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Top 10 Best tankless hot water heater electric Reviews

Top 10 Best tankless hot water heater electric in 2021 Comparison Table

SaleBestseller No. 1
EcoSmart ECO 11 Electric Tankless Water Heater, 13KW at 240 Volts with Patented Self Modulating Technology
  • Endless On-Demand Hot Water; Consistent hot water when you need it that never runs out; Continuously monitored water temperature and controlled flow rates ensure efficiency and consistent performance within 1 degree of selected temperature
  • Save Space; EcoSmart tankless electric water heaters are 90% smaller than traditional tank heaters; may be installed on wall or at point of use; Dimensions 11.5 x 8 x 3.75 inches
  • Save Energy; EcoSmart tankless electric water heaters are 99% thermal energy efficient; Only heats water when called unlike a tank heater that maintains water temperature even when not being used.
  • EcoSmart ECO 11 Sizing; 13-kilowatt tankless electric water heater ideal for providing hot water for a bathroom, small sink, office breakroom and other point-of-use or low-flow applications; provides between 1.3 and 3.1 gallons-per-minute depending on the inlet water temperature; refer to the sizing guide to select the proper solution
SaleBestseller No. 2
EcoSmart ECO 27 Electric Tankless Water Heater, 27 KW at 240 Volts, 112.5 Amps with Patented Self Modulating Technology,White
  • Savings of up to 50% on water heating costs. Dimensions :17H x 17W x 3.625D inches ;Pipes fittings :3/4 inch NPT
  • Digital temperature control in 1-degree increments allows control of hot water; Activation Flow: 0.3 GPM
  • Copper and stainless components designed for efficiency, durability and easy replacement.
  • Compact size saves valuable storage space, while the stylish and advanced design is pleasing to the eye and Copper and stainless components designed for efficiency, durability and easy replacement.
  • Prior to purchase & installation, please verify that this model is the right size for your hot water needs and electrical requirements. Electrical requirements: 27 kW, 240 volts, (3) 40 required breakers, 112.5 maximum power (AMP), (3) 8 required wire.Amperage Draw:113 A
SaleBestseller No. 3
Rheem RTEX-18 18kW 240V Electric Tankless Water Heater, small, Gray
  • External digital thermostatic control with LED display (+/1 degree accuracy)
  • Most advanced self-modulation, adjust power to meet hot water demand
  • Durable Copper immersion two heating elements, field Serviceable. Flow Rate- up to 4.4 GPM
  • Simple installation – bottom 3/4 inch NPT water connections
  • Threaded for easy replacement, simple installation, digital temperature display
Bestseller No. 4
Rheem RTEX-24 24kW 240V Electric Tankless Water Heater, Gray
  • ON/OFF Dial Control with adjustable digital temperature display
  • Self-modulating power control
  • 24kW Model Flow Rate: up to 5.9 GPM for RTEX-24
  • Bottom 3/4" NPT water connections
  • On demand, consistent and continuous hot water
Bestseller No. 5
Rheem 240V Heating Chamber RTEX-13 Residential Tankless Water Heater, GRAY
  • External adjustable digital thermostatic control with LED display (+/1 degree accuracy
  • Durable Copper immersion two heating elements, field Serviceable.Self-modulating power control
  • Simple installation – 1/2 NPT adapters included; side 1/2 inch Compression water connections
  • 99.8% energy efficient. External controls to adjust temperature in increments of 1°f. Water-Saver Shower Head – 1.5 GPM
  • Threaded for easy replacement, simple installation, digital temperature display 54 A. 13kW Model Flow Rate: up to 3.17 GPM
SaleBestseller No. 6
Stiebel Eltron Tankless Water Heater – Tempra 24 Plus – Electric, On Demand Hot Water, Eco, White, 20.2
  • CONTINUOUS FLOW – Advanced Flow Control patented technology invented by Stiebel Eltron, automatically maintains water temperature for constant comfort. It’ll reduce flow slightly if hot water demand exceeds capacity. Hot showers will never be interrupted again
  • SPACE & ENERGY SAVER – Its small, sleek white design saves space yet still provides endless hot water for your whole house, and no venting is required. Eco friendly unit saves energy with auto-modulation and the ability to electronically control water flow. Savings monitor even shows how much you save on energy costs
  • EASY OPERATION – Electronic switch activates the hot water heater and it’s noise free while in use. Has a digital temperature display and preset temperature and memory buttons, while the interior solid copper heating system does all the power work
  • TEMPRA 24 PLUS – This specific model is 24kW, 240V, requires a min recommended electric service of 150 A, and offers an output water temperature of 68° to 140°F. Check our guides below to compare features of our various Trend and Plus models, each available in different kW levels
  • WARRANTIES INCLUDED – Stiebel Eltron’s top-rated electric tankless water heaters perform with the highest standards for comfort and reliability. Our 7-Year Leakage and 3-Year Parts Warranties are included with purchase
SaleBestseller No. 7
Ecosmart POU 3.5 Point of Use Electric Tankless Water Heater, [email protected], 7” x 11” x 3”
  • Can provide hot water for one sink at 0.5 GPM in warmer climates
  • Requires 1 x 30 amp breaker and 10 AWG wire
  • For one sink at 0.5 GPM in colder climates the POU 6 is recommended
  • Amperage Draw 29 amp. kW - 3.5 kW
  • Connection Fittings 1/2" NPT
SaleBestseller No. 8
EcoSmart 8 KW Electric Tankless Water Heater, 8 KW at 240 Volts with Patented Self Modulating Technology
  • The product is highly durable
  • The product is easy to use
  • Manufactured in China
  • Heating elements are durable and are threaded for easy replacement
  • Activation Flow - 0.3 GPM
Bestseller No. 9
Ecosmart ECO 24 24 KW at 240-Volt Electric Tankless Water Heater with Patented Self Modulating Technology, 17 x 17 x 3.5
  • Lifetime warranty
  • Save up to 60-percent on your water heating cost with an ECOSMART electric tankless water heater
  • Never run out of hot water with an ECOSMART tankless water heater
  • Patented Self Modulating Technology and design.Activation flow 0.3 GPM
  • ECOSMART tankless water heaters are 99.8-percent energy efficient
SaleBestseller No. 10
Ecosmart ECO 36 36kw 240V Electric Tankless Water Heater
  • Sleek and compact design with digital output temperature display
  • ECOSMART tankless water heaters are 99.8-percent energy efficient
  • Manufactured in United States
  • Pipe Fittings:3/4 inch NPT
  • Required Breaker:4 x 40 A
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Our Best Choice: Sio Green SIO14 v2 Infrared Electric Tankless Water Heater – Instant Hot Water Heater – Corrosion Free – Free Maintenance – 220v – 240v / 60A / 14W

