tight under-sink spaces.
Rheem 18kW 240V Electric Tankless Water Heater
Best for: Whole-home hot water with precise temperature control
- Voltage
- 240V
- Fuel Type
- Electric
- Max Flow Rate
- up to 4.4 GPM
- Heating Capacity
- 18kW
- Features
- Tankless
- Wattage
- 18 kW
This Rheem unit delivers 18kW of heating power at 240V, supporting a flow rate of up to 4.4 GPM. It features external digital thermostatic control with LED display and advanced self-modulation to adjust power based on demand. The durable copper immersion elements are field serviceable. Its compact dimensions of 18.5 by 14.5 by 3.5 inches make it suitable for whole-home installation where space is limited.
- 18kW heating capacity for strong hot water output
- Up to 4.4 GPM flow rate for multiple fixtures
- External digital control with +/- 1 degree accuracy
- Self-modulating technology adjusts power to demand
- Field serviceable copper immersion heating elements
- 18kW power is lower than the 36kW WINTEMP option
- 14.8-pound weight is heavier than smaller point-of-use models
- Fixed 18kW rating lacks the adjustable range of the Mount Steel unit
- You need a reliable whole-home heater with precise temperature control
- You want field-serviceable copper heating elements for longevity
- You prefer a compact unit with a slim 3.5-inch profile
- You require more than 18kW of heating power for very high demand
- You need an adjustable wattage setting for flexible installation
- You are looking for a lighter unit under 10 pounds
Verdict: Rheem 18kW 240V Tankless Electric Water Heater suits households needing steady hot water with precise digital control. Its self-modulating design and serviceable elements make it a solid choice for whole-home use where space is tight.
Thermomate 18kW Electric Tankless Water Heater
Best for: Shower and sink use with precise temp control
- Voltage
- 240V
- Fuel Type
- Electric
- Max Flow Rate
- Up to 4.4GMP
- Heating Capacity
- 18kW
- Installation Location
- Indoor
- Temperature Range
- 80°F to 140°F
The ThermoMate ET180 is an indoor electric tankless water heater rated at 18kW and 240V. It delivers up to 4.4 GPM with a digital display allowing 1°F adjustments between 80°F and 140°F. Self-modulating technology optimizes energy use, while separated heating elements reduce scale buildup. It requires two 40-amp double-pole breakers and 8AWG wiring. This unit suits users seeking steady flow and precise temperature control for whole-house or shower applications.
- 18kW heating capacity supports up to 4.4 GPM flow rate
- Digital display allows 1°F temperature increments from 80°F to 140°F
- Self-modulating technology adjusts energy based on inlet water temperature
- Heating elements separated from the water tube to reduce scale
- 18kW power is lower than the 24kW, 28.8kW, and 36kW options on this list
- Requires two 40-amp double-pole breakers, totaling 80A, which exceeds standard single-breaker setups
- You need a 240V unit with a digital interface for precise temperature control
- You have the electrical capacity for two 40-amp double-pole breakers
- You want a compact 17.1 x 13.1 x 3.12 inch unit for indoor installation
- You require a flow rate higher than 4.4 GPM
- You only have a single 40-amp or 50-amp breaker available
- You prefer a unit with higher wattage like 24kW or 36kW
Verdict: ThermoMate 18kW 240V Electric Tankless Heater provides stable hot water for users who prioritize precise digital temperature control and have the necessary 80A electrical infrastructure.
Westinghouse 24kW WiFi Tankless Water Heater
Best for: Whole-house hot water with smart control
- Voltage
- 240V
- Fuel Type
- Electric
- Max Flow Rate
- 5.55 GPM
- Heating Capacity
- 24 kW
- Fixture Capacity
- Shower and sink
- Installation Type
- Whole House
This Westinghouse unit delivers 24kW of heating power at 240V. It supports a maximum flow rate of 5.55 GPM, allowing you to run a shower and sink simultaneously. The device measures 17.1 inches high and 13 inches wide. It features smart WiFi control for remote temperature adjustments. You get a temperature range from 86 to 140℉. This model suits homes needing whole-house hot water with modern connectivity.
