For most buyers seeking an electric tankless water heater 240V, I’d start with the EcoSmart ECO 11 for modest household demand, while the Stiebel Eltron Tempra 24 Trend and Rheem RTEX-24 are stronger candidates when higher output and available electrical capacity are priorities. Smaller 6–8 kW models are better suited to a sink or a limited point-of-use job than to supplying several fixtures. The key tradeoff is that more heating power can support greater hot-water demand, but it also calls for more electrical capacity and may require installation changes. Available inlet-water temperature, local climate, and simultaneous use all affect real-world flow. Read on for a comparison of all 15 options and guidance on matching one to your home.
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Key Takeaways
Output and use case separate this lineup: the 6–8 kW options are better treated as point-of-use candidates, while 18–24 kW models are aimed at higher demand, subject to local water temperature and electrical capacity.
The ECO 11 is the balanced starting point for modest demand; it sits between compact single-fixture heaters and larger units that can require more demanding electrical planning.
Two 24 kW options serve as the high-output choices: Stiebel Eltron Tempra 24 Trend and Rheem RTEX-24, but neither is a sensible upgrade unless the home can support its electrical load.
Rheem appears at several power levels—8, 11, 18, and 24 kW—making it easier to compare capacity within one product family, though the right size still depends on household demand.
Published GPM figures are not a universal promise: incoming water temperature and desired temperature rise shape actual flow, so compare each unit against local conditions rather than headline flow alone.
| EcoSmart ECO 11 Electric Tankless Water Heater, 13.8 kW at 240 V |  | Best Overall for Compact Multi-Fixture Use | Power: 13.8 kW at 240 V; 11 kW at 220 V | Current draw: 54 A | Required breaker: 60 A double-pole | VIEW ON AMAZON | See Our Full Breakdown |
| Rheem RTEX-08 8 kW Multi-Fixture Tankless Electric Water Heater, 240V |  | Best for Beginners | Power: 8 kW | Voltage: 240 V | Maximum flow rate: Up to 1.95 GPM | VIEW ON AMAZON | See Our Full Breakdown |
| Stiebel Eltron Tempra 24 Trend Electric Tankless Water Heater, 24 kW, 240 V |  | Best for Higher Household Demand | Power: 24 kW | Voltage: 240 V | Power source: Hardwired | VIEW ON AMAZON | See Our Full Breakdown |
| Ranein 13 kW Tankless Electric Water Heater, 3.1 GPM, 240V, LED Display |  | Best for Fine Temperature Adjustment | Power: 13 kW (13,000 W) | Voltage: 240 V | Circuit breaker requirement: 1 × 60 A | VIEW ON AMAZON | See Our Full Breakdown |
| CAMPLUX 6000W 240V Tankless Electric Water Heater |  | Best Point-of-Use Pick | Model: TE06ProN5 | Power: 6 kW | Voltage: 240 V | VIEW ON AMAZON | See Our Full Breakdown |
| NOVIEEX 18 kW Electric Tankless Water Heater, 240 V |  | Best for Higher Stated Flow | Power: 18 kW | Voltage: 240 V | Maximum current: 75 A | VIEW ON AMAZON | See Our Full Breakdown |
| Orbek 14 kW Electric Tankless Water Heater, 240 V, 3.38 GPM |  | Best for Mid-Range Capacity | Power: 14 kW | Voltage: 240 V | Maximum flow rate: 3.38 GPM | VIEW ON AMAZON | See Our Full Breakdown |
| ThermoMate 6 kW Electric Tankless Water Heater for Sink |  | Best for Sink-Side Installation | Power: 6 kW | Voltage: 240 V | Flow rate: Up to 1.07 GPM | VIEW ON AMAZON | See Our Full Breakdown |
| Rheem 18 kW 240 V Tankless Electric Water Heater, Gray |  | Best for Serviceable Heating Elements | Model: RTEX-18 | Power and voltage: 18 kW; 240 V | Maximum flow rate: Up to 4.4 GPM | VIEW ON AMAZON | See Our Full Breakdown |
| Ranein 18 kW Tankless Electric Water Heater, 4.3 GPM, 240 V |  | Best for Fine Temperature Adjustment | Model: RE18K | Power and voltage: 18 kW; 240 V | Maximum flow rate: 4.3 GPM | VIEW ON AMAZON | See Our Full Breakdown |
| ThermoMate 11 kW Electric Tankless Water Heater, 240 V |  | Best for Compact Point-of-Use Installation | Power and voltage: 11 kW; 240 V | Flow rate: Up to 2.15 GPM at a 35°F temperature rise | Maximum temperature: 131°F | VIEW ON AMAZON | See Our Full Breakdown |
| SIVUATEK 14 kW Electric Tankless Water Heater, 240 V |  | Best for Adjustable One- or Two-Point Use | Power and voltage: 14 kW; 240 V | Flow rate: 3.3 GPM | Temperature range: 86–131°F | VIEW ON AMAZON | See Our Full Breakdown |
| Rheem 11 kW Multi-Fixture Tankless Electric Water Heater, 240 V | | Best for Precise Setpoint Control | Power and voltage: 11 kW; 240 V single-phase | Flow rate: Up to 2.68 GPM | Temperature range: 80–140°F; digital adjustment in 1-degree increments | VIEW ON AMAZON | See Our Full Breakdown |
| CAMPLUX 6 kW Electric Tankless Water Heater, 240 V |  | Best for a Small Sink Circuit | Power and voltage: 6 kW; 240 V | Flow rate: 1.5 GPM | Temperature rise: 50°F at 1.0 GPM | VIEW ON AMAZON | See Our Full Breakdown |
| Rheem RTEX-24 24 kW 240 V Electric Tankless Water Heater |  | Best for Higher Multi-Fixture Demand | Power and voltage: 24 kW; 240 V | Flow rate: Up to 5.9 GPM | Temperature range: 80–140°F; digital adjustment in 1-degree increments | VIEW ON AMAZON | See Our Full Breakdown |
