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 the best electric tankless water heaters that match your home’s electrical capacity and hot water demands. We compared 15 models based strictly on the specifications published on their listings. The Rheem 18kW 240V Electric Tankless Water Heater leads because its 18 kW output provides precise temperature control for small to medium households. This ranking focuses on wattage, voltage, and physical dimensions to help you decide which unit fits your space and usage needs.
01 Match Wattage to Electrical Capacity
You must verify your home’s electrical service before buying. Units range from 3.5 kW for single sinks to 36 kW for whole-house use. Higher wattage delivers more hot water but requires robust wiring and breakers. Check your panel capacity to ensure the selected unit, whether a compact 6 kW or a high-power 24 kW model, will operate safely without tripping circuits.
| # | Product | Best for | Price |
|---|---|---|---|
| 1 | Rheem 18kW 240V Electric Tankless Water Heater Best overall | small to medium households needing precise control | |
| 2 | Thermomate 18kW Electric Tankless Water Heater Also great | Single bathroom or kitchen sink hot water needs | |
| 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 strong electrical service | |
| 5 | Orbek 14kW 240V Tankless Water Heater Also great | 2-3 point use with precise temperature control | |
| 6 | WINTEMP 36kW Electric Tankless Water Heater Also great | large homes with high hot water demand | |
| 7 | WINTEMP 11kW 240V Electric Tankless Water Heater Best budget | single sink or shower point-of-use | |
| 8 | APUS 18kW 4.4 GPM Tankless Water Heater Also great | Whole-house hot water for 2-3 fixtures | |
| 9 | Ranein 18kW 4.3 GPM Electric Water Heater Also great | Precise temperature control in whole-house setups | |
| 10 | SIVUATEK 14kW 240V Electric Tankless Water Heater Also great | single sink or shower installations | |
| 11 | LECLOC 6kW 240V Hard-wired Under Sink Heater Also great | single sink hot water needs | |
| 12 | EcoSmart 8 kW Electric Tankless Water Heater Also great | Under-sink point-of-use hot water | |
| 13 | Mini Tankless 3.5kW 120V Under Sink Heater Also great | single sink low-flow applications | |
| 14 | SIVUATEK 14kW Electric Tankless Water Heater Also great | Point-of-use shower heating | |
| 15 | WINTEMP 18 kW Smart WiFi Tankless Water Heater Also great | Whole-house hot water with smart app control |
02 The best fit for you
- You need precise control for small households – Rheem 18kW 240V Electric Tankless Water Heater – The 18kW Rheem model offers durable copper elements and solid performance for precise temperature control.
- You want smart control for whole-house hot water – Westinghouse 24kW WiFi Tankless Water Heater – The Westinghouse 24kW unit includes WiFi connectivity for remote management of whole-house coverage.
- You need the most powerful unit for large homes – WINTEMP 36kW Electric Tankless Water Heater – The 36kW WINTEMP model delivers the highest output, ideal for large households with high demand.
- You require a compact heater for a single sink – EcoSmart 8 kW Electric Tankless Water Heater – The 8kW EcoSmart unit is small and lightweight, fitting well in tight under-sink spaces.
Rheem 18kW 240V Electric Tankless Water Heater
Best for: small to medium households needing precise control
- Fuel Type
- Electric
- Max Flow Rate
- up to 4.4 GPM
- Heating Capacity
- 18kW
- Voltage
- 240V
- Features
- Tankless
- Wattage
- 18 kW
This Rheem unit delivers up to 4.4 gallons per minute at 18kW. It features copper immersion heating elements and external digital thermostatic control with LED display. The self-modulation technology adjusts power to meet hot water demand. Its compact size fits under sinks or in utility areas. You get precise temperature adjustments with plus or minus 1 degree accuracy. This model suits households needing reliable on-demand hot water without a storage tank.