Our rating:4.6 out of 5 stars (4.6 / 5)


Product Description


Previous technology, which accounts for a majority of the homes today, will heat a tank full of water from the inside with metallic heating elements. The elements eventually corrode and efficiency decreases rapidly. This leads to high electricity bills, unhealthy water, and expensive equipment costs for maintenance or product replacement. In most electric tankless designs, water flows past heating coils to produce the on-demand hot water, rather than keeping it stored. However, the results are still the same.

Our Engineers first decided on a completely no metallic heating tube, that would be resistant to corrosion, hard water deposit build up and could inject heating BTUs into to water as it passed through the heat exchanger. Their choice of media to use was Quartz. Not only is there an abundant supply of Quartz worldwide, it is also recyclable! Quartz heating tubes have been used for many years because of its rapid thermal properties and stability after many years of use without any deterioration. A patented coating was applied to the outside of the Quartz tubes to reflect or contain the Far-Infrared Energy to heat cold water as it passed through the heating chambers. Far-Infrared energy is safe and is known to condition hard water deposits.

What is Quartz Element and Far Infrared Ray?

Infrared Tankless Water HeaterInfrared Tankless Water Heater

Tech Specs

Quartz Elements

No Maintenance required

No Corrosion

No Calcium Deposits (ideal for hard water area)

Superior Heating Efficiency

Operational Longevity

No Venting Required

Environmentally Free

Recyclable Materials

Far Infrared Ray & Quartz Elements

Far infrared heating technology has been developed by NASA for decades, and quartz tubes are used for various high temperature applications. The process of combining carbon coating heating element technology on quartz tubes to generate far infrared energy to heat water and amplifies far infrared energy inside the quartz tube.

The benefits of Quartz Elements


No more routine flushing to maintain some level of the efficiency and since you don’t have to replace the heating elements periodically, it will save you both time and money!

No Corrosion & No Calcium Deposits

The systems energize your water with quartz elements that create heat without requiring direct contact of metal for heating with the water and minimizes your chances of corrosion accumulating in the water.


commercial residential infrared tankless water heatercommercial residential infrared tankless water heater

Series Parallel HybridSeries Parallel Hybrid

Automatic Modulating Technology

In Automatic mode, the software is using smart modulating technology and formula to calculate the difference between the desired temperature and current temperature, then predicts how much power it requires to ensure the process temperature remains as close to the set point as possible.

Temperature Adjustment

Our premium Sio14 designed for high performance usage in Residential operating 24h/a day for 365 days a year.

Quick & Easy Installation

If you require unlimited hot water, the Sio14-Residential can be installed as in Series, Parallel and Hybrid mode, delivery higher flow rate for higher demand.

See the color chart of North America to find the average incoming water temperature in your region.

