10 Electric Tankless Water Heaters For The Whole House 2021 Reviews

Best electric tankless water heaters. Back as early as the 1870s, an investor named Maughan invented an instant water heater. This invention was the first design of a water heater that influenced the designs of another inventor named Edwin Ruud.

Edwin Ruud was a Norwegian mechanical engineer who invented the automatic storage water heater in the year 1889. Ruud invented the hater for George Westinghouse at the Fuel Gas and Manufacturing Company.

This invention was the first successful patent heated water. There was a problem with the invention where the water was not maximally hot. Eight years later, Ruud improved his invention by adding enclosed burners, copper coil heating tubes, cast-iron shells, a bottom gas heater, and a temperature-controlled gas-valve.

What is a tankless electric water heater?

The space needed by the tankless electric water heater is less compared to storage water heaters because they heat the water directly. At the moment you turn on the water heater, the water flows through a copper pipe or other type of pipe and into the unit. The water then is heated by the electric element inside the unit. This process will supply hot water constantly.

Electric tankless water heaters can heat and supply between 2 to 5-gallons of hot water per minute. Electric tankless water heaters produce lower flow rates than gas water heaters.

For a large number of people in one family, one home would require much supply of hot water. Installing more than one tankless water heater is common. These water heaters is will make sure there is enough hot water for the dishwasher, laundry, and showers.

What are the benefits of a tankless water heater?

  • Efficiency. Homeowners who use forty-one gallons of hot water can get between 24 and 34 percent efficiency when they use a tankless water heater compared to a storage model. The more water you use, the higher number of efficiency.
  • Longer lifespan – Tankless water heaters can last from 20 to 30 years, while storage water heaters last about 10 years.
  • Flexible location. Tankless water heaters or on-demand water heater’s dimensions are small. They can be installed in tight spaces including a small bathroom or small closet or small basement space or can be wall hung near the toilet.
  • Supply a steady stream of hot water. As mentioned above, a tankless water heater will deliver two to five gallons of hot water per minute for as long depending on its flow rate.
  • Instant hot water. Tankless water heaters can supply an unlimited stream of hot water in a few seconds. These water heater units can deliver on their promise to supply hot water without storage tanks.
  • Lower yearly cost. Tankless water heaters can save hundreds of dollars annually compared to storage water heaters.
  • Tankless Federal Tax Credit. Under the Bipartisan Budget Act of 2018, tax credits for all residential renewable energy products have been extended through December 31, 2021. Products eligible for the tax credits are the ones that are energy savers, money savers,s and protect the environment. The federal government offered a 10% tax credit on the overall cost of having a tankless hot water heater at home.
  • Two options. Tankless water heaters are commonly powered by natural gas. The electric models are also popular and available on the market.
  • Have a long warranty. Due to their lengthy lifespan, tankless water heaters commonly have longer warranties. Homeowners will not have to pay for repairs or for a replacement. Many electric models offer warranties up to 20 years, which is the most common lifespan of a tankless heater.

Difference between the tank and tankless water heaters

Electricity24-hoursAs needed
WaterLimited to the size of the tankUnlimited
EnergySome are Energy StarMost are Energy Star
PriceLowMedium to high

How tankless water heaters work?

The concept of tankless water heating is easy to understand. Without heating water and storing it in a storage tank where some energy is lost every day, tankless systems heat water when needed and used. Tankless water heaters are much more powerful and can supply the demands of a whole household as well as many commercial applications compared to previous decades.

A flow sensor detects a signal the minute you turn on your hot water faucet and the sensor activates the tankless water heater. Heating elements inside the water heater heat the water and will only stop until the flow sensor detects a signal that the water faucet is off.

Since the heater only runs for a few minutes per day, a significant reduction in energy costs for as much as 30 to 50% is achievable. A tankless water heater can operate without running out of hot water, the unit does not have to overheat the water anymore. This operation reduces the formation of hard water scales and add another energy savings.

The result would be less sediment build-up and less prone to problems.

Difference between gas and electric tankless water heater

Energy factor0.990.78 – 0.91
MaintenanceLittleInspect annually
InstallationEasyMore complicated
Water supply2 to 5 gallons per minuteMore than 8 gallons per minute
Installation costInexpensiveMore expensive
Water usage efficiencyLowMedium to large
Operational costHigherLow
Lifespan20 to 50 yearsMaximum 20 years
WarrantyMore than 20 yearsMaximum 20 years
Environmental impact98% energy saving85% energy saving
PriceMore expensiveLess expensive

Main components of tankless electric water heater

1. Heating elements

This component is the main source of the heat on the electric water heater. They are located at the lower and upper elements on tall units. Smaller water heater models are commonly equipped with single elements. These heating element parts can be found in heat pumps and solar heating systems. Some water heaters are equipped with the dry-fire feature, to protect the elements if exposed to the air.