| electric tankless water heater 240v | Temperature range | Power |
|---|---|---|
| EcoSmart ECO 11 Electric Tankl | — | 13.8 kW at 240 V; 11 kW at 220 V |
| Rheem RTEX-08 8 kW Multi-Fixtu | 80–140°F | 8 kW |
| Stiebel Eltron Tempra 24 Trend | 68–140°F | 24 kW |
| Ranein 13 kW Tankless Electric | 86–131°F, adjustable in 1°F increments | 13 kW (13,000 W) |
| CAMPLUX 6000W 240V Tankless El | — | 6 kW |
| NOVIEEX 18 kW Electric Tankles | 77°F–140°F; 1°F increments | 18 kW |
| Orbek 14 kW Electric Tankless | — | 14 kW |
| ThermoMate 6 kW Electric Tankl | 85°F–131°F | 6 kW |
| Rheem 18 kW 240 V Tankless Ele | — | — |
| Ranein 18 kW Tankless Electric | 86°F–131°F; 1°F increments | — |
| ThermoMate 11 kW Electric Tank | — | — |
| SIVUATEK 14 kW Electric Tankle | 86–131°F | — |
| Rheem 11 kW Multi-Fixture Tank | 80–140°F; digital adjustment in 1-degree increments | — |
| CAMPLUX 6 kW Electric Tankless | — | — |
| Rheem RTEX-24 24 kW 240 V Elec | 80–140°F; digital adjustment in 1-degree increments | — |
More Details on Our Top Picks
EcoSmart ECO 11 Electric Tankless Water Heater, 13.8 kW at 240 V
The EcoSmart ECO 11 is my most balanced pick here for buyers who want more than sink-only service without stepping up to a larger 24 kW unit. Its self-modulating power adjusts energy use to demand, while the digital display makes outlet temperature easy to check. At 13.8 kW on 240 V, it sits between the 6–8 kW point-of-use options and the Stiebel Eltron Tempra 24 Trend, but its listed incoming-water range of 60–70°F matters: colder water can reduce the amount of hot water it can deliver. Its 60 A double-pole breaker and 6 AWG wiring also call for a suitable electrical setup. I’d choose it for modest hot-water needs, not simultaneous high-flow use across a home.
Pros:- Self-modulating operation adjusts power to heating demand.
- Compact wall-mounted body measures 12 × 9.5 × 4 inches.
- Digital display shows outlet temperature.
- Stainless steel heat exchanger and UL and CSA certifications.
Cons:- Requires a 60 A double-pole breaker and 6 AWG wiring.
- The 60–70°F incoming-water specification limits suitability in colder climates.
- Its output is below the 24 kW Stiebel Eltron Tempra 24 Trend for higher-demand homes.
Best for: Owners with warm incoming water who need a compact heater for modest multi-fixture or small-home demand and have capacity for a 60 A circuit.
Not ideal for: Households with cold incoming water, frequent simultaneous showers, or an electrical panel that cannot support the specified 60 A double-pole breaker.
- Power:13.8 kW at 240 V; 11 kW at 220 V
- Current draw:54 A
- Required breaker:60 A double-pole
- Required wire:6 AWG
- Activation flow:0.25 gallon
- Incoming water temperature:Designed for 60–70°F
- Dimensions:12 × 9.5 × 4 in.
- Certifications:UL and CSA
Our verdict“Choose the ECO 11 for compact, moderate hot-water demand with warm incoming water, but step up in capacity for colder climates or heavier simultaneous use.”
Rheem RTEX-08 8 kW Multi-Fixture Tankless Electric Water Heater, 240V
The Rheem RTEX-08 is a sensible entry point for buyers who want digital temperature adjustment and a familiar compact format, but its 8 kW output sets a clear limit. Rheem lists up to 1.95 GPM, making this a better fit for a modest fixture mix than for sustained shower demand. Compared with the 13.8 kW EcoSmart ECO 11, it draws less power but also offers less heating capacity; the 6 kW CAMPLUX is more narrowly aimed at a single sink. The adjustable 80–140°F controls are useful for setting an outlet temperature, yet the heater still needs a 40 A double-pole breaker, #8 AWG copper conductors, and a recommended 100 A household service panel. Buyers should check panel capacity before choosing it.
Pros:- Digital temperature control adjusts from 80°F to 140°F.
- Compact wall-mounted design measures 8.25 inches wide.
- Listed maximum flow rate of 1.95 GPM supports more than a sink-only use case.
- Stainless steel construction and stated pressure limit of 150 psi.
Cons:- 8 kW output limits hot-water capacity compared with the EcoSmart ECO 11 and larger units.
- Requires a 40 A double-pole breaker and #8 AWG copper conductors with ground.
- Recommended minimum 100 A household service panel may rule it out for some homes.
Best for: First-time tankless buyers with a modest hot-water load, a compatible electrical panel, and a preference for straightforward digital temperature controls.
Not ideal for: Households expecting reliable simultaneous shower use or owners whose electrical service cannot accommodate the specified circuit and panel recommendation.
- Power:8 kW
- Voltage:240 V
- Maximum flow rate:Up to 1.95 GPM
- Temperature range:80–140°F
- Electrical requirement:40 A double-pole breaker; #8 AWG copper conductors with ground
- Recommended electrical service:Minimum 100 A household service panel
- Dimensions:8.25 × 12.63 × 12.625 in.
- Warranty:5 years against leaks; 1 year parts
Our verdict“Pick the RTEX-08 for modest demand and accessible digital controls, not for a household that regularly runs multiple high-flow fixtures.”