- 18kW heating capacity provides up to 4.4 GPM flow rate
- External digital thermostatic control with LED display
- Plus or minus 1 degree temperature accuracy
- Durable copper immersion two heating elements
- Self-modulation adjusts power to hot water demand
- 18kW power is lower than the 24kW and 36kW options on this list
- 4.4 GPM max flow rate is modest for whole-house simultaneous use
- 14.8 pounds weight adds bulk compared to smaller point-of-use units
- You need a whole-home unit with moderate flow rates
- You want precise digital temperature control with LED display
- You prefer copper heating elements for durability
- You require more than 4.4 GPM for multiple showers
- You need higher than 18kW power for large homes
- You want a unit smaller than 14.5 inches wide
Verdict: Rheem 18kW Electric Tankless Heater offers solid performance for small to medium households. It fits buyers who value precise temperature control and durable copper elements over maximum flow rate.
Thermomate 18kW Electric Tankless Water Heater
Best for: Single bathroom or kitchen sink hot water needs
- Fuel Type
- Electric
- Max Flow Rate
- Up to 4.4GMP
- Heating Capacity
- 18kW
- Installation Location
- Indoor
- Voltage
- 240 Volt
- Temperature Range
- 80°F to 140°F
The ThermoMate ET180 delivers 18kW of heating power at 240V, providing up to 4.4 GPM of hot water. It features a digital display adjustable from 80°F to 140°F and self-modulating technology for efficiency. This compact unit mounts on the wall and includes ETL certification for safety. It suits households needing reliable on-demand heating for showers or sinks without the bulk of a traditional tank.
- 18kW heating capacity supports up to 4.4 GPM flow rate
- Digital temperature display allows 1°F adjustments between 80°F and 140°F
- Self-modulating technology adjusts energy use based on input water temperature
- ETL certified with overheating and leakage protection features
- 18kW power is lower than the 24kW, 28.8kW, and 36kW options available
- Requires a substantial 80Amp breaker setup using two double-pole 40AMP breakers
- Indoor installation only, limiting placement flexibility compared to outdoor-ready models
- You need a mid-range 18kW unit for a single bathroom or kitchen sink
- You want precise temperature control with a digital display and 1°F increments
- You have the electrical capacity for two 40AMP double-pole breakers
- You require higher flow rates provided by 24kW or larger units
- You only have a single 40AMP breaker available for installation
- You need an outdoor-rated heater for exterior mounting
Verdict: ThermoMate 18kW 240V Electric Tankless Heater offers balanced performance for single-fixture use. It fits homes that prioritize precise digital temperature control and have the necessary electrical infrastructure for its 80Amp requirement.
Westinghouse 24kW WiFi Tankless Water Heater
Best for: Whole-house hot water with smart control
- Fuel Type
- Electric
- Max Flow Rate
- 5.55 GPM
- Heating Capacity
- 24 kW
- Voltage
- 240 V
- Fixture Capacity
- Shower and sink
- Installation Type
- Whole House
This Westinghouse unit delivers 24kW of heating power at 240V, supporting a maximum flow rate of 5.55 GPM. It fits whole-house needs, handling a shower and sink simultaneously. The device measures 17.1 inches high and 13 inches wide. You can control it via Wi-Fi using voice commands. The temperature range spans 86 to 140°F. It requires a 100A breaker and 8 AWG wire for installation.
- 24kW heating capacity provides high output
- 5.55 GPM max flow rate supports multiple fixtures
- Smart Wi-Fi allows remote temperature adjustments
- Compact 17.1" H x 13" W x 4.3" D design
- Requires a 100A breaker, which is higher than many competitors
- 17-pound weight is heavier than smaller under-sink units
- Maximum flow rate is lower than the 36kW WINTEMP model
- You need whole-house hot water for a shower and sink
- You want smart Wi-Fi control via voice commands
- You have the electrical capacity for a 100A breaker
- You only need hot water for a single under-sink faucet
- Your electrical panel cannot support a 100A circuit
- You require a flow rate exceeding 5.55 GPM
Verdict: Westinghouse 24kW WiFi Electric Tankless suits homes needing whole-house coverage with smart features. It fits users with adequate electrical capacity who value remote control over maximum flow speed.
Stiebel Eltron Tempra 29 Plus 28.8kW Tankless
Best for: whole-house hot water with strong electrical service
- Fuel Type
- Electric
- Heating Capacity
- 28.8kW
- Voltage
- 240 or 208-volt
- Features
- Tankless
- Intended Use
- Home
- Dimensions
- 4.63 × 16.6 × 14.5 inches
The Stiebel Eltron Tempra 29 Plus is a 28.8kW electric tankless water heater designed for whole-house use. It operates on 240V or 208V power and features two temperature memory presets for easy adjustment. You get continuous hot water without venting. The unit measures 16.6 inches wide and weighs 19 pounds. It requires three dedicated 40-amp breakers and 200-amp service, making it a robust choice for homes with adequate electrical capacity.