2. Coldwater shut off valve

This component shuts the cold water supply down when a water heater requires to be replaced or drained.

3. Hot water outlet

The pipe drops down into the water heater to let the hot water exit the water heater unit to flow into the water supply in a home or commercial building.

4. Elements

Elements are only installed in electric water heaters and they are the means by which heat is transferred to the water. Think of the metal rod in an electric oven same concept.

5. Safety features

  • Overheat sensor. When the unit is overheated, the sensor will shut the unit down. If the hot water is very hot, the unit has to cool down before starting a new operation.
  • Freeze sensor. This temperature limiter will protect the water heater from freezing.
  • Fan speed monitoring. The component will make sure proper fan operation.
  • Water flow sensor. This component will protect the unit from the minimum flow. The unit must get enough water for normal operation.
  • Pressure relief valve. This component is used to protect the system from the excessive water pressure in the system.

Factors to consider when purchasing a tankless electric water heater

1. Flow rate

To discover the amount of hot water required, first, you must list the total number of appliances that you will be used simultaneously. Once in one day, these appliances will have hot water demand such as the kitchen sink, doing a load of laundry, and showering. Next, you add up each individual flow rate of the appliances for the total flow rate.

Read the manual book of each water heater product for the fixture for the flow rate. Check for the GPM stamped on the item. You can use this formula: 60 divided by the number of seconds to fill a 1-gallon container with water from the appliance.

Average GPM usage for appliances

ApplianceGPM Value
Washing Machine (High-Efficiency/Standard)1.0 – 2.5 GPM
Tub4.0 GPM
Shower2.5 GPM
Kitchen Faucet2.5 GPM
Dishwasher (High-Efficiency/Standard)0.5 – 1.5 GPM
Bathroom Faucet2.5 GPM

2. Temperature rise

You need to get this figure by deducting the temperature of the incoming groundwater from the set temperature. The estimation of the average incoming temperature is around 50ºF (10ºC). This will depend on the region or area you live in and what time of year you will be heating your groundwater.

For most of your appliances, the post-tank heated water should be about 120ºF (49ºC). The higher the incoming water temperature, and the lower the set temperature, the more hot water flow will produce by the water heater. The more groundwater is needed to rise to achieve water temperature, the more energy it will take.

The flow rates and temperature rise will vary per appliance and that you should account for different ratios. The following are some average flow rates (GPM) and average desired temperatures for some common household devices.

ApplianceGPM ValueAverage temperature
Washing Machine2.0 GPM120ºF
Tub4.0 GPM102ºF
Shower2.5 – 3.0 GPM104ºF
Kitchen Faucet1.5 GPM110ºF
Dishwasher1.5 GPM110ºF

3. The size

An average shower will be between 104–106°F and uses 2.6 gallons of water. If the water temperature is 40° coming into your small home, and you want to produce enough hot water to run 2 showers at the same time. You must raise the incoming water temperature from 40 degrees to 105 degrees. You have to heat at least 5.2 gallons of water for 2 showers. What you need to buy is a tankless water heater that can heat water at least a 60-degree rise in temperature at 5.2 gallons per minute.

4. Easy installation

The tankless water heater installation should be done by a licensed contractor. They must be trained to understand and handle the plumbing, electrical and venting (if any) aspects of a tankless water heater. If you do it yourself, the installation can cause performance and operational issues.

Best tankless electric water heater reviews

1. Stiebel Eltron Tankless Electric Water Heater

Tankless electric water heater
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This Stiebel Eltron tankless electric water heater comes with an Advanced Flow Control that automatically keeps water temperature constantly. Whenever the water demand exceeds the capacity, the feature will lower the flow.

Save Space

Due to its small dimension (4.63 x 16.63 x 14.5 inches), it can save saves space without sacrificing the supply of endless hot water and without venting needed. Its auto-modulation feature can provide an Eco-friendly unit that saves energy. It is possible because it can control the water flow.

Silent Operation

You can start the water heater easily with silent operation. All you need to do is to switch on the electronic switch that will activate the hot water heater. The unit can show a digital temperature, preset temperature, and memory buttons.


The interior is made of a solid copper heating system with 24kW, 240V, 150 A and delivers an output water temperature of 68°F to 140°F. The tankless electric water heater comes with a 7-year leakage warranty and 3-year parts warranty.