IR30 IR30

Choose Your Inlet Ground Water Temperature

Temp rise @ Flow Rate for Sio14 (max power):

30ºF @ 3.0 GPM40ºF @ 2.8 GPM50ºF @ 2.3 GPM60ºF @ 2.0 GPM

For example:

Average cold inlet region 67ºF + temp rise 40ºF @ flow rate 2.8 GPM = 107ºF Outlet Average cold inlet region 72ºF + temp rise 30ºF @ flow rate 3.0 GPM = 102ºF Outlet


240v/Min Panel 150A2 x 30A Double Pole Breakers2 set of pairs 2 #10 AWG WireHard Wiring3/4″ Water Connection NPT

Manufacturer Cover: This unit is qualified One-to-One Replacement Cover service contract (“Replacement Cover”) provides for the replacement of the Product purchased by you if found to be defective during the term of two (2) year(s) from the date of purchase. When the Product failure occurs due to an electrical or mechanical defect, You will receive a replacement product of like kind, quality and value (same condition). Once the Product has been replaced, the cover will carry on the rest of the period from the date of original purchase. Notwithstanding the foregoing time period, the Heat Exchanger portion of the product shall have an additional Eight (8) year limited cover beginning at the expiration of the above two (2) year One-to-One Replacement Cover. This means that, the Product will have a total cover of ten (10) years stated from the date of Sales Invoice/Receipt of the Product, subject to payment of the applicable fee, shipping fee for the Replacement Cover selected. Contact SioGreen to execute this Replacement




Cold Inlet 37ºF-51ºF

Cold Inlet 52ºF-61ºF

Cold Inlet 62ºF and Above

IR30 v2 POU

1 Sink Low-Flow (Require use with 0.5 GPM faucet aerator included)

1 Sink Low-Flow (Require use with 0.5 GPM faucet aerator included)

1 Sink Low-Flow (Require use with 0.5 GPM faucet aerator included)

IR260 v2 POU

1 Sink Low-Flow (Require use with 0.5 GPM faucet aerator included)

1 Sink Low-Flow (Require use with 0.5 GPM faucet aerator included)

1 Sink High-Flow

SIO14 v2

1 Shower Low-Flow (recommend use with 1.5 GPM shower-head)

1 Shower High-Flow

2 Showers High-Flow

SIO18 v2

2 Showers Low-Flow

2 Showers High-Flow

2 Showers & 1 Sink Low-Flow






Max Amperage/Voltage





Max Required Breaker

1x 30A on Power 4 or 1x 20A on Power 3

1x 30A Double Pole on Power 4 or 1x 20A Double Pole on Power 3

2x 30A Double Pole

2x 40A Double Pole

Min. Wire Gauge

1x 10 AWG

2x 10 AWG

2 pairs x 10 AWG

2 pairs x 8 AWG

Water Connections

1/2″ NPS (1/2″ NPT adapters included)

1/2″ NPS (1/2″ NPT adapters included)

3/4″ NPT

3/4″ NPT

Auto Modulating Technology



Temp. rise @ flow rate

30ºF @ 0.8 GPM 40ºF @ 0.7 GPM 50ºF @ 0.6 GPM 60ºF @ 0.4 GPM

30ºF @ 1.5 GPM 40ºF @ 1.2 GPM 50ºF @ 1.0 GPM 60ºF @ 0.8 GPM

30ºF @ 3.0 GPM 40ºF @ 2.8 GPM 50ºF @ 2.3 GPM 60ºF @ 2.0 GPM

30ºF @ 4.0 GPM 40ºF @ 3.6 GPM 50ºF @ 3.0 GPM 60ºF @ 2.5 GPM






What’s included

IR30 v2 POU, 1.5 feet power core, Outlet Flow Gate Valve Adjuster, Flow Limited Aerator Sink, Wall Mount Bracket, Instruction Manual

IR260 v2 POU, Outlet Flow Gate Valve Adjuster, Flow Limited Aerator Sink, Wall Mount Bracket, Instruction Manual

Sio14 v2, Wall Mount Bracket, Instruction Manual

Sio18 v2, Wall Mount Bracket, Instruction Manual

✔PLEASE CALL US FOR SIZING CORRECTLY FOR YOUR UNIT 1 (888) 270-8452 . HOT WATER ANYTIME YOU WANT WITHOUT ANY HASSLE! The Sio Green premium tankless water heater is here to help you enjoy your hand wash or wash the dishes with warm water anytime you want without any fuss. The infrared heating design will heat ONLY the water you use, thus allowing you to save time and money!
✔PATENTED TECHNOLOGY, NO COIL METALLIC ELEMENTS, NO CORROSION, NO MAINTENANCE! That’s right! Our tankless hot water electric heater will create heat without direct contact with metals, which will in turn prevent corrosion, limescale deposit and calcium buildup. As a result, you will have to spend $0 on maintenance or replacements!
✔SAVE YOUR BATHROOM OR KITCHEN SPACE WITH OUR COMPACT WATER HEATER, which is not only ideal for small bathrooms, kitchens or cabinets, but can be also installed easily. The ergonomic size and simple yet innovative construction will allow you to install it almost anywhere, including hotels, stores or restaurants!
✔ADJUST IT TO YOUR EXACT NEEDS EFFORTLESSLY! Our electric tankless hot water heater features Automatic Power Technology so you can easily tailor its performance to your family’s needs and saving the energy and only use what you need, which is ideal for any home application.
✔100% SATISFACTION OR YOUR MONEY BACK! That’s our guarantee! If you are not 100% satisfied with your budget-friendly, space-saving and ultra-practical tankless water heater within 30 days, we will offer you a refund or a replacement. No questions asked! What are you waiting for? Get yours now while supplies last!

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