- High 28.8kW heating capacity for whole-house demand
- Dual voltage support for 240V or 208V systems
- Two temperature memory presets for quick adjustments
- Compact 4.63-inch depth saves wall space
- Made in Germany with a sleek white design
- Requires three separate 40-amp breakers, exceeding the single-circuit needs of many competitors
- 28.8kW power is lower than the 36kW WINTEMP option on this list
- Weighs 19 pounds, which is heavier than smaller 6kW to 14kW units
- You have a 200-amp electrical service panel
- You need a high-capacity heater for multiple simultaneous uses
- You prefer a unit with dedicated temperature presets
- You only have a 100-amp electrical service
- You want to install the unit with a single circuit breaker
- You are looking for a compact under-sink heater for one faucet
Verdict: Stiebel Eltron Tempra 29 Plus 28.8kW delivers substantial hot water flow for households with strong electrical infrastructure. It suits buyers who prioritize consistent temperature control and high output over the ease of single-breaker installation.
Orbek 14kW 240V Tankless Water Heater
Best for: 2-3 point use with precise temperature control
- Fuel Type
- Electric
- Max Flow Rate
- 3.38 GPM
- Heating Capacity
- 14kW
- Voltage
- 240V
- Fixture Capacity
- 2-3 points of use
- Temperature Range
- 86°F to 140°F
The Orbek 14kW electric tankless water heater delivers up to 3.38 GPM of hot water for 2-3 points of use. It operates on 240V power and heats water in 3 seconds. The unit features an LED display for temperature control between 86°F and 140°F. Its compact design saves space compared to traditional tanks. This model suits households needing reliable on-demand hot water with stable temperature adjustments.
- Heats water in 3 seconds for instant supply
- LED display allows precise temperature settings
- Compact size saves over 50% of space
- ETL certified for safety and protection
- Lower heating capacity at 14kW compared to 18kW, 24kW, or 36kW models on the list
- Maximum flow rate of 3.38 GPM is lower than 4.3 GPM or 4.4 GPM competitors
- Requires a 60-amp two-pole breaker, which is higher than standard 40-amp requirements for some 18kW units
- You need hot water for 2-3 points of use simultaneously
- You want an LED display for precise temperature control
- You have a 240V electrical system with a 60-amp breaker available
- You require a flow rate above 3.38 GPM for whole-house use
- You prefer a higher heating capacity like 18kW or more
- Your electrical panel cannot support a 60-amp two-pole breaker
Verdict: The Orbek 14kW Electric Tankless Heater fits buyers who prioritize precise temperature control and a compact footprint over maximum flow rate. It is a solid option for 2-3 point use when you have the necessary electrical infrastructure.
WINTEMP 36kW Electric Tankless Water Heater
Best for: large homes with high hot water demand
- Fuel Type
- Electric
- Max Flow Rate
- Up to 8.7 GPM
- Heating Capacity
- 36kW
- Voltage
- 240V
- Installation Type
- Whole House
- Features
- Tankless
The WINTEMP WN36 is a 36kW electric tankless water heater designed for whole-house use. It delivers up to 8.7 GPM at 240V, making it the most powerful option in this guide. The unit features self-modulating technology for stable temperatures and built-in WiFi for remote control. It requires four 40A breakers and weighs 36.1 pounds. This system suits homes with three to five bathrooms in mild climates.
- Highest heating capacity at 36kW
- Maximum flow rate of 8.7 GPM
- Built-in WiFi for smartphone control
- Self-modulating technology for consistent heat
- Compact wall-mounted design
- Requires four 40A circuit breakers
- Heavier build at 36.1 pounds
- Higher electrical service recommendation of 300A
- You need the highest flow rate in the guide
- You have a large home with multiple bathrooms
- You want remote temperature control via WiFi
- You have a standard 200A electrical service
- You are installing under a sink
- You cannot run four dedicated 40A breakers
Verdict: WINTEMP 36kW Electric Tankless Water Heater is the most powerful unit here, ideal for large households needing high flow. It fits homes with robust electrical infrastructure and multiple bathrooms.