- 24kW heating capacity for strong performance
- 5.55 GPM max flow rate for multiple fixtures
- WiFi connectivity for app and voice control
- Compact 13-inch width for wall mounting
- 100A current requirement needs heavy-duty wiring
- 17.1-inch height is taller than some compact models
- You need a whole-house unit with high flow
- You want smart home integration for remote control
- You have the electrical capacity for 100A breakers
- You only need hot water for a single sink
- Your electrical panel cannot support 100A circuits
- You prefer a smaller footprint under 13 inches wide
Verdict: Westinghouse 24kW WiFi Tankless Heater fits households needing high flow and smart features. It handles simultaneous shower and sink use well if your wiring supports the 100A load.
Stiebel Eltron Tempra 29 Plus 28.8kW Tankless
Best for: Whole-house hot water with high electrical capacity
- Voltage
- 240V
- Fuel Type
- Electric
- Heating Capacity
- 28.8kW
- Features
- Tankless
- Intended Use
- Home
- Dimensions
- 4.63 × 16.6 × 14.5 inches
The Stiebel Eltron Tempra 29 Plus delivers 28.8kW of heating power at 240V. It requires three dedicated 40-amp breakers and 8-gauge copper wiring. The unit measures 16.6 inches wide and weighs 19 pounds. It offers two temperature memory presets for consistent output. This system suits homes with robust electrical service seeking high-capacity whole-house heating.
- 28.8kW heating capacity for strong flow rates
- Two temperature memory presets for easy adjustment
- Compact 4.63-inch depth saves wall space
- Made in Germany build quality
- Requires three separate 40-amp breakers
- Minimum 200-amp total service needed
- Heavier 19-pound build than smaller units
- You have a 200-amp electrical panel
- You need high flow for whole-house use
- You want preset temperature memory
- You have limited breaker space
- You cannot install 8-gauge wiring
- You need a lower power draw
Verdict: Stiebel Eltron Tempra 29 Plus 28.8kW is a high-output heater for homes with ample electrical capacity. It fits buyers who need reliable whole-house hot water and can support the required three-breaker setup.
Orbek 14kW 240V Tankless Water Heater
Best for: small households needing precise temp control
- Voltage
- 240V
- Fuel Type
- Electric
- Max Flow Rate
- 3.38 GPM
- Heating Capacity
- 14kW
- Fixture Capacity
- 2-3 points of use
- Temperature Range
- 86°F to 140°F
The Orbek 14kW tankless water heater delivers 3.38 GPM at 240V, supporting two to three fixture points. It heats water in three seconds with a 98% efficiency rating. The unit features a compact Pearl design measuring 14.2 inches high and 9.5 inches wide. An LED display allows temperature settings between 86°F and 140°F. This model suits households needing reliable, space-saving hot water for kitchen and bathroom use.
- 14kW heating capacity provides 3.38 GPM flow
- Heats water in 3 seconds for instant supply
- 98% efficiency reduces energy consumption
- LED display with 86°F to 140°F range
- Compact 14.2"H x 9.5"L x 3.1"W build
- 14kW power is lower than the 24kW, 28.8kW, and 36kW options on this list
- 3.38 GPM max flow rate is lower than the 4.3 GPM and 4.4 GPM models available
- Requires a 60-amp breaker, which is a higher electrical demand than 11kW or 12kW units
- You need a compact unit for tight spaces under a sink or in a corner
- You want precise temperature control via an LED display
- You require ETL certification for safety assurance
- You need to supply hot water to four or more fixtures simultaneously
- You prefer a higher flow rate above 4.0 GPM
- You have limited electrical capacity for a 60-amp breaker
Verdict: Orbek 14kW 240V Tankless Heater fits homes that prioritize compact dimensions and precise digital temperature control over maximum flow rates. It is a solid choice for couples or small families running two to three fixtures.
WINTEMP 36kW Electric Tankless Water Heater
Best for: large homes with 3-5 bathrooms
- Voltage
- 240V
- Fuel Type
- Electric
- Max Flow Rate
- Up to 8.7 GPM
- Heating Capacity
- 36kW
- Installation Type
- Whole House
- Features
- Tankless
The WINTEMP 36kW unit delivers up to 8.7 GPM of hot water on 240V power. Its self-modulating technology adjusts output to flow rates, ensuring stable temperatures. The compact design measures 13.7 inches wide and 21.1 inches high. It includes WiFi control for remote adjustments. This system suits large homes with three to five bathrooms in mild climates. You get continuous hot water without preheating delays.