Stiebel Eltron Tempra 24 Trend Electric Tankless Water Heater, 24 kW, 240 V
Among these five options, the Stiebel Eltron Tempra 24 Trend offers the highest stated power, making it the pick for buyers whose demand exceeds the smaller EcoSmart ECO 11 or Rheem RTEX-08. The manufacturer describes capacity as up to two showers in warm climates or roughly one to one-and-a-half in cool climates, a useful reminder that incoming water temperature changes real output. Self-modulating operation and a digital display add control without taking up much wall space, and the unit needs no venting. The tradeoff is a substantial electrical commitment: it is hardwired and calls for a recommended minimum 150 A service. Its 24 kW rating does not make it a fit for every panel or guarantee multiple showers in colder conditions.
Pros:- 24 kW output exceeds the smaller-capacity options in this batch.
- Self-modulating operation responds to hot-water demand.
- Compact wall-mounted design requires no venting.
- LED temperature display and quiet operation.
Cons:- Calls for hardwiring and a recommended minimum 150 A electrical service.
- Shower capacity falls in cooler climates, according to the stated sizing guidance.
- Larger and heavier than the 6–13.8 kW units in this batch.
Best for: Households with greater shower demand, warm-to-moderate incoming water, and electrical service able to support a 24 kW hardwired heater.
Not ideal for: Small homes with limited panel capacity, buyers seeking a simple point-of-use unit, or households expecting two showers at full flow in cold climates.
- Power:24 kW
- Voltage:240 V
- Power source:Hardwired
- Recommended minimum electrical service:150 A
- Temperature range:68–140°F
- Maximum pressure:150 psi
- Dimensions:16.63 × 14.5 × 4.63 in.
- Warranty:7 years against leakage; 3 years on parts
Our verdict“Choose the Tempra 24 Trend when household shower demand justifies its 24 kW capacity and your electrical service can support it.”
Ranein 13 kW Tankless Electric Water Heater, 3.1 GPM, 240V, LED Display
The Ranein 13 kW stands out for buyers who want precise temperature setting and built-in protective functions in a compact heater. Its controls adjust in 1°F increments, and the LED display makes the setting visible; leakage, overheat, and dry-combustion protections add safeguards. The listed maximum of 3.1 GPM is higher than the EcoSmart ECO 11’s provided specs, but maximum flow alone does not tell buyers how much water it can heat at a particular temperature rise. Like the ECO 11, this model needs a dedicated 60 A circuit, so neither is an easy fit for a constrained panel. Its 13 kW output is aimed at one or two usage points, not a substitute for the 24 kW Stiebel Eltron in a higher-demand home.
Pros:- Temperature adjusts in 1°F increments, with an 86–131°F operating range.
- LED display provides a clear temperature readout.
- Includes leakage, overheat, dry-combustion protection, and automatic shutdown.
- Compact 10.7 × 7.9 × 2.8-inch wall-mounted body.
Cons:- Requires a dedicated 60 A circuit breaker.
- The 13 kW capacity is intended for only one or two usage points.
- The stated 3.1 GPM maximum does not specify flow at a particular temperature rise.
Best for: Buyers serving one or two usage points who value fine temperature control, visible readouts, and built-in electrical and water safety protections.
Not ideal for: Large households with frequent simultaneous hot-water use or buyers who cannot provide a dedicated 60 A circuit.
- Power:13 kW (13,000 W)
- Voltage:240 V
- Circuit breaker requirement:1 × 60 A
- Maximum flow rate:3.1 GPM
- Temperature range:86–131°F, adjustable in 1°F increments
- Thermal efficiency:99%
- Dimensions:10.7 × 7.9 × 2.8 in.
- Water connection:1/2 in. NPT
Our verdict“Choose the Ranein for controlled temperature setting and modest one- or two-point demand, provided your electrical circuit can support it.”
CAMPLUX 6000W 240V Tankless Electric Water Heater
The CAMPLUX TE06ProN5 is the clearest choice in this group for a single sink or similar point of use. At 6 kW, it asks less of a home’s electrical setup than the 13 kW Ranein or 24 kW Stiebel Eltron, but that lower draw comes with lower heating capacity. The listed flow is 1.07 GPM at a 35°F temperature rise, with a 1.5 GPM maximum; those figures make it more appropriate for a nearby fixture than whole-home service. Self-modulating power, touch controls, and an LCD screen keep adjustments convenient, while the compact body can fit tight spaces. The main tradeoff is installation: it still needs a 240 V hardwired connection, and it cannot replace a larger heater for multiple simultaneous fixtures.
Pros:- 6 kW output suits a single point-of-use application.
- Self-modulating power responds to water flow and demand.
- Touch controls and LCD temperature display simplify adjustment.
- Compact body measures 10.95 × 7.4 × 2.52 inches.
Cons:- Not designed for whole-home or multi-fixture service.
- Requires a 240 V hardwired connection.
- Flow is 1.07 GPM at a 35°F rise, which limits practical use at larger temperature rises.
Best for: Owners adding hot water to one kitchen, bathroom, or utility sink who want a compact 240 V point-of-use heater.
Not ideal for: Families seeking whole-home hot water or simultaneous shower and sink service; its 6 kW output is designed for a single point of use.
- Model:TE06ProN5
- Power:6 kW
- Voltage:240 V
- Flow rate:1.07 GPM at a 35°F rise; 1.5 GPM maximum
- Maximum temperature:131°F
- Maximum pressure:150 psi
- Dimensions:10.95 × 7.4 × 2.52 in.
- Weight:4.9 lb
Our verdict“Choose the CAMPLUX for a single nearby sink and skip it if you need shower or multi-fixture capacity.”