WINTEMP 11kW 240V Electric Tankless Water Heater
Best for: single sink or shower point-of-use
- Fuel Type
- Electric
- Max Flow Rate
- 2.6 GPM
- Heating Capacity
- 11kW
- Voltage
- 240V
- Fixture Capacity
- 1 Shower&Sink
- Temperature Range
- 86°F–140°F
The WINTEMP 11kW unit delivers up to 2.6 GPM of instant hot water at 240V. Its compact design measures 9.7 inches wide and 14 inches high, making it suitable for under-sink or point-of-use installations. The digital display allows temperature adjustments between 86°F and 140°F. This model supports one shower and sink simultaneously, offering steady flow for small households or specific fixtures.
- 11kW heating capacity provides up to 2.6 GPM
- Digital display adjusts temperature from 86°F to 140°F
- Compact dimensions of 9.7 inches wide by 14 inches high
- ETL certified with overheat and dry-fire protection
- Lower 11kW power rating compared to 18kW or 24kW competitors
- Maximum flow of 2.6 GPM limits simultaneous multi-fixture use
- Requires 50 Amp DP breaker and 8# AWG wiring
- You need a dedicated heater for a single bathroom sink or shower
- You have the electrical capacity for a 50 Amp breaker
- You want a compact unit for under-sink installation
- You require whole-house hot water for multiple bathrooms
- You cannot install a 50 Amp double-pole breaker
- You need a flow rate higher than 2.6 GPM
Verdict: WINTEMP 11kW Electric Tankless Water Heater fits users needing reliable point-of-use hot water for a single fixture. It suits those with existing 240V electrical infrastructure who prioritize compact size over high-volume output.
APUS 18kW 4.4 GPM Tankless Water Heater
Best for: Whole-house hot water for 2-3 fixtures
- Fuel Type
- Electric
- Max Flow Rate
- Up to 4.4 GPM
- Heating Capacity
- 18kW
- Installation Location
- Indoor
- Voltage
- 240V
- Fixture Capacity
- 2–3 Points
This APUS unit delivers 18kW of power at 240V, supporting up to 4.4 GPM for two to three simultaneous fixtures. Its slim 13.7-inch height and 15.2-pound weight allow for wall mounting in tight spaces. The self-modulating technology adjusts heating to flow rate, achieving 99.8% thermal efficiency. You get precise digital control with an LED display and memory function for consistent temperature settings.
- 18kW heating capacity supports up to 4.4 GPM
- 99.8% thermal efficiency with self-modulating technology
- Slim 13.7-inch height saves vertical space
- Precise temperature control from 86°F to 131°F
- Built-in memory restores settings after power outages
- 18kW power is lower than the 24kW, 28.8kW, and 36kW models on this list
- 15.2-pound weight is heavier than the 12-pound EcoSmart ECO 8
- Requires two 40A breakers, which is more demanding than single-circuit options
- You need a whole-house heater for two to three fixtures
- You want precise digital temperature control with an LED display
- You have the electrical capacity for two 40A breakers
- You require more than 4.4 GPM flow rate
- You only have a single 40A breaker available
- You are installing under a sink with limited height clearance
Verdict: APUS 18kW Electric Tankless Water Heater fits homes needing reliable whole-house hot water for multiple fixtures. It suits buyers who value precise temperature control and have the necessary electrical infrastructure for high-power operation.
Ranein 18kW 4.3 GPM Electric Water Heater
Best for: Precise temperature control in whole-house setups
- Fuel Type
- Electric
- Max Flow Rate
- 4.3 GPM
- Heating Capacity
- 18 kW
- Voltage
- 240 V
- 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 outlets. It heats water with 99% efficiency and adjusts temperature from 86°F to 131°F in 1°F steps. The compact 13.8-inch width fits wall mounts. You get precise control via an LED display and knob. This model suits whole-house needs where space is limited but flow rate matters.