- High 36kW heating capacity for whole-house use
- Generous 8.7 GPM maximum flow rate
- Built-in WiFi for smartphone temperature control
- Self-modulating technology optimizes energy efficiency
- ETL certified for safe operation
- Requires four 40A double-pole circuit breakers
- Draws up to 150A, demanding a 300A electrical service
- 2-year replacement warranty is shorter than typical industry standards
- You need high flow rates for multiple simultaneous showers
- You have a 300A electrical service available
- You want remote temperature control via WiFi
- You have a standard 200A electrical service
- You cannot install four separate 40A breakers
- You live in a very cold climate requiring higher delta T
Verdict: WINTEMP 36kW Electric Tankless Heater is a high-capacity solution for large households with robust electrical infrastructure. It fits buyers who need maximum flow rates and remote control features.
WINTEMP 11kW 240V Electric Tankless Water Heater
Best for: single sink or shower applications
- Voltage
- 240V
- Fuel Type
- Electric
- Max Flow Rate
- 2.6 GPM
- Heating Capacity
- 11kW
- Fixture Capacity
- 1 Shower&Sink
- Temperature Range
- 86°F–140°F
This WINTEMP unit delivers 11kW of heating power at 240V, producing up to 2.6 GPM. Its compact 9.7-inch width and 8.6-pound weight make it easy to mount in small spaces. The digital display allows temperature adjustments between 86°F and 140°F. It suits single-fixture applications like bathroom sinks or showers. The self-modulating technology adjusts power based on flow, ensuring consistent performance without wasting energy.
- 11kW heating capacity provides instant hot water
- Compact dimensions of 9.7 inches wide and 14 inches high
- Digital display adjusts temperature from 86°F to 140°F
- ETL certified for safe operation with leakage protection
- Self-modulating technology adjusts power to flow rate
- 11kW power is lower than most competitors offering 14kW to 36kW
- 2.6 GPM flow rate is lower than the 3.38 GPM and 4.4 GPM options
- 2-year warranty is shorter than standard industry expectations
- You need a compact unit for a single sink or shower
- You want a lower-power option for point-of-use applications
- You require ETL certification for safety compliance
- You need to supply hot water to multiple fixtures simultaneously
- You require a flow rate above 3.0 GPM
- You prefer a higher heating capacity for whole-house use
Verdict: WINTEMP 11kW 240V Tankless Heater fits users needing a small, efficient solution for one fixture. It is ideal for apartments or bathrooms where space and lower power consumption matter more than high flow rates.
APUS 18kW 4.4 GPM Tankless Water Heater
Best for: Precise temperature control and energy efficiency
- Voltage
- 240V
- Fuel Type
- Electric
- Max Flow Rate
- Up to 4.4 GPM
- Heating Capacity
- 18kW
- Installation Location
- Indoor
- Fixture Capacity
- 2–3 Points
This APUS unit delivers 18kW of power, supporting up to 4.4 GPM for two to three simultaneous fixtures. It features an LED display allowing precise temperature control from 86°F to 131°F in 1°F increments. The slim design measures 13.7 by 11.4 by 3.54 inches. You get 99.8% thermal efficiency through self-modulating technology that adjusts power based on flow rate.
- 18kW heating capacity supports up to 4.4 GPM flow
- LED display allows temperature settings from 86°F to 131°F
- 99.8% thermal efficiency with self-modulating power adjustment
- Slim wall-mounted design measures 13.7 by 11.4 inches
- 18kW power is lower than the 24kW, 28.8kW, and 36kW options on this list
- 15.2 pounds weight is heavier than the 6kW and 11kW competitors
- Fixture capacity for two to three points is less than the 36kW model
- You need precise digital temperature control for whole-house use
- You want high thermal efficiency with self-modulating technology
- You require a slim unit for wall mounting in tight spaces
- You need more than 4.4 GPM for heavy simultaneous use
- You prefer a lighter unit under 10 pounds for easier handling
- You require power output above 18kW for higher flow rates
Verdict: APUS 18kW 240V Electric Tankless Heater fits users who prioritize precise temperature control and energy efficiency over maximum flow capacity. It is a solid choice for homes where 4.4 GPM is sufficient for daily needs.