NOVIEEX 18 kW Electric Tankless Water Heater, 240 V
The NOVIEEX stands out in this group for its stated maximum flow of 4.9 GPM, the highest among these five models. That gives it more headroom than the Rheem RTEX-18’s 4.4 GPM or the Ranein RE18K’s 4.3 GPM when several fixtures may call for hot water. Its display supports 1°F temperature adjustments, and anti-freezing, low-flow, and overheat protections add useful safeguards. The headline flow does not guarantee comfortable simultaneous use in every home: incoming water temperature, desired output temperature, and plumbing conditions all affect actual delivery. The tradeoff is a demanding installation, with two 40 A double-pole breakers and two sets of 8 AWG wiring specified, plus a one-year warranty. I’d shortlist it only after an electrician confirms the panel can support it.
Pros:- Highest stated maximum flow in this five-product group at 4.9 GPM
- Temperature can be adjusted in 1°F increments using the LED display
- Includes anti-freezing, low-water-flow, and overheat protections
- Compact wall-mounted body is 3.18 inches deep
Cons:- Requires two 40 A double-pole breakers and two sets of 8 AWG wiring
- Actual simultaneous-fixture performance depends on incoming water temperature and installation conditions
- One-year warranty is limited
Best for: Households seeking a higher-flow 18 kW unit for multiple nearby fixtures and able to support its specified electrical installation.
Not ideal for: Homes with limited panel capacity, buyers seeking a simple DIY installation, or households relying on the stated 4.9 GPM for simultaneous use without checking incoming-water conditions.
- Power:18 kW
- Voltage:240 V
- Maximum current:75 A
- Maximum flow rate:4.9 GPM
- Temperature range:77°F–140°F; 1°F increments
- Electrical requirements:Two 40 A double-pole breakers; two sets of 8 AWG wires with ground
- Water connections:3/4 in. NPT
- Dimensions and mount:11.14 × 15.86 × 3.18 in.; wall-mounted
- Warranty:1 year
Our verdict“Choose the NOVIEEX if its higher stated flow suits your fixture needs and an electrician confirms your panel can handle its substantial electrical requirements.”
Orbek 14 kW Electric Tankless Water Heater, 240 V, 3.38 GPM
The Orbek sits between the sink-focused ThermoMate 6 kW and the larger 18 kW units: its 14 kW output and 3.38 GPM maximum flow target a modest multi-fixture setup without claiming the higher capacity listed for the NOVIEEX. An LED display, temperature stability specified within 1°F, and protections against leakage, overheating, and dry heating make it a more feature-rich choice than a bare-bones point-of-use heater. The compact body can help where wall space is tight, but its electrical needs still deserve a panel check: it calls for a 60 A two-pole breaker, 6 AWG wire, and at least 150 A total household panel capacity. That is not a plug-in convenience upgrade. I’d choose it for measured, moderate demand and skip it if multiple high-flow fixtures must run together.
Pros:- 14 kW output and 3.38 GPM maximum flow offer a middle ground between sink-only and larger 18 kW models
- Temperature stability is specified within 1°F
- Includes leakage, over-temperature, and dry-heating protections
- Compact 14.2 × 9.5 × 3.1 in. body
Cons:- Requires a 60 A two-pole breaker and 6 AWG wiring
- Specified household panel capacity is at least 150 A total
- Lower stated maximum flow than the 18 kW NOVIEEX, Rheem RTEX-18, and Ranein RE18K
Best for: Owners of smaller homes or moderate-demand bathrooms who want more capacity than a sink-only heater and have a suitable electrical panel.
Not ideal for: Buyers expecting 18 kW-class flow, or households whose panel cannot support the specified 60 A circuit and 150 A total capacity.
- Power:14 kW
- Voltage:240 V
- Maximum flow rate:3.38 GPM
- Recommended points of use:2–3
- Electrical requirements:60 A two-pole breaker; 6 AWG wire; at least 150 A total household panel capacity
- Temperature range and stability:86°F–140°F; within 1°F
- Water connections:1/2 in. NPT
- Certification:ETL
- Dimensions:14.2 × 9.5 × 3.1 in.
Our verdict“Pick the Orbek for moderate multi-point demand when its electrical requirements fit your home, not for a setup that needs the higher stated flow of an 18 kW unit.”
ThermoMate 6 kW Electric Tankless Water Heater for Sink
The ThermoMate is the clear point-of-use pick in this lineup, not a smaller substitute for an 18 kW whole-home model. At 6 kW and up to 1.07 GPM, it is aimed at one sink; that modest flow can suit handwashing or similar demand close to the fixture, while falling well short of the Orbek’s 3.38 GPM for a broader multi-point role. Its compact wall-mount dimensions and self-modulating power make it a practical candidate for a location where a tank heater wastes time waiting for hot water to travel through long pipes. The 35°F rise figure also shows why the flow claim needs context: output temperature depends on incoming water temperature and flow. Installation remains hardwired on a dedicated 240 V, 30 A circuit, so compact size does not mean effortless setup.
Pros:- Compact wall-mount design fits near a sink or in a tight cabinet area
- Self-modulating power heats water on demand
- Digital display allows temperature adjustments in 1°F increments
- Specified for a 35°F temperature rise at up to 1.07 GPM
Cons:- Limited flow is not suited to larger or simultaneous household demands
- Requires a dedicated hardwired 240 V circuit with a 30 A breaker
- Maximum temperature is 131°F, below the 140°F limit listed for several larger models
Best for: Homeowners adding hot water at a remote bathroom or utility sink who can provide a dedicated 240 V circuit.
Not ideal for: Households seeking whole-home service, shower capacity, or simultaneous hot water at multiple fixtures; its 1.07 GPM flow is sink-oriented.