- High thermal efficiency of 99%
- Adjustable temperature in 1°F increments
- Supports 2–3 simultaneous outlets
- Max flow rate of 4.3 GPM
- Requires two 40A double-pole breakers
- Heavier at 17.4 pounds
- Lower max flow than 24kW+ competitors
- You need precise temperature control
- You have space for wall mounting
- You want high thermal efficiency
- You cannot install two 40A circuits
- You need more than 4.3 GPM
- You prefer a lighter unit
Verdict: Ranein 18kW Electric Tankless Heater offers precise temperature adjustments and high efficiency. It fits homes with adequate electrical capacity and moderate simultaneous usage.
SIVUATEK 14kW 240V Electric Tankless Water Heater
Best for: single sink or shower installations
- Fuel Type
- Electric
- Heating Capacity
- 14 kW
- Voltage
- 240V
- Fixture Capacity
- 1–2 points
- Temperature Range
- 86°F to 131°F
- Features
- Tankless
This SIVUATEK unit delivers 14 kW of heating power at 240V. It targets 1–2 fixture points with 99.8% thermal efficiency. The LED display allows precise temperature settings between 86°F and 131°F. You get instant hot water without standby loss. The compact gray design fits under sinks or on walls. It requires a 60-amp circuit breaker for safe operation.
- 14 kW heating capacity for instant hot water
- 99.8% thermal efficiency reduces energy waste
- LED display with 1°F increment adjustments
- Compact dimensions: 17.3 x 12.2 x 12.2 inches
- 14 kW power is lower than 18 kW and 24 kW competitors
- Limited to 1–2 simultaneous fixture points
- Requires a 60-amp circuit breaker for installation
- You need a compact unit for a single sink or shower
- You want precise temperature control via an LED display
- You are installing in a location with limited space
- You need to supply hot water to three or more fixtures simultaneously
- Your electrical panel cannot support a 60-amp breaker
- You require higher heating power than 14 kW
Verdict: SIVUATEK 14kW 240V Tankless Heater suits users needing efficient, space-saving hot water for one or two fixtures. It offers precise temperature control and high thermal efficiency for targeted applications.
LECLOC 6kW 240V Hard-wired Under Sink Heater
Best for: single sink hot water needs
- Fuel Type
- Electric
- Heating Capacity
- 6kW
- Voltage
- 240V
- Fixture Capacity
- 1 point of use
- Installation Type
- Under Sink
- Features
- Tankless, LED Display
The LECLOC 6kW 240V unit is a hard-wired, point-of-use heater designed for single sinks. It delivers 6kW of heating power at 240 volts, suitable for kitchen or bathroom basins. The compact 7.1 by 9.8 by 2.8 inch body weighs just 4 pounds. You get an LED display and a physical control knob for temperature settings between 30 and 55 degrees Celsius. It includes safety features like overheat and leakage protection.
- 6kW heating capacity for 240V circuits
- Compact 7.1 by 9.8 by 2.8 inch size
- Physical control knob for temperature adjustment
- LED digital display for clear readings
- 4-pound weight for easy mounting
- 6kW power is lower than the 11kW to 36kW options on this list
- Single point-of-use capacity limits whole-house application
- 7.1 inch width is narrower but designed for tight under-sink spaces
- You need hot water for a single sink only
- You have a dedicated 240V, 30-amp circuit available
- You prefer a physical knob over touchscreen controls
- You require hot water for multiple fixtures simultaneously
- You only have a standard 120V outlet available
- You need a whole-house heating solution
Verdict: LECLOC 6kW 240V Under Sink Heater provides reliable warmth for a single basin when you have the correct 240V wiring. It fits well in tight spaces where larger units cannot go.
EcoSmart 8 kW Electric Tankless Water Heater
Best for: Under-sink point-of-use hot water
- Fuel Type
- Electric
- Heating Capacity
- 8-kW
- Features
- Tankless
- Dimensions
- 4 × 8 × 12 inches
- Weight
- 4.75 pounds
The EcoSmart ECO 8 is an 8-kW electric tankless water heater designed for point-of-use applications. Its compact 12 x 8 x 4-inch footprint and 4.75-pound weight allow for easy installation in tight spaces like under sinks. This unit provides on-demand hot water without the bulk of a traditional tank, making it a practical option for smaller households or specific fixture needs.