ManufacturerStiebel Eltron
Dimension4.63 x 16.63 x 14.5 inches
kW24 kW
Voltage240 volts
Max. amperage draw100 A
Min. required breaker(s)2 x 50 A DP
Min. required wire size and number of runs2 x 6/2 AWG
Min. recommended household electric service150 A
Min. flow to activate unit0.50 GPM
Water connections3/4″ NPT
Output water temp. range86°F – 140°F
Max temperature rise92°F – 82°F at 1.50 GPM
Weight16.1 lb/7.3 kg
Nominal water volume0.26 gal/1 liter
Max. inlet water temperature131°F/55°C
Working pressure150 PSI/10 BAR
Tested to pressure300 PSI / 20 BAR;
WarrantyLimited warranty

2. Ecosmart ECO 36 36kw 240V Electric Tankless Water Heater

Ecosmart Electric tankless water heater
But At Home Depot
Buy From Amazon

This ECOSMART ECO 36 water heater is suitable for supplying hot water for townhomes, other whole-home applications, apartments, and condominiums. The home device can support between 3.6 and 8.7 GPM.

Flexible Water Temperature

You can add and increase the water temperature by few degrees based on the temperature of the cold water as the water enters the water heater. The home device uses self-modulating technology to adjust the temperature of the water automatically.

Two Temperature Options

When the water temperature drops below 40 degrees Fahrenheit, it can regulate to become hot water and supply two showers with an endless stream of hot water. You can use the knob beneath the screen to regulate the water temperature and provide the option of Celsius or Fahrenheit degree settings.

Dimension3.6 x 21 x 17 inches
kW36 kW
Voltage240 volts
Max. amperage draw33 A
Min. flow to activate unit0.50 GPM
Water connections3/4″ NPT
Output water temp. range377°F -105°F
Max temperature rise92°F – 82°F at 1.50 GPM
Weight18.35 pounds
Max. inlet water temperature77°C
WarrantyLimited lifetime warranty

3. Rheem RETEX-24 Tankless Electric Water Heater

Rheem Electric tankless water heater
But At Home Depot
Buy From Amazon

If you want to get continuous hot water on demand, you can choose Rheem Retex-24 Performance Tankless Electric Water Heater. The heater can help you lower energy usage. The water heater model does not need venting and the size is small for tight space.

Adjustable Water Heater

One water heater unit can supply hot water for up to two faucets and three showers. You can easily adjust this water heater unit.


It comes with a 5-year heat exchanger warranty and a 1-year parts limited warranty.

Elements Material

The immersion heating elements is made of copper with brass top. increases durability and are threaded for easy replacement. It is very easy to install.

Dimension18.25 x 3.5 x 17.63 inches
kW24 kW
Voltage240 volts
Min. flow to activate unit0.50 GPM
Water connections3/4″ NPT
Max. flow to activate unit5.9 GPM
Weight17.8 pounds
Warranty5 years

4. Black and Decker BD-18HD Residential Electric Tankless Water Heater

Black and Decker Electric tankless water heater
But At Home Depot
Buy From Amazon

This Black and Decker BD-18HD Electric Tankless Water Heater comes with smart flow technology to supply an unlimited stream of hot water. The water supply will be automatically open and shut, to reduce water consumption and lower water waste.

Self-Modulating System

The eco-friendly water heater unit features a self-modulating system to regulate the number of energy needed to heat the water. This regulation process will provide savings on your energy bill.


The Black and Decker electric tankless water heater can operate without venting for flexibility to install anywhere inside your tight living space in an apartment or small home. It can supply a showerhead (1.5 GPM), the kitchen sink (1 GPM), and the bathroom sink (0.5 GPM) or 2 shower heads, and a bathroom sink. The inlet temperature is 73°F.

ManufacturerBlack and Decker
Dimension18.4 x 15.7 x 7.5 inches
kW18 kW
Voltage240 volts
Min. flow to activate unit1.50 GPM
Water connections1/2-inch NPT
Max. flow to activate unit3.7 GPM
Weight11.97 pounds
Warranty7-year leakage free, 5-year heat exchanger, 2-year parts

5. Titan SCR-2 Residential Electric Tankless Water Heater

Titan Electric tankless water heater
Buy at Home Depot
Buy At Walmart

Energy Saving

This TITAN Electronic Tankless Water Heater could be used anywhere in the house. You can save your energy cost using this water heater.