Ranein 18kW 4.3 GPM Electric Water Heater
Best for: whole-house hot water with multiple fixtures
- Voltage
- 240V
- Fuel Type
- Electric
- Max Flow Rate
- 4.3 GPM
- Heating Capacity
- 18 kW
- Fixture Capacity
- 2–3 household water outlets
- Temperature Range
- 86°F to 131°F
The Ranein 18kW unit delivers up to 4.3 GPM at 240V, supporting two to three household outlets simultaneously. Its 99% thermal efficiency reduces standby loss, while the 86°F to 131°F range allows precise temperature control. This compact, wall-mounted design fits whole-house needs without taking up much space.
- 18 kW heating capacity for whole-house use
- 4.3 GPM maximum flow rate
- 99% thermal efficiency rating
- Precise 1°F temperature adjustment increments
- Compact 13.8" width wall-mounted design
- Requires two dedicated 40 A double-pole breakers
- Uses two 8 AWG cables for installation
- Heavier at 17.4 pounds than some competitors
- You need a whole-house system for 2-3 outlets
- You have the electrical capacity for dual 40A circuits
- You want precise temperature control in 1°F increments
- You only need a single sink or shower
- Your electrical panel cannot support dual 40A breakers
- You prefer a lighter unit under 15 pounds
Verdict: Ranein 18kW 240V Tankless Heater suits homeowners who can install dual 40A circuits and need reliable hot water for multiple fixtures. Its high flow rate and efficiency make it a solid choice for whole-house applications.
SIVUATEK 14kW 240V Electric Tankless Water Heater
Best for: small households with one or two fixtures
- Voltage
- 240V
- Fuel Type
- Electric
- Heating Capacity
- 14 kW
- Fixture Capacity
- 1–2 points
- Temperature Range
- 86°F to 131°F
- Features
- Tankless
The SIVUATEk 14kW unit provides 240V electric heating with 99.8% thermal efficiency. It supports 1–2 simultaneous fixtures and heats water from 86°F to 131°F. The 15.1-pound Gray model features an LED display for 1°F adjustments. It requires a 60-amp circuit breaker. This compact heater suits small households needing steady flow for kitchen and bathroom use without standby loss.
- 14 kW heating power delivers instant hot water
- 99.8% thermal efficiency reduces energy waste
- LED display allows 1°F temperature increments
- Compact 15.1-pound design saves space
- ETL certified for safe operation
- 14 kW output is lower than the 24 kW and 36 kW options on this list
- Supports only 1–2 fixtures, limiting whole-house use
- Requires a 60-amp circuit breaker for installation
- You need hot water for one sink and one shower
- You want precise temperature control via an LED display
- You have the electrical capacity for a 60-amp breaker
- You need to run multiple showers at the same time
- You cannot install a 60-amp circuit breaker
- You prefer a higher wattage unit for faster recovery
Verdict: SIVUATEK 14kW 240V Tankless Water Heater fits users who prioritize energy efficiency and precise temperature control for a single bathroom or kitchen sink. It is a solid choice for small households that do not require whole-house capacity.
LECLOC 6kW 240V Hard-wired Under Sink Heater
Best for: single sink point-of-use heating
- Voltage
- 240V
- Fuel Type
- Electric
- Heating Capacity
- 6kW
- Fixture Capacity
- 1 point of use
- Installation Type
- Under Sink
- Features
- Tankless, LED Display
This LECLOC unit is a 6kW, 240V electric tankless water heater designed for under-sink installation. It serves one point of use, making it ideal for small spaces like dorms or offices. The compact 7.1-inch width fits tight areas. You get an LED display and a physical control knob for adjusting water temperature between 30°C and 55°C. It requires a 30-amp double-pole circuit breaker for safe operation.