- Power:6 kW
- Voltage:240 V
- Flow rate:Up to 1.07 GPM
- Temperature rise:35°F
- Temperature range:85°F–131°F
- Electrical requirements:Hardwired; 30 A circuit breaker; 10 AWG minimum wire
- Water connections:1/2 in. NPT
- Maximum pressure:150 psi
- Dimensions and mount:7.5 × 11.2 × 2.52 in.; wall-mounted
Our verdict“Choose the ThermoMate for one sink close to the heater, and choose the Orbek or an 18 kW model if you need more than point-of-use flow.”
Rheem 18 kW 240 V Tankless Electric Water Heater, Gray
The Rheem RTEX-18 pairs 18 kW power with a stated 4.4 GPM maximum flow, positioning it for mid-range household demand rather than the sink-only job suited to the ThermoMate. Against the NOVIEEX, it lists less peak flow, but it has a distinctive maintenance angle: its two copper immersion heating elements are serviceable. Self-modulating power adjusts output to demand, while digital temperature control gives the owner a direct way to set the target. The compact, wall-mounted unit needs no venting, though its 14.5 × 18.25-inch dimensions still need a suitable mounting and plumbing location. A 4.4 GPM ceiling is not a promise of that flow at every temperature rise; colder incoming water can constrain simultaneous use. I’d favor it for buyers who value serviceable elements, not those choosing solely by the highest flow claim.
Pros:- Two serviceable copper immersion heating elements
- Self-modulating power adjusts to hot-water demand
- Digital temperature control with LED display
- Wall-mounted design requires no venting
Cons:- Its 4.4 GPM stated maximum is below the NOVIEEX’s 4.9 GPM
- Actual whole-home capacity depends on incoming water temperature and desired temperature rise
- At 14.5 × 18.25 inches, buyers need to plan wall and service access
Best for: Homeowners seeking an 18 kW 240 V unit with serviceable copper heating elements and digital temperature control.
Not ideal for: Buyers who need the highest stated flow in this group, or households assuming 4.4 GPM will cover several fixtures regardless of incoming-water temperature.
- Model:RTEX-18
- Power and voltage:18 kW; 240 V
- Maximum flow rate:Up to 4.4 GPM
- Maximum temperature:140°F
- Efficiency:Manufacturer states up to 99.8%
- Heating elements:Two serviceable copper immersion elements
- Maximum pressure:150
- Dimensions and weight:14.5 × 18.25 in.; 14.8 lb
- Mount and controls:Wall-mounted; LED display and external digital thermostat
Our verdict“Choose the Rheem RTEX-18 if serviceable heating elements matter more to you than the higher stated flow of the NOVIEEX.”
Ranein 18 kW Tankless Electric Water Heater, 4.3 GPM, 240 V
The Ranein RE18K is another 18 kW, 240 V option, with a stated 4.3 GPM maximum flow that sits just below the Rheem RTEX-18 and the NOVIEEX. Its differentiator is control: the LED display and knob adjust the set temperature in 1°F increments across an 86°F–131°F range, which can help owners tune output to their preferred setting. It is specified for two or three outlets, but that claim depends on fixture demand and incoming-water conditions rather than the outlet count alone. The unit is CSA certified and lists built-in safety protections, while its 3/4-inch NPT connections suit the specified plumbing size. Like the NOVIEEX, it needs two dedicated 40 A circuits with 8 AWG cable; its maximum listed temperature is 131°F, unlike models specifying 140°F.
Pros:- Temperature adjusts in 1°F increments through the LED display and control knob
- CSA certification and built-in safety protections
- 3/4 in. NPT water connections
- Wall-mounted design with a stated 4.3 GPM maximum flow
Cons:- Requires two dedicated 240 V circuits, each with a 40 A double-pole breaker and 8 AWG cable
- Stated 4.3 GPM maximum is below the NOVIEEX’s 4.9 GPM and Rheem RTEX-18’s 4.4 GPM
- Listed adjustment range tops out at 131°F, below the 140°F maximum specified for those two alternatives
Best for: Buyers who want an 18 kW unit with fine temperature adjustment, CSA certification, and plumbing connections sized at 3/4 inch NPT.
Not ideal for: Homes that cannot supply two dedicated 40 A circuits, or buyers prioritizing the highest stated flow or a listed 140°F maximum temperature.
- Model:RE18K
- Power and voltage:18 kW; 240 V
- Maximum flow rate:4.3 GPM
- Temperature range:86°F–131°F; 1°F increments
- Electrical requirements:Two dedicated 240 V circuits, each with a 40 A double-pole breaker and 8 AWG cable
- Water connection:3/4 in. NPT
- Certification:CSA
- Maximum pressure:130 psi
- Dimensions and weight:13.8 × 3.1 × 18.7 in.; 7.9 kg
Our verdict“Pick the Ranein RE18K for fine temperature control and CSA certification if its lower stated flow and substantial two-circuit electrical needs fit your home.”
ThermoMate 11 kW Electric Tankless Water Heater, 240 V
The ThermoMate makes the most sense when wall space is tight and hot water is needed at a sink or another low-flow point of use. Its 11 kW output and stated 2.15 GPM at a 35°F rise suit modest demand, while self-modulating heat adjusts to flow instead of heating a stored tank. Compared with the Rheem RTEX-11, it has a lower listed maximum temperature of 131°F and a smaller stated flow figure, so I would favor the Rheem when its wider 80–140°F control range matters. The ThermoMate’s cast aluminum heating chamber and no-water and overheating protections add practical safeguards, but it still calls for a dedicated 50 A breaker and 6 AWG wire. Its compact footprint does not make it a whole-home solution.
Pros:- Self-modulating heating adjusts output to water flow.