- 8-kW heating capacity for electric power
- Compact 12 x 8 x 4-inch dimensions
- Lightweight 4.75-pound build
- Durable tankless construction
- 8-kW output is lower than the 14-36 kW units on this list
- Small physical size limits flow rate for whole-house use
- Basic feature set with no smart connectivity listed
- You need a compact heater for a single sink
- You have limited space for installation
- You want a lightweight, easy-to-mount unit
- You require high flow rates for showers
- You need whole-house hot water supply
- You want smart home integration features
Verdict: EcoSmart ECO 8 8kW Electric Heater suits buyers needing a small, lightweight unit for point-of-use hot water. It fits well in tight spaces where larger heaters cannot go.
Mini Tankless 3.5kW 120V Under Sink Heater
Best for: single sink low-flow applications
- Fuel Type
- Electric
- Heating Capacity
- 3.5kW
- Voltage
- 120V
- Fixture Capacity
- 1 Point of Use
- Installation Type
- Under Sink
- Features
- Tankless, LED Display
This 3.5kW 120V unit is designed for single-point use under sinks. It features an LED digital display and a large control knob for temperature adjustments between 30℃ and 55℃. The device includes IPX4 waterproofing and multiple safety protections. It is hard-wired and requires a 30-40 amp circuit breaker. This compact heater suits low-flow applications like kitchen or bathroom sinks.
- 3.5kW heating capacity for on-demand hot water
- LED digital display with a large control knob
- IPX4 waterproofing and overheat protection
- Compact dimensions of 7.1 x 9.8 x 7.1 inches
- 3.5kW power is lower than the 11kW to 36kW units on this list
- 120V voltage limits flow rate compared to 240V models
- Limited to one point of use, not suitable for showers
- You need hot water for a single sink
- You have a 120V electrical circuit available
- You want a compact unit under the sink
- You need to supply hot water for showers
- You require multiple fixtures to run at once
- You need higher flow rates for whole-house use
Verdict: Mini Tankless 3.5kW 120V Under Sink Heater fits users needing reliable hot water for a single sink. It offers essential safety features and easy temperature control in a small footprint.
SIVUATEK 14kW Electric Tankless Water Heater
Best for: Point-of-use shower heating
- Fuel Type
- Electric
- Heating Capacity
- 14kW
- Voltage
- 240V
- Features
- Tankless
- Application
- Shower
- Form Factor
- Compact
The SIVUATEK 14kW unit delivers instant hot water at 240V with 98% energy efficiency. Its self-modulating technology adjusts power based on flow rate to maintain stable temperatures. The compact design fits point-of-use locations, measuring 12.2 x 17.3 x 12.2 inches. It features a digital display and touch controls for easy operation. This heater is ideal for showers or washing machines where space is limited.
- 14kW heating capacity provides on-demand hot water
- Self-modulating system ensures stable temperature output
- 98% energy efficiency reduces electric charges
- Compact 16-pound build fits tight spaces
- ETL certified for safety and durability
- 14kW power is lower than the 18kW to 36kW options on this list
- 12.2 x 17.3 x 12.2 inch footprint is bulkier than mini under-sink models
- Lacks WiFi connectivity found in several competing units
- You need a compact heater for a specific point of use
- You want stable water temperature through self-modulating power
- You prefer a simple digital control interface
- You require whole-house heating for multiple simultaneous showers
- You want smart home integration via WiFi
- You are looking for the highest possible flow rate
Verdict: The SIVUATEK 14kW Electric Tankless Water Heater suits users who need reliable, efficient hot water for a single fixture without the bulk of a tank. It is a practical choice for bathroom or laundry room installations where space and stability matter.
WINTEMP 18 kW Smart WiFi Tankless Water Heater
Best for: Whole-house hot water with smart app control
- Fuel Type
- Electric
- Max Flow Rate
- 4.3 GPM
- Heating Capacity
- 18kW
- Voltage
- 240V
- Temperature Range
- 86°F to 140°F
- Installation Type
- Whole House
The WINTEMP 18kW electric tankless water heater delivers up to 4.3 GPM of hot water at 240V. It features smart WiFi control via the Tuya Smart app, allowing remote temperature adjustments between 86°F and 140°F. The unit measures 15.9 inches high and weighs 19.5 pounds. Its self-modulating technology adjusts power based on flow, ensuring efficient operation for whole-house use.
