12 Best Electric Tankless Water Heaters

The best electric tankless water heaters are a great alternative to your energy-guzzling geyser. They use less power, saving money and lowering your carbon footprint.

However, searching the market for an efficient ETWH can be frustrating and confusing. Most manufacturers use jargon you might not understand, or perhaps you’re unsure which size is best for you.

Well, worry not; we’ve compiled this list of the 12 best electric tankless water heaters to help you out! Our experts have gathered all the information you’ll need and packaged it into a helpful buyers guide.

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Best Electric Tankless Water Heaters – Climatebiz Expert Choice

Below are the best electric tankless water heaters:

  • EcoSmart ECO 36
  • Thermoflow Elex 12
  • EcoSmart POU 6
  • Stiebel Eltron Tempra 36 Plus
  • EcoSmart ECO 11

How To Choose The Best Electric Tankless Water Heater

When choosing the perfect ETWH for your home, you must consider the flow rate.

The flow rate refers to the amount of hot water (in gallons) flowing through the ETWH per minute. Each plumbing fixture in your home has a different flow rate. For example, a bath requires 4 GPM (gallons per minute) while a sink requires 1.5 GPM.

The other factor to consider is whether you’d want to install a point-of-use or whole-house system — we’ll dive into the differences between the two shortly.

You may be worried about an ETWHs insane electrical consumption; they can consume 25 kWh of electricity when in use, which is a 400% increase over a tank storage heater. While this may scare you, ETWHs use 30% – 50% less electricity in the long run than a conventional geyser. Why? Because an ETWH only uses electricity when the faucet is open, whereas geysers continuously keep the water warm.

Now let’s determine the best electric tankless water heaters for your home and what flow rate you’ll need.


Electric Tankless Water Heater Types

A point-of-use system, also known as a single-point unit, is installed at each plumbing point or in series. For instance, you may have one ETWH for each bathroom, one for your sink, and one for any other hot water outlet, or install them together.

Single-point electric tankless water heaters are particularly good at supplementing your current water heating system.

A whole-home system means water flows through one larger ETWH and supplies your whole plumbing system. These are the best electric tankless water heaters for existing homes as it replaces your current geyser.

Key Difference Between The Two

Single-point units are much smaller than whole-home systems. Point-of-use systems are physically smaller and can be installed anywhere. Whole-home systems are larger and require more space – you won’t be able to hide one under your kitchen sink.


Electric Tankless Water Heater Flow Rate

The flow rate of your ETWH determines how much water it can heat to your desired temperature. The rate is measured in gallons per minute and determines which electric tankless water heater is best for your home.

Here are the steps you’ll need to follow to work this out:

  • Determine which fixures require hot water
  • Figure out your maximum GPM requirement
  • Establish your temperature rise

It’s not like us to throw you into the deep end so let’s walk you through this process.

Step 1: Determine Which Fixtures Require Hot Water

Time to do a plumbing check on your home. Which fixtures require hot water? The obvious ones include shower heads or a kitchen sink.

Here’s a list of common fixtures that require hot water:

  • Showers
  • Baths
  • Kitchen Sinks
  • Bathroom Sinks

You’ll need to check whether your clothes washing machine uses hot water or not. Newer models only use cold water and heat the water internally. The same goes for dishwashers.

In our example, we’ll use a large home for a family of four with the following fixtures:

  • 2 x showers
  • 1 x bath
  • 3 x bathroom sinks
  • 1 x kitchen sink
  • 1 x Laundry Basin
The floor plan of the house we’ll use in our example.

Step 2: Figure Out Your Maximum GPM Requirement

Now let’s calculate how much water your home will use. Remember that you must overestimate your amount of water usage. Working with minimums might lead you to having no hot water at peak usage.

Here are some gallon per minute values from the U.S. Department of Energy:

FixtureGallons Per Minute
Showers2
Baths4
Bathroom Sinks0.5
Kitchen Sinks2
The table above shows the GPM for different plumbing fixtures around a house.

If you have washers that use hot water, here are the values you’ll use:

ApplianceGallons Per UseCycle Length(minutes)
Dishwashers5.490
Clothes Washers2550
Older washers require hot water to operate.

Now let’s apply these to your example home. Let’s say that you’ll use two showers, the kitchen sink, and a dishwasher simultaneously at peak usage.

Shower 1 (2) + Shower 2 (2) + Kitchen Sink (2) = 6 GPM

This means that your ETWH needs to heat 6 gallons of water per minute during peak usage. However, this only applies if you have a whole-house system. Single-point system usage will be determined per room.