Temperature Setting

It can supply hot water temperatures from 105°F to 120°F. This unit can supply a kitchen sink, bathroom, or garage. While in operation, it can reduce hot water costs up to 60% compared to other electric water heaters. It comes with a dedicated digital microprocessor to supply input and output temperatures 21 times per second.

Save Space

It does not occupy floor space, compact, lightweight, and easy to install.

Dimension12 x 10 x 5 inches
kW11.8 kW
Voltage220 volts
Min. flow to activate unit0.50 GPM
Water connections1/2-inch NPT or 3/4-inch NPT
Max. flow to activate unit4 GPM
Weight2 pounds
Warranty10-year limited warranty
CertificationEnergy Saving, UL compliant, and ETL Lead Free Certified

6. Bosch Tankless Electric Water Heater WH27 Tronic 6000 C

Bosch Electric tankless water heater
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This Bosch tankless electric water heater is suitable for the whole house or commercial building due to its compact and powerful features.

Save Space and cost

Its dimension can save spacing and can supply endless hot water supply that can reduce electricity costs.


The water heater is built to last with solid copper heat exchangers, comes with a 5-year leakage warranty, and can lower the energy bill. It is equipped with Polymer encased elements and with a built-in flow sensor to make sure supplying output temperature constantly. It works at 97% thermal efficiency with minimal stand-by loss.

Dimension15.5 x 4.5 x 12.5 inches
kW27 kW
Voltage220/240 volts
Min. flow to activate unit0.80 GPM
Water connections3/4-inch NPT
Max. flow to activate unit2.6 GPM
Weight22 pounds
Warranty5-year leakage warranty

7. Ariston Aures Pro 36 Electric Tankless Water Heater

Ariston Electric tankless water heater
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Compact and Luxurious Design

The Ariston Aures Pro 36 has a luxurious design and compact but powerful enough to supply hot water for the whole appliances. Its size allows for easy installation that can fit into any living space as necessary. The advanced hi-tech display can support water heater management with soft-touch buttons.

Warranty and Maintenance

This water heater can allow easy maintenance with easy access to all internal components. It comes with a 6-year limited warranty and 2-year parts warranty.

Sturdy Materials

Its heat exchanger is made of sturdy copper and the stainless-steel canister can ensure long-lasting quality and high resistance to high water pressure. There is an electronic thermostat that can prevent scalding managed by the overheating prevention features.

Dimension24 x 18 x 16 inches
kW36 kW
Voltage240 volts
Min. flow to activate unit0.80 GPM
Water connections3/4-inch NPT
Max. flow to activate unit7.02 GPM
Weight20 pounds
Warranty6-year limited warranty against leaks, 2-years on parts

8. Eemax EEM24027 Tankless Electric Water Heater

Buy at Home Depot
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The Eemax EEM24027 can supply hot water for up to 2 sinks and 1 shower at the same time in colder climates. For warmer climates, the supply can be up to 4 showers or sinks at the same time.

Save Cost

The great thing about this water heater is that it can save up to 50% of water bills annually. It can supply and endless hot water with the right temperature constantly. Its compact size can save storage space without venting.

Self-Modulating Technology

The patented self-modulating technology can adjust energy depending on hot water requirements. It can last a lifetime due to its durable stainless steel heating elements.

Dimension17 x 17 x 3.75 inches
kW27 kW
Voltage240 volts
Min. flow to activate unit0.25 GPM
Water connections3/4-inch NPT
Max. flow to activate unit4.2 GPM
Weight13.75 pounds
Warranty5 years for leaks and 1 year for parts

9. Atmor AT-29WH-HD Electric Tankless Water Heater

Buy at Home Depot

The ATMOR tankless electric water heater is a convenient, efficient, and Eco-friendly device that provides an endless stream supply of hot water instantly. This water heater can sense the water flow and will automatically turn on and off its supply of hot water.

Intelligent Technology

Its intelligent technology can reduce water consumption, eliminate costs, and save on energy costs. The compact size water heater can give you enough. You can install it against the wall, under the sink, or near the point of use.

Flexibility and Warranty

The Atmor water heater requires no venting for flexibility to install anywhere inside your RV, garage, home, and office. It comes with 7 years leakage warranty and 2 years parts warranty.

Dimension18 x 14 x 4.5 inches
kW29 kW
Voltage240 volts
Min. flow to activate unit2.75 GPM
Water connections3/4-inch NPT
Max. flow to activate unit5.4 GPM
Weight13.75 pounds
Warranty7 years leakage warranty and 2 years parts warranty

10. IHeat S-16 Electric Tankless Water Heater

Buy at Home Depot
Buy At Amazon

The IHeat S-16 Electric Tankless Water Heater Model S-16 can supply 1 sink at 0.50 GPM and 2 showers at 1.5 GPM at the same time with the capacity of heating 3.5 GPM. This IHeat S-16 water heater can power a 3 to 4 bedroom with 2-1/2 bathroom home, including dishwasher and clothes washer.