- 18kW heating capacity supports up to 4.3 GPM flow
- WiFi connectivity for remote temperature and usage monitoring
- ETL certified with multiple safety protections
- Self-modulating technology for energy efficiency
- 18kW power is lower than the 36kW WINTEMP option on this list
- Requires 75A electrical service with two 40A breakers
- Heavier at 19.5 pounds compared to lighter sink models
- You need whole-house hot water for 2–3 simultaneous uses
- You want remote temperature control via a smartphone app
- You have the required 240V electrical infrastructure installed
- You only need hot water for a single sink
- Your electrical panel cannot support a 75A load
- You prefer a unit with higher flow rates above 4.3 GPM
Verdict: WINTEMP 18kW 240V WiFi Tankless Heater provides reliable whole-house hot water with convenient app control. It suits homeowners who can accommodate its electrical requirements and want smart monitoring features.
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 | EcoSmart 8 kW Electric Tankless Water Heater | Mini Tankless 3.5kW 120V Under Sink Heater | SIVUATEK 14kW Electric Tankless Water Heater | WINTEMP 18 kW Smart WiFi Tankless Water Heater |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Fuel Type | Electric | 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 | – | – | – | – | – | 4.3 GPM |
| Heating Capacity | 18kW | 18kW | 24 kW | 28.8kW | 14kW | 36kW | 11kW | 18kW | 18 kW | 14 kW | 6kW | 8-kW | 3.5kW | 14kW | 18kW |
| Installation Location | – | Indoor | – | – | – | – | – | Indoor | – | – | – | – | – | – | – |
| Voltage | 240V | 240 Volt | 240 V | 240 or 208-volt | 240V | 240V | 240V | 240V | 240 V | 240V | 240V | – | 120V | 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 | – | 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 | – | Under Sink | – | Whole House |
| Features | Tankless | Tankless | Tankless | Tankless | Tankless | Tankless | Tankless | Tankless, LED Display | Tankless | Tankless | Tankless, LED Display | Tankless | Tankless, LED Display | Tankless | Tankless |
| Application | – | Shower | Bathroom | – | – | – | Shower | – | – | Shower | Point of Use | – | Point of Use | Shower | – |
| Form Factor | – | – | – | – | – | – | Compact | – | – | – | – | – | – | Compact | – |
| Wattage | 18 kW | 18 kW | – | – | 14 kW | – | – | 18 kW | 18 kW | 14 kW | – | – | – | 14 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 | 4 × 8 × 12 inches | 7.1 × 7.1 × 9.8 inches | 12.2 × 12.2 × 17.3 inches | 13 × 13 × 15.9 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 | 4.75 pounds | – | 16 pounds | 19.5 pounds |
| Size | Small | 240V/18kW | L-24 | 29 (kW) | S-14 | 36kW | WN-11 | – | – | – | 6kW 240V Hard-wired | 12 x 8 x 4 | 3.5kW 120V Hard-wired | S-14 | 18 (kW) |
| Color | Gray | Gray | Gray 24 | White | Pearl | Gray | Gray | Gray | Gray | Gray | Gray | White | Gray | Black | Gray |
| Model | RTEX-18 | ET180 | WET-24K-G | 239223 | 14kW 2.0 Model | WN36 | YQ-WN11K | AP-ADSK180-H18 | RE18K | TSB-140 | C6000 | ECO 8 | C3500 | V7B-140B | WM18V |
You can examine flow rates and kilowatt ratings across the best electric tankless water heaters to compare models directly.
04 Key Specs to Compare Before Buying
Check Installation Location
Your available space determines which form factor works best. Under-sink models like the LECLOC 6kW or EcoSmart 8 kW are compact enough for tight cabinets. Whole-house units such as the WINTEMP 36kW or Stiebel Eltron Tempra 29 Plus require more wall clearance. Measure your width, height, and length carefully. Ensure the unit fits without blocking access to valves. Consider the weight if mounting on drywall, as heavier units like the WINTEMP 36kW weigh 36.1 pounds. Proper placement ensures safe operation and ease of maintenance.