- 6kW heating capacity provides instant hot water for a single fixture
- Compact dimensions of 7.1 x 9.8 x 2.8 inches fit under sinks
- Physical control knob allows precise temperature adjustment from 30°C to 55°C
- Includes LED digital display for clear status monitoring
- IPX4 waterproofing and overheat protection ensure safe operation
- 6kW power is significantly lower than the 11kW to 36kW options on this list
- Limited to one point of use, unlike whole-house models with higher GPM
- Requires a dedicated 30-amp double-pole circuit breaker for hard-wired installation
- You need hot water for a single sink in a small space
- You have a dedicated 240V, 30-amp electrical circuit available
- You prefer a physical knob over touchscreen controls for temperature settings
- You need to supply hot water to multiple fixtures simultaneously
- You only have a standard 120V outlet and cannot install 240V wiring
- You require a whole-house water heating solution
Verdict: LECLOC 6kW 240V Mini Tankless Heater delivers focused hot water for single sinks where space is tight. It suits users with existing 240V circuits who need a compact, safe solution for point-of-use heating.
Rheem 13kW Compact Electric Tankless Water Heater
Best for: Single sink or small shower applications
- Voltage
- 240V
- Max Flow Rate
- up to 3.17 GPM
- Heating Capacity
- 13kW
- Features
- Tankless
- Dimensions
- 12.6 × 8.25 × 3.63 inches
- Weight
- 3.97 pounds
The Rheem RTEX-13 is a compact 13kW electric tankless water heater designed for 240V circuits. It delivers up to 3.17 GPM of hot water, making it suitable for single-sink or small shower applications. The unit features a gray, compact build measuring 12.6 inches in length. It includes an external digital thermostat with 1-degree accuracy and self-modulating power control. This model is ideal for users seeking a reliable, energy-efficient solution with precise temperature management for point-of-use or light whole-house demand.
- 13kW heating capacity for efficient on-demand heating
- Compact dimensions: 12.6 x 8.25 x 3.63 inches
- External digital thermostat with 1-degree adjustment accuracy
- Self-modulating power control for energy efficiency
- Includes 1/2 NPT adapters for simple installation
- Lower 13kW power output compared to 18kW and 24kW models on the list
- Maximum flow rate of 3.17 GPM is lower than higher-capacity units
- Heavier at 3.97 pounds than some lighter competitors
- You need a compact unit for a single sink or small shower
- You want precise temperature control with 1-degree increments
- You prefer a durable copper immersion heating element design
- You require high flow rates for multiple simultaneous showers
- You need whole-house heating for large bathrooms
- You want a higher power output for faster recovery
Verdict: Rheem RTEX-13 13kW 240V Tankless Heater offers precise temperature control and a compact footprint for light-duty hot water needs. It fits well in tight spaces where high flow rates are not required.
SIVUATEK 14kW Electric Tankless Water Heater
Best for: compact point-of-use shower or sink installation
- Voltage
- 240V
- Fuel Type
- Electric
- Heating Capacity
- 14kW
- Features
- Tankless
- Application
- Shower
- Form Factor
- Compact
The SIVUATEK V7B-140B is a 14kW electric tankless water heater designed for point-of-use installation. It operates on 240V power and features a compact footprint measuring 12.2 by 12.2 by 17.3 inches. The unit weighs 16 pounds and includes a digital display with touch controls. It adjusts power based on flow rate to maintain stable temperatures. This model suits users needing efficient, on-demand hot water for specific fixtures like showers or sinks.
- 14kW heating capacity for rapid hot water delivery
- Compact dimensions of 12.2 x 12.2 x 17.3 inches
- Self-modulating technology adjusts power to flow rate
- ETL certified for safety and reliability
- Digital display with touch control panel
- 14kW power is lower than many whole-house competitors
- 16-pound weight adds bulk for wall mounting
- Fixed 1/2-inch NPT plumbing connections limit flexibility
- You need a compact heater for a single sink or shower
- You want ETL certified safety for household use
- You prefer digital controls for easy temperature adjustment
- You require whole-house hot water for multiple fixtures
- You need WiFi connectivity for remote control
- You prefer adjustable power settings between 12kW and 18kW
Verdict: The SIVUATEK 14kW 240V Electric Tankless Heater fits small households or specific fixtures where space is limited and whole-house capacity is unnecessary. It delivers reliable point-of-use heating without the bulk of larger units.