It is designed to heat incoming water at inlet water temperatures and a maximum output temperature based on simultaneous use. By the time the demand for hot water decreases, the output water temperatures will increase.

Save Cost and Warranty

This water heater can save up to 60% on water heating costs. It comes with 3 year internal electrical components, and 5 year due to leaks limited warranty.

Dimension11.5 x 9 x 4.5 inches
kW16 kW
Voltage240 volts
Min. flow to activate unit0.75 GPM
Water connections1/2-inch NPT
Max. flow to activate unit2 GPM
Weight7.5 pounds
Warranty3 year internal electrical components, and 5 year due to leaks limited warranty

Best tankless electric water heater comparison chart

ProductMax GPMWater connectionkWVoltage
Stiebel Eltron Tankless Electric Water Heater4.5 GPM3/4″ NPT24 kW240 volts
Ecosmart ECO 36 36kw 240V Electric Tankless Water Heater8.7 GPM3/4″ NPT36 kW240 volts
Rheem RETEX-24 Tankless Electric Water Heater5.9 GPM3/4″ NPT24 kW240 volts
Black and Decker BD-18HD Residential Electric Tankless Water Heater3.7 GPM1/2″ NPT18 kW240 volts
Titan SCR-2 Residential Electric Tankless Water Heater4 GPM1/2″ NPT or 3/4″ NPT11.8 kW220 volts
Bosch Tankless Electric Water Heater WH27 Tronic 6000 C2.6 GPM3/4″ NPT27 kW220/240 volts
Ariston Aures Pro 36 Electric Tankless Water Heater7.02 GPM3/4″ NPT36 kW240 volts
Eemax EEM24027 Tankless Electric Water Heater4.2 GPM3/4″ NPT27 kW240 volts
Atmor AT-29WH-HD Electric Tankless Water Heater5.4 GPM3/4″ NPT29 kW240 volts
IHeat S-16 Electric Tankless Water Heater2 GPM1/2″ NPT16 kW240 volts

Choosing the suitable plumbing system for your water heater

1. Hot water flow

Every homeowner likes to shower with hot water in the morning or evening. All you need to do is to turn on the tap and the supply of hot water is there.

What makes this possible is the plumbing system is connected to the water heater. The water heater has two pipes. The first pipe supplies the cold water, and the second one transfers the hot water to the appliances.

2. Re-calculate plumbing system

The method of re-circulation is used for fast hot water delivery which uses a two-pipe system. The first pipe gets the water from the heater to the sinks. The second one takes the unused water to the heater all over again.

The method keeps the water circulating through the plumbing system using the circulation pump. At the same time, these pipes are insulated to keep the water heated longer. It is possible if the water is running through space at a lower temperature.

3. Tank system

This plumbing system is utilized to supply hot water fast. There is a small heater is installed at the point of used to ensure instant delivery.

The pipes for the tank systems come down to pipes that go from the heater to the tank and from the tank to the sinks. This system uses a lot more energy, increasing fuel requirements, and increase monthly costs.

Types of water pipes

1. Copper pipes

The copper pipes has been used for over 40 years due to its reliability and resistant. Copper pipes are resistant to chemicals and other contaminants. Corrosion has rarely occur, while it performs an excellent results in delivering hot water.

Using it for heating water lines is an excellent choice. Unfortunately, it costs more initially and it costs more to install. Copper is perfect for auxiliary plumbing systems in water heaters, producing perfect heating performance. It is recommended for a new installation.

2. Galvanized steel

The galvanized steel pipe is one of the standard materials used for house plumbing systems. It works excellent for water heaters but it is more prone to rusting. Galvanized steel pipes can last longer than copper which is up to 100 years.

3. PEX

PEX pipe is made of polybutylene mixed with polyethylene. It is flexible which makes it easy to install. It will keep the groundwater working efficiently, but when used for a water heater, it could be affected by the high temperature.

4. PVC

PVC is plastic and it is highly versatile, durable, and reliable. It is cheaper than most options. The PVC pipes are less expensive than steel, copper and even PEX.

The problem is, PVC can create much more contaminants inside, and less resistant to hot water. The maximum operating temperature is 140F. If PVC pipe is your choice, you use it on a re-circulating system.The suitable use for PVC would be alongside steel or copper.