For example, a single-point unit for the one bathroom would only need to heat 2 gallons per minute. Additionally, a single-point unit for the kitchen would need to heat 2.06 GPM (Sink + Dishwasher).

Calculating the difference between the systems is helpful if you cannot find or afford a whole-house system.

Step 3: Establish Your Temperature Rise

The last step is to find the difference between the groundwater input and the hot water output. The temperature rise will tell us how much the ETWH needs to heat the water to reach your desired temperature.

According to the U.S. Consumer Product Safety Commission, your water temperature should be between 104ºF and 120ºF. Therefore, we’ll use 110ºF as the average in this example.

The average water inlet temperature is around 40ºF; your geographical location will determine your groundwater temperature. For example, areas in the southern U.S. will have warmer groundwater temperatures, whereas colder places like Alaska have inlet temperatures of just above 32ºF.

The temperature rise is the difference between the output and input temperatures. Using the average inlet temperature, our household that desires a 110ºF output temperature requires a temperature rise of 70ºF.


Summary

Our example home uses 6 gallons per minute at peak capacity. And we’ve now calculated that our ETWH will need to warm the water by 70ºF.

In conclusion, you’ll need a whole-house ETWH that can produce a 70ºF rise in temperature at 7.03 GPM.


12 Best Electric Tankless Water Heaters

Without further delay, here’s our list of the top 12 best electric tankless water heaters, according to our experts.

Throughout this section, we’ll use an average inlet temperature of 52ºF.

01. Stiebel Eltron Tempra 36 Plus

The Stiebel Eltron Tempra 36 Plus is one of the industry’s best electric tankless water heaters. It comes with a feature exclusive to the Tempra Plus range — Advanced Flow Control™.

The feature activates when the demand for hot water is higher than the heater can produce. The heater will then catch up to the demand by ever-so-slightly increasing the flow. As a result, your shower will never run cold.

In addition, the ETWH has two temperature presets, allowing you to switch between them for summer or winter easily.

Sizing

The Tempra 36 Plus can heat 4.6 gallons of water at a temperature increase of 53ºF. That’s equivalent to three showers and a sink.

In warmer climates, the ETWH can heat a whopping 7.5 GPM. As a result, your household can take four showers and run multiple taps simultaneously. These flow rates make the Tempra 36 Plus the best whole-home electric tankless water heater.

The internal layout of the Tempra 36 Plus.
The internal layout of the Tempra 36 Plus.

Dimensions

Height14-1/2 Inches
Width16-5/8 Inches
Depth4-5/6 Inches
Water Connection3/4 NPT
Weight19 lbs
Dimensions will help you decide where to install the ETWH.

Specifications

kW36
AMPS3 x 50 A
Rec. Breaker Size(3 x 50)A
Voltage240
Rec. Wire Size (CU)3 x 8/2 AWG
Min. Flow (GPM)0.77
Max Flow (GPM)7.5
Specs for the Tempra Plus 36

Warranty 

The Tempra Plus 36 has a 7-year warranty for leaks and a 3-year warranty for parts.


02. Bosch Tronic 3000

The Bosch Tronic 3000 is perfect for guest bathrooms. It’s 98% efficient, and you can install it in any direction. In addition, the 360º installation options allow you to fit the Tronic 3000 under any counter.

It uses a copper heat exchange to ensure no heat is lost while turned on, prolonging its lifespan.

Sizing

The Tronic 3000 best suits smaller bathrooms, such as guest bathrooms. It’s the best electric tankless water heater where a point-of-use system is more practical.

Dimensions

Height6 Inches
Width12 Inches
Depth2 Inches
Water Connection1/2 NPT
Weight– lbs
Dimensions will help you decide where to install the ETWH.

Specifications

kW9.5
AMPS40 A
Rec. Breaker Size
Voltage240
Rec. Wire Size (CU)8 AWG
Min. Flow (GPM)0.3
Max Flow (GPM)1.4
Specs for Tronic 3000.

Warranty 

Comes with a limited 5-year warranty.


03. Thermoflow Elex 12

The Thermoflow Elex 12 is one of the best tankless water heaters for apartments or guest rooms. Its compact and sleek design makes it perfect for an en-suite bathroom.

The Elex 12 allows you to change the temperature in increments of 1ºF, from 32ºF to 140ºF.

Sizing

The Elex 12 has a maximum flow rate of 2.88 gallons at a temperature rise of 77ºF. So it’s perfect for an apartment with two people.

Its best suited for climates with an inlet temperature of 52ºF – the flow rate decreases in colder climates.

We don’t recommend using the Elex 12 for more than one bathroom as it won’t meet your demand. Instead, it would be best to install one in each bathroom.