WINTEMP 18 kW Smart WiFi Tankless Water Heater
Best for: Whole-house hot water with smart app control
- Voltage
- 240V
- Fuel Type
- Electric
- Max Flow Rate
- 4.3 GPM
- Heating Capacity
- 18kW
- Temperature Range
- 86°F to 140°F
- Installation Type
- Whole House
The WINTEMP WM18V is an 18kW electric tankless water heater designed for whole-house use on a 240V circuit. It delivers up to 4.3 GPM of hot water and adjusts power via self-modulating technology. The unit includes WiFi app control and measures 15.9 x 13 x 4.2 inches. It suits households needing steady flow for two to three simultaneous fixtures.
- 18kW heating capacity supports up to 4.3 GPM flow
- WiFi app control for remote temperature and usage monitoring
- Self-modulating technology adjusts power to real-time flow
- Compact wall-mounted design saves space compared to tanks
- 18kW output is lower than the 24kW, 28.8kW, and 36kW options on this list
- Requires two 40A double-pole breakers and 8 AWG wiring, which is more demanding than lower-kW models
- Maximum temperature range of 140°F is lower than some competitors that reach 158°F
- You need whole-house hot water for two to three fixtures
- You want remote temperature control via a smartphone app
- You have the electrical capacity for two 40A breakers
- You require higher flow rates than 4.3 GPM
- You only have a single 40A breaker available
- You prefer a simpler unit without WiFi connectivity
Verdict: WINTEMP 18kW 240V Electric Water Heater provides reliable whole-house hot water with smart app control, making it a solid fit for homes that can support its electrical requirements.
Mount Steel 18kW Adjustable Electric
Best for: flexible power matching and scale reduction
- Voltage
- 240V
- Fuel Type
- Electric
- Heating Capacity
- 12kW–18kW Adjustable
- Features
- Tankless
- Application
- Point of Use
- Wattage
- 18 kW
The Mount Steel Pioneer is a 240V electric tankless water heater with adjustable power ranging from 12kW to 18kW. It measures 12.2 by 18.5 inches and uses dry-heating technology to reduce mineral buildup. This self-modulating unit maintains precise temperatures by adapting to household water needs. It suits buyers who need flexible power settings to match their home's electrical panel capacity while saving space.
- Adjustable power output from 12kW to 18kW
- Dry-heating technology reduces mineral buildup
- Compact dimensions of 12.2 by 18.5 inches
- Self-modulating for precise temperature control
- Lower maximum power of 18kW compared to higher-capacity units on the list
- Point of use application limits whole-house performance
- Fewer power configuration options than adjustable models offering 19kW to 27kW
- You need to match the heater's power draw to your electrical panel limits
- You want a compact unit for tight installation spaces
- You prefer maintenance-free operation with reduced scale buildup
- You require whole-house hot water for multiple simultaneous fixtures
- You need a maximum output higher than 18kW
- You prefer a fixed power setting over adjustable configurations
Verdict: Mount Steel 12-18kW Adjustable 240V Heater fits users who need flexible power settings to match their electrical panel capacity. It is a practical option for point-of-use installations where space is limited and scale reduction is a priority.