- Compact 9.72-by-13.78-inch wall-mounted body saves floor space.
- Cast aluminum heating chamber is designed to resist scale and corrosion.
- Includes overheating and no-water protection.
Cons:- Requires a dedicated 240 V circuit, double-pole 50 A breaker, and 6 AWG wire.
- Its 2.15 GPM rating is specified at only a 35°F temperature rise.
- Low-flow, point-of-use capacity is not suited to broad whole-home demand.
Best for: Homeowners adding on-demand hot water to one low-flow sink or a small point-of-use location with room for a dedicated 50 A circuit.
Not ideal for: Households expecting dependable hot water at several high-flow fixtures at once, or buyers who need a setpoint above 131°F.
- Power and voltage:11 kW; 240 V
- Flow rate:Up to 2.15 GPM at a 35°F temperature rise
- Maximum temperature:131°F
- Electrical requirement:46 A maximum draw; double-pole 50 A breaker; 6 AWG wire
- Water connections:1/2 in. NPT male ports; side connections
- Maximum pressure:150 psi
- Dimensions and weight:9.72 × 13.78 in.; 11 lb
- Efficiency and certification:99%; ETL certified
Our verdict“Choose the ThermoMate for a compact, protected point-of-use setup, but pick the Rheem RTEX-11 if its higher listed flow and wider temperature range better match your needs.”
SIVUATEK 14 kW Electric Tankless Water Heater, 240 V
The SIVUATEK’s clearest advantage over the 11 kW ThermoMate and Rheem RTEX-11 is its 14 kW rating and stated 3.3 GPM flow, aimed at one or two simultaneous points of use. An LED display with 1°F temperature adjustments gives buyers more direct control than a basic point-of-use unit, and leakage and overheating protection with automatic shutoff adds useful fault response. Its 86–131°F range remains narrower at the upper end than the Rheem RTEX-11’s 80–140°F controls, however, and the stated flow figure does not specify a temperature rise. The unit also needs a 60 A breaker, so its compact wall-mount format does not mean simple electrical installation. I would verify the dimensions before planning a tight under-sink fit because the supplied measurements conflict.
Pros:- 14 kW output and a stated 3.3 GPM flow rate target modest multi-point use.
- LED display offers temperature adjustment in 1°F increments.
- Leakage and overheating protection include automatic shutoff.
- Wall-mount design can suit under-sink or other compact installations.
Cons:- Requires a 60 A circuit breaker.
- The listed dimensions conflict with the dimensions in the product description.
- Its one- or two-point-use scope and 131°F ceiling limit its fit for larger demand.
Best for: Buyers who want adjustable digital temperature control for one or two nearby fixtures and already have capacity for a 60 A circuit.
Not ideal for: Shoppers planning a precise tight-space installation without confirming dimensions, or households needing multiple high-demand fixtures supplied together.
- Power and voltage:14 kW; 240 V
- Flow rate:3.3 GPM
- Temperature range:86–131°F
- Thermal efficiency:99.8%
- Electrical requirement:One 60 A circuit breaker
- Water connection:1/2 in. NPT
- Dimensions:Description: 15.87 × 11.14 × 2.87 in.; listed item dimensions: 12.2 × 17.25 in.
- Weight and certification:6.85 kg; ETL
Our verdict“Pick the SIVUATEK for digitally controlled one- or two-point service if you can confirm its dimensions and support the 60 A circuit.”
Rheem 11 kW Multi-Fixture Tankless Electric Water Heater, 240 V
The Rheem RTEX-11 earns its place for buyers who value fine temperature control in a compact point-of-use heater. Its digital controls adjust in 1-degree increments across an 80–140°F range, giving it more setpoint flexibility than the ThermoMate 11 kW, which tops out at 131°F. The Rheem is also listed at up to 2.68 GPM, though actual delivery depends on incoming water temperature and the needed rise. Like the ThermoMate, it needs a 50 A double-pole breaker; the specified #8 AWG copper conductors and recommended 100 A household service make electrical planning part of the purchase. It requires no venting and occupies little wall space, but its output remains aimed at point-of-use demand rather than unrestricted whole-home use.
Pros:- Digital temperature setting adjusts in 1-degree increments.
- 80–140°F control range is broader than the ThermoMate 11 kW’s listed range.
- Up to 2.68 GPM listed flow in a compact wall-mounted unit.
- No venting is required; includes a five-year leak and one-year parts warranty.
Cons:- Requires a 50 A double-pole breaker and #8 AWG copper conductors with ground.
- Recommended household service is at least 100 A.
- Point-of-use output is limited for simultaneous high-demand fixtures.
Best for: Homeowners who need a compact point-of-use heater with finely adjustable setpoints and a listed range reaching 140°F.
Not ideal for: Buyers who cannot support a 50 A circuit or who expect one small 11 kW heater to serve several high-flow fixtures simultaneously.
- Power and voltage:11 kW; 240 V single-phase
- Flow rate:Up to 2.68 GPM
- Temperature range:80–140°F; digital adjustment in 1-degree increments
- Efficiency:99.8%
- Electrical requirement:One 50 A double-pole breaker; #8 AWG copper conductors with ground
- Recommended household service:Minimum 100 A
- Dimensions and weight:8.25 × 12.63 in.; 3.2 kg
- Maximum pressure and warranty:150 psi; five years leak, one year parts
Our verdict“Choose the Rheem RTEX-11 over the ThermoMate when a wider setpoint range and finer temperature adjustment matter more than a lower-demand setup.”