Match Voltage Requirements
Most listed units require 240V service, which is standard for higher-power electric heaters. However, the Mini Tankless 3.5kW model operates on 120V, making it suitable for simpler circuits. Verify your electrical panel can support the required voltage. Higher wattage units generally demand 240V to achieve sufficient flow rates. Using the wrong voltage can prevent the unit from heating water effectively. Check your breaker box specifications before installation. This step prevents electrical hazards and ensures the heater runs at its rated capacity safely.
Determine Point-of-Use Needs
If you only need hot water for a single sink, a low-wattage point-of-use unit is sufficient. The Mini Tankless 3.5kW or LECLOC 6kW models fit this category perfectly. They provide reliable warmth without overloading your electrical system. For shower applications, consider the SIVUATEK 14kW or WINTEMP 11kW units. These provide enough power for single-fixture use while maintaining precise temperature control. Avoid oversizing for single points, as it wastes energy and increases installation complexity. Match the wattage to your specific fixture count.
Evaluate Whole-House Capacity
Whole-house units must handle simultaneous usage across multiple fixtures. The WINTEMP 36kW and Stiebel Eltron Tempra 29 Plus offer high output for large homes. The Westinghouse 24kW and APUS 18kW models suit homes needing coverage for two to three fixtures. Higher kilowatt ratings generally support more concurrent taps. Check the intended use and wattage to ensure adequate flow. If your household has multiple bathrooms, prioritize higher kW units. This ensures consistent hot water delivery during peak usage times without temperature drops.
Consider Smart Features
Some units include WiFi connectivity for remote monitoring and control. The Westinghouse 24kW and WINTEMP 18kW models offer app-based management. This allows you to adjust settings or check status from your phone. Other models focus on basic operation with LED displays, like the APUS 18kW and LECLOC 6kW. Decide if remote control is essential for your lifestyle. Smart features add convenience but may require additional network setup. Basic units provide reliable performance without digital complexity. Choose based on your preference for automation versus simplicity.
05 Frequently asked questions
Which electric tankless water heater is best for a whole house?
The WINTEMP 36kW is the most powerful unit here, ideal for large households needing high flow. It fits homes with robust electrical infrastructure and multiple bathrooms. The Stiebel Eltron Tempra 29 Plus also delivers substantial hot water flow for households with strong electrical infrastructure.
Do I need WiFi for a tankless water heater?
WiFi is not required but offers remote management. The Westinghouse 24kW and WINTEMP 18kW units include connectivity for smart monitoring. You can control temperature settings remotely if you value convenience. Most other models, like the Rheem 18kW, rely on local digital controls without network features.
What is the smallest electric tankless water heater?
The EcoSmart 8 kW is a small, lightweight unit measuring 8 by 12 by 4 inches. It weighs only 4.75 pounds. The LECLOC 6kW is also very compact at 7.1 by 9.8 inches. Both fit well in tight under-sink spaces where larger heaters cannot go.
Can I use these heaters for a single shower?
Yes, several models suit single-fixture use. The Thermomate 18kW offers balanced performance for single bathroom needs. The WINTEMP 11kW is designed for point-of-use hot water for a single fixture. The SIVUATEK 14kW is also practical for bathroom installations where space and stability matter.
How much does an electric tankless water heater weigh?
Weights vary significantly by power output. The LECLOC 6kW weighs just 4 pounds, while the WINTEMP 36kW weighs 36.1 pounds. Most mid-range units, like the Rheem 18kW, weigh around 14.8 to 19.5 pounds. Heavier units generally provide higher flow rates for whole-house applications.
What voltage do electric tankless water heaters use?
Most units in this list require 240V service. The WINTEMP 36kW and Stiebel Eltron Tempra 29 Plus need robust wiring for their high wattage. A few models, like the Mini Tankless 3.5kW, operate on 120V for lower-demand single sink applications. Always verify your home’s electrical capacity before installing.
Which heater has the best temperature control?
The Rheem 18kW offers precise temperature control with durable copper elements. The Orbek 14kW also prioritizes precise adjustments for 2-3 point use. The APUS 18kW includes an LED display for clear monitoring. These models suit buyers who value consistent output over maximum flow speed.