03 Specifications side by side
| Spec | Rheem 18kW 240V Electric Tankless Water Heater | Thermomate 18kW Electric Tankless Water Heater | Westinghouse 24kW WiFi Tankless Water Heater | Stiebel Eltron Tempra 29 Plus 28.8kW Tankless | Orbek 14kW 240V Tankless Water Heater | WINTEMP 36kW Electric Tankless Water Heater | WINTEMP 11kW 240V Electric Tankless Water Heater | APUS 18kW 4.4 GPM Tankless Water Heater | Ranein 18kW 4.3 GPM Electric Water Heater | SIVUATEK 14kW 240V Electric Tankless Water Heater | LECLOC 6kW 240V Hard-wired Under Sink Heater | Rheem 13kW Compact Electric Tankless Water Heater | SIVUATEK 14kW Electric Tankless Water Heater | WINTEMP 18 kW Smart WiFi Tankless Water Heater | Mount Steel 18kW Adjustable Electric |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Fuel Type | Electric | Electric | Electric | Electric | Electric | Electric | Electric | Electric | Electric | Electric | Electric | – | Electric | Electric | Electric |
| Max Flow Rate | up to 4.4 GPM | Up to 4.4GMP | 5.55 GPM | – | 3.38 GPM | Up to 8.7 GPM | 2.6 GPM | Up to 4.4 GPM | 4.3 GPM | – | – | up to 3.17 GPM | – | 4.3 GPM | – |
| Heating Capacity | 18kW | 18kW | 24 kW | 28.8kW | 14kW | 36kW | 11kW | 18kW | 18 kW | 14 kW | 6kW | 13kW | 14kW | 18kW | 12kW–18kW Adjustable |
| Installation Location | – | Indoor | – | – | – | – | – | Indoor | – | – | – | – | – | – | – |
| Voltage | 240V | 240 Volt | 240 V | 240 or 208-volt | 240V | 240V | 240V | 240V | 240 V | 240V | 240V | 240V | 240V | 240V | 240V |
| Fixture Capacity | – | – | Shower and sink | – | 2-3 points of use | – | 1 Shower&Sink | 2–3 Points | 2–3 household water outlets | 1–2 points | 1 point of use | – | – | – | – |
| Temperature Range | – | 80°F to 140°F | – | – | 86°F to 140°F | – | 86°F–140°F | 86–131°F | 86°F to 131°F | 86°F to 131°F | – | – | – | 86°F to 140°F | – |
| Installation Type | – | – | Whole House | – | – | Whole House | – | – | Whole House | – | Under Sink | – | – | Whole House | – |
| Features | Tankless | Tankless | Tankless | Tankless | Tankless | Tankless | Tankless | Tankless, LED Display | Tankless | Tankless | Tankless, LED Display | Tankless | Tankless | Tankless | Tankless |
| Application | – | Shower | Bathroom | – | – | – | Shower | – | – | Shower | Point of Use | – | Shower | – | Point of Use |
| Form Factor | – | – | – | – | – | – | Compact | – | – | – | – | – | Compact | – | – |
| Wattage | 18 kW | 18 kW | – | – | 14 kW | – | – | 18 kW | 18 kW | 14 kW | – | – | 14 kW | 18 kW | 18 kW |
| Intended Use | Home | – | Home | Home | – | – | – | – | – | – | – | – | – | – | – |
| Dimensions | 18.5 × 14.5 × 3.5 inches | 13.1 × 13.1 × 17.1 inches | 13 × 13 × 17.1 inches | 4.63 × 16.6 × 14.5 inches | 9.5 × 9.5 × 14.2 inches | 13.7 × 13.7 × 21.1 inches | 9.7 × 9.7 × 14 inches | 11.4 × 11.4 × 13.7 inches | 13.8 × 13.8 × 18.7 inches | 12.2 × 12.2 × 17.3 inches | 7.1 × 7.1 × 9.8 inches | 12.6 × 8.25 × 3.63 inches | 12.2 × 12.2 × 17.3 inches | 13 × 13 × 15.9 inches | 12.2 × 12.2 × 18.5 inches |
| Weight | 14.8 pounds | – | 17 pounds | 19 pounds | – | 36.1 pounds | 8.6 pounds | 15.2 pounds | 17.4 pounds | 15.1 pounds | 4 pounds | 3.97 pounds | 16 pounds | 19.5 pounds | – |
| Size | Small | 240V/18kW | L-24 | 29 (kW) | S-14 | 36kW | WN-11 | – | – | – | 6kW 240V Hard-wired | Compact | S-14 | 18 (kW) | 12-18kW Adjustable |
| Color | Gray | Gray | Gray 24 | White | Pearl | Gray | Gray | Gray | Gray | Gray | Gray | Gray | Black | Gray | Gray |
| Model | RTEX-18 | ET180 | WET-24K-G | 239223 | 14kW 2.0 Model | WN36 | YQ-WN11K | AP-ADSK180-H18 | RE18K | TSB-140 | C6000 | RTEX-13 | V7B-140B | WM18V | MST-TLS18A |
You can compare kilowatt ratings and flow capacities across the best 240V tankless water heaters before sizing your electrical panel.