CAMPLUX 6 kW Electric Tankless Water Heater, 240 V
The CAMPLUX is the lowest-output choice in this group, and that is its point: 6 kW for a sink or small household, not for several busy fixtures. Its stated 50°F temperature rise at 1.0 GPM gives a more useful reference for modest flow than the SIVUATEK’s 3.3 GPM figure, which does not state a rise. A 30 A breaker and 10 AWG wire are still substantial hardwired requirements, but they are less demanding than the 50 A and 60 A circuits required by the ThermoMate and SIVUATEK. Touch controls, a temperature display, and self-modulating power make adjustment straightforward. The tradeoff is capacity: its stated 1.5 GPM flow and point-of-use design leave little room for simultaneous shower-and-sink demand.
Pros:- Smaller 6 kW load than the 11–14 kW options in this batch.
- Specified 50°F rise at 1.0 GPM helps set expectations for low-flow use.
- Self-modulating power and touch controls with a real-time temperature display.
- Compact 3.9 lb wall-mounted body with a two-year limited warranty.
Cons:- Requires hardwiring, a 30 A breaker, and 10 AWG wire.
- Its 1.5 GPM listed flow and 6 kW output limit fixture demand.
- Maximum temperature is 131°F.
Best for: People adding hot water to a single sink or other low-flow point who want a small wall-mounted unit and can provide a hardwired 30 A circuit.
Not ideal for: Households seeking a multi-fixture or whole-home heater, especially where simultaneous shower and sink use is expected.
- Power and voltage:6 kW; 240 V
- Flow rate:1.5 GPM
- Temperature rise:50°F at 1.0 GPM
- Maximum temperature:131°F
- Electrical requirement:Hardwired; 30 A circuit breaker; 10 AWG wire
- Water connection:1/2 in. NPT
- Dimensions and weight:10.95 × 7.4 × 2.52 in.; 3.9 lb
- Warranty:Two-year limited
Our verdict“Choose the CAMPLUX for one low-flow sink when modest capacity and a lower circuit requirement matter more than multi-fixture output.”
Rheem RTEX-24 24 kW 240 V Electric Tankless Water Heater
The RTEX-24 is the capacity pick here: its 24 kW output and listed 5.9 GPM flow place it well above the ThermoMate and Rheem RTEX-11, both aimed at point-of-use jobs. Digital controls adjust from 80–140°F in 1-degree steps, and no venting is needed, so it suits buyers replacing a larger electric setup who want on-demand heating. The tradeoff is electrical, not physical: this wall-mounted unit needs three 40 A double-pole breakers, three sets of #8 AWG copper conductors with ground, and a recommended 200 A household service panel. That makes panel capacity and installation planning central to the decision. Its 5.9 GPM figure should not be read as guaranteed at every temperature rise; cold incoming water can reduce usable flow.
Pros:- Highest listed output in this batch at 24 kW and up to 5.9 GPM.
- Digital 1-degree temperature adjustments across an 80–140°F range.
- No venting required and a wall-mounted form.
- Five-year leak and one-year parts warranty.
Cons:- Requires three 40 A double-pole breakers and three sets of #8 AWG copper conductors with ground.
- Recommended 200 A household service and substantial panel space can rule out older or smaller electrical systems.
- Actual flow depends on incoming water temperature and required temperature rise.
Best for: Households with several regular hot-water demands that have a 200 A service panel and room for three dedicated 40 A breaker positions.
Not ideal for: Small homes or point-of-use buyers who lack substantial panel capacity, or anyone seeking a simple single-circuit installation.
- Power and voltage:24 kW; 240 V
- Flow rate:Up to 5.9 GPM
- Temperature range:80–140°F; digital adjustment in 1-degree increments
- Efficiency:99.8%
- Electrical requirement:Three 40 A double-pole breakers; three sets of #8 AWG copper conductors with ground
- Recommended household service:200 A
- Dimensions and weight:17.63 × 18.25 × 3.5 in.; 17.8 lb
- Maximum pressure and warranty:150 psi; five years leak, one year parts
Our verdict“Choose the RTEX-24 for higher multi-fixture demand only if your electrical service can support its three-circuit installation.”
How We Picked
I ranked these 15 heaters by how clearly their stated electrical input and intended scale match common jobs: a single sink, a limited point-of-use application, or broader household demand. I also weighed the usefulness of the published specifications, the practical distinction between product sizes, and whether the listing gives buyers enough information to investigate installation needs. The ranking favors options whose capacity and likely role are easier to interpret, not the largest kW figure by itself.
A 240V connection does not mean every model is interchangeable. Breaker and wire requirements, service-panel capacity, incoming water temperature, and simultaneous fixture use can change which unit is suitable. I treat advertised flow figures as conditional rather than guaranteed, and I rank compact models lower for whole-home ambitions while recognizing their value for targeted use. Before buying, confirm the manufacturer’s electrical specifications and have a qualified installer check the home’s wiring and panel.
Factors to Consider When Choosing Electric Tankless Water Heater 240v
Choosing a 240V electric tankless heater starts with the job it must do, then works backward to the home’s electrical and water conditions. These checks help prevent a common mismatch: buying for a headline flow number without confirming whether the heater can deliver the needed temperature rise at your fixtures.
Match the heater to simultaneous hot-water use
List the fixtures you expect to run at the same time, rather than adding up every tap in the home. A shower and kitchen tap running together create a different demand from one bathroom sink used alone. Tankless output is shared across active fixtures, so a model that serves one location comfortably may provide less flow when another opens. Think about peak routines, such as morning showers, not just average daily use. If demand varies widely, a larger unit may help only if the electrical system and local water conditions support it. For a single remote sink, a smaller point-of-use heater can avoid sizing the entire system around a rare peak.