04 How to choose the right one
Match kW to fixtures
Higher kilowattage delivers more simultaneous hot water. The WINTEMP 36kW suits large homes with multiple bathrooms, while the LECLOC 6kW fits a single under-sink tap. Choose based on how many fixtures run at once. Higher output requires more electrical capacity. Check your panel limits before selecting a high-kW model to avoid tripping breakers during peak use.
Check physical dimensions
Space constraints dictate which unit fits your wall. The Rheem RTEX-13 is extremely compact at 8.25 inches wide. The Stiebel Eltron Tempra 29 Plus is wider but thinner. Measure your installation spot carefully. Ensure you have clearance for wiring and access. Small footprints like the Orbek 14kW work in tight closets, while larger units need more wall space.
Verify electrical requirements
All listed models need a dedicated 240V circuit. The 36kW WINTEMP requires robust wiring, potentially three breakers. The 18kW Rheem needs an 80A circuit. Lower-power models like the 11kW WINTEMP use less amperage. Confirm your electrical panel can handle the load. Incorrect wiring causes safety hazards or tripped breakers. Always consult an electrician for high-kW installations.
Select installation type
Decide between point-of-use and whole-house systems. The LECLOC 6kW is designed for under-sink installation. Most other models, like the Rheem 18kW, serve entire homes. Point-of-use units save energy by heating water only where needed. Whole-house units provide consistent supply for showers and appliances. Choose based on whether you need one tap or full home coverage.
Consider smart features
Some units offer WiFi connectivity for remote control. The Westinghouse 24kW and WINTEMP 18kW include smart app control. These features allow you to adjust settings from your phone. Not all models have this capability. The Stiebel Eltron Tempra 29 Plus focuses on raw performance without digital extras. Decide if remote monitoring is essential for your convenience and lifestyle needs.
Evaluate temperature control
Digital displays provide precise temperature settings. The APUS 18kW includes an LED display for accurate readings. The Rheem 18kW offers self-modulating design for steady heat. Precise control prevents scalding and saves energy. Models without displays may rely on manual dials. Check if the unit includes digital feedback for better comfort and safety during daily use.
05 Frequently asked questions
Can a 240V tankless heater supply hot water to an entire house?
Yes, but you must match the kilowattage to your household size. Models like the WINTEMP 36kW are designed for large homes with three to five bathrooms. The Stiebel Eltron 28.8kW also supports whole-house use for buyers with ample electrical capacity. Lower-output units may struggle with simultaneous fixture use.
What is the smallest 240V tankless water heater available?
The LECLOC 6kW is the most compact option, measuring just 7.1 inches wide and 9.8 inches tall. It weighs only 4 pounds and is designed for point-of-use heating under a single sink. This makes it ideal for tight spaces where whole-house capacity is unnecessary.
Which 240V tankless heater includes WiFi connectivity?
The Westinghouse 24kW and the WINTEMP 18kW both offer WiFi smart control features. These units allow you to monitor and adjust settings remotely. The Westinghouse model handles high flow for whole-house use, while the WINTEMP 18kW provides reliable whole-house hot water with app integration.
How wide is the Rheem 18kW tankless water heater?
The Rheem RTEX-18 measures 14.5 inches in width. Its compact 3.5-inch height and 18.5-inch length make it easy to install in tight spaces. This footprint supports its role as a best overall choice for households needing steady hot water without taking up much wall space.
Is there an adjustable wattage 240V tankless water heater?
Yes, the Mount Steel 18kW Adjustable model allows you to change power settings. It operates between 12 kW and 18 kW to match your electrical panel capacity. This flexibility is useful for point-of-use installations where you need to reduce scale or fit specific wiring constraints.
Which heater is best for a single bathroom shower?
The WINTEMP 11kW is ideal for single shower applications. It is compact, efficient, and designed for apartments or bathrooms where space matters. The SIVUATEK 14kW is another solid choice for small households running one or two fixtures. Both prioritize precise temperature control over maximum flow rates.
Do any 240V heaters have LED displays?
The APUS 18kW and the LECLOC 6kW both feature LED displays. These screens provide precise temperature control and real-time status updates. The APUS model offers energy efficiency and 4.4 GPM flow, while the LECLOC focuses on compact under-sink heating with clear digital feedback.