Calculate temperature rise for your local water
Incoming water temperature changes how much work an electric heater must do to reach a comfortable outlet temperature. Colder groundwater calls for a larger temperature rise, which can reduce the flow a given unit can deliver. This is why a published GPM figure should not be treated as the same result in every region or season. Check local winter water temperatures and use the manufacturer’s performance chart at the temperature rise you expect. A buyer in a mild climate may have more usable flow from a mid-power model than a buyer in a cold climate. If the manufacturer does not publish enough performance detail, ask for it before relying on the unit for multiple fixtures.
Check panel capacity, breakers, and wiring before choosing kW
Electrical demand is a central part of this purchase, not an installation detail to handle after delivery. Higher-kW heaters can call for multiple dedicated circuits, specific breaker sizes, and heavy-gauge wiring; the exact requirements vary by model. A 240V outlet or circuit already in the home does not prove it can support a tankless heater. Have an electrician review the service panel, spare capacity, cable routes, and the manufacturer’s installation instructions before selecting a unit. Upgrading the panel or adding circuits can change the project’s scope. When electrical capacity is tight, a smaller point-of-use model or another water-heating arrangement may make more sense than forcing a high-output unit into the system.
Decide between point-of-use and whole-home placement
A point-of-use heater sits near the fixture it serves, which can reduce the wait for hot water at a remote sink and limit the amount of pipe that must be heated. It is not automatically a whole-home solution, and placing several small units around a house may add wiring and installation complexity. A centrally located heater can serve more than one fixture, but its performance depends on peak demand, pipe layout, and available output. Consider where hot water is wasted while waiting, how far fixtures are from a central unit, and whether the installation location has suitable electrical access. Buyers replacing a storage tank should also check plumbing connections, mounting requirements, and local code rules instead of assuming the swap is direct.
Compare controls, service access, and documentation
Display style and adjustment features matter most when they make setup and troubleshooting easier. Before choosing, check whether the manual explains temperature adjustment, error codes, maintenance, and required clearances in plain terms. A readable display can help with daily changes, but it cannot make an undersized heater deliver more hot water. Confirm the warranty terms, service process, and parts availability from the manufacturer rather than relying on a short product listing. Also check whether the unit needs a filter or periodic descaling in your water conditions. Better documentation and accessible service support may be worth prioritizing over a small difference in stated output.
Account for water quality and maintenance
Hard water can leave mineral scale inside a tankless heat exchanger, reducing performance and increasing service needs. Ask whether the manufacturer specifies flushing intervals, a service valve kit, or water treatment for your water conditions. Maintenance access matters: a heater installed in a cramped location can make routine flushing slower and more costly. If your home has well water, sediment, or unusually hard water, check filtration and maintenance guidance before selecting a model. Skipping maintenance can shorten equipment life or interfere with reliable heating. Choose an installation spot that gives a technician room to inspect and service the unit.
Frequently Asked Questions
Can a 240V tankless water heater replace my existing whole-home heater?
Possibly, but the voltage alone does not determine whether it can serve the whole home. Compare peak simultaneous demand and winter inlet-water temperature against the model’s performance data, then check its circuit and breaker requirements. Many homes need electrical work to support a larger tankless unit, and some service panels may not have enough capacity. Have a qualified electrician and plumber review the proposed installation before removing the existing heater. If the system cannot meet peak demand, a point-of-use unit or a different heating setup may be a better fit.
How much hot-water flow should I expect from the advertised GPM?
Use the advertised GPM as a reference, not a guaranteed flow rate for your home. Actual output depends on the temperature of incoming water and how much it must be heated, as well as the heater’s capacity. Colder water generally means less flow at the same target temperature. Check the manufacturer’s chart for the temperature rise closest to your local conditions, then compare that output with the fixtures you plan to run together. If a listing gives a single flow figure without the conditions behind it, ask the manufacturer for the supporting data.
Can I install one of these heaters on an existing 240V circuit?
Do not assume an existing 240V circuit is sufficient. The heater may require a particular breaker rating, dedicated circuit or circuits, and wire gauge that differ from what is already installed. The circuit must also be checked against the manufacturer’s instructions and local electrical code. A qualified electrician can assess the wiring and the home’s service-panel capacity before purchase. Confirming this first can help prevent a return or an installation that needs unplanned electrical work.
Should I choose one large heater or separate small units for different fixtures?
A central heater can be simpler when fixtures are relatively close and the unit is sized for their combined peak demand. Separate point-of-use heaters can help when a remote sink has a long wait for hot water or when only a small amount of water is needed at that location. Multiple units, however, add electrical connections and may increase installation and maintenance complexity. Compare the distance from the heater to each fixture, how often hot water is used, and the available electrical capacity at each location. The best arrangement depends on the home’s layout, not just the total kW listed across the units.
Is a larger-kW model always the better choice?
No. A larger unit may support more flow or a greater temperature rise, but it also places greater demands on the electrical system and may cost more to install. If the home’s panel cannot support it, the higher capacity on paper will not make the unit a practical choice. A smaller model can be a better match for a single sink or limited demand, while still requiring proper circuit checks. Start with the fixtures you need to serve and local inlet-water conditions, then choose the smallest model that meets that demand within its published performance range.
Conclusion
For a balanced starting point, I’d choose the EcoSmart ECO 11 for modest demand, after confirming its output suits local water conditions. Buyers focused on higher capacity should compare the Stiebel Eltron Tempra 24 Trend and Rheem RTEX-24 only after an electrician verifies the home can support a 24 kW load. For a smaller, targeted job, the ThermoMate 6 kW or CAMPLUX 6 kW is a more relevant category than a large whole-home model; the Rheem 8 kW is another limited-demand option. Beginners should prioritize clear manufacturer documentation and a professional installation review over choosing by GPM headline alone. My best-value direction is to buy only the capacity the intended fixtures need, rather than paying for a larger heater that the home’s electrical system or water conditions cannot fully use.
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