Dimensions

Height13.6 Inches
Width7.9 Inches
Depth4.8 Inches
Water Connection1/2 NPT
Weight5.4 lbs
Dimensions will help you decide where to install the ETWH.

Specifications

kW36
AMPS50 A
Rec. Breaker Size1 x 2-Pole 60A
Voltage240
Rec. Wire Size (CU)8 AWG
Min. Flow (GPM)0.3
Max Flow (GPM)2.88
Specs for the Elex 12.

Warranty 

The Elex 12 has a 1-year warranty policy.


04. Stiebel Eltron DHC-E

The Stiebel Eltron DHC-E is a compact ETWH for both single and multi-point use.

It’s one of the most flexible electric water heaters with a temperature range of 86 – 140 ºF.

While 120ºF is the suggested max for residential use, the DHC-E can reach 140ºF for commercial use.

You may not be able to adjust the temperature by 1ºF, but it’s user-friendly.

 

Sizing

In a cold climate, the DHC-E can heat water up to 110ºF and supply a shower and multiple sinks. This makes the DHC-E one of the best electric tankless water heaters for whole-house use.

With an inlet temperature of 62ºF, the DHC-E can heat enough water for two showers, hand basins, and a kitchen sink. That’s perfect for your rush-hour morning routine.

The internal layout of the DHC-E.
The internal layout of the DHC-E.

Dimensions

Height14-3/16 Inches
Width7-1/8 Inches
Depth4-1/8 Inches
Water Connection1/2 NPT
Weight5.9 lbs
Dimensions will help you decide where to install the ETWH.

Specifications

kW12
AMPS50 A
Rec. Breaker Size50A
Voltage240
Rec. Wire Size (CU)8 AWG
Min. Flow (GPM)0.264
Max Flow (GPM)4.5
Specs for the DHC-E

Warranty 

Includes a 3-year parts warranty.


05. EcoSmart POU 6

The EcoSmart POU 6 is one of the best electric tankless water heaters for RVs or boats. This point-of-use ETWH uses 5.5 kW and has a compact design, allowing it to fit under your sink.

However, the POU 6 is not a multi-application ETWH. It is designed to only heat enough water for one or two sinks at peak usage. It also has a set temperature of 105ºF that cannot be changed.

The POU 6 comes with a 0.5 GPM sink aerator to ensure it can heat your water effectively.

Sizing

The POU 6 has a maximum flow rate of 1.5 GPM with a 25ºF temperature rise. Its restricted flow prevents you from using it for anything other than bathroom/kitchen sinks. However, if you’re using it for a boat or RV, perhaps that’s all you need.

If you’re using one sink, it has a flow rate of 0.5 GPM and a temperature rise of 75.1ºF.

Internal layout of EcoSmart POU 6.
The internal layout of EcoSmart POU 6.

Dimensions

Height7 Inches
Width11 Inches
Depth3 Inches
Water Connection1/2 NPT
Weight4 lbs
Dimensions will help you decide where to install the ETWH.

Specifications

kW5.5
AMPS25 A
Rec. Breaker Size25A DP
Voltage220
Rec. Wire Size (CU)10 AWG
Min. Flow (GPM)0.3
Max Flow (GPM)1.5
Specs for the POU 6

Warranty

Comes with a 1-year limited warranty.


06. EcoSmart ECO 11

The middle child of the EcoSmart range, the ECO 11 is perfect for single-point applications. For instance, you can use it for your entire RV bathroom, a small washroom in your home, or a guest bathroom.

The ECO 11 is best suited for warmer climates but can be used for kitchen sinks in colder regions.

Sizing

The Eco 11 is perfect for bathrooms in warmer climates or hand washing in colder climates. It has a maximum of 3.1 GPM in warmer climates and 1 GPM in cold climates. But, again, it all depends on where you live.

The temperature can be changed in 1ºF increments and has a maximum of 105ºF.

The internal layout of the ECO 11.
The internal layout of the ECO 11.

Dimensions

Height11.5 Inches
Width8 Inches
Depth3.75 Inches
Water Connection1/2 NPT
Weight6.5 lbs
Dimensions will help you decide where to install the ETWH.

Specifications

kW11/13
AMPS54 A
Rec. Breaker Size60A DP
Voltage220/240
Rec. Wire Size (CU)6 AWG
Min. Flow (GPM)0.3
Max Flow (GPM)3.1
Specs for the ECO 11

Warranty 

Comes with a limited lifetime warranty.


07. EcoSmart ECO 36

These tankless water heaters are designed for larger homes and apartments. They can supply hot water for a single-family, heating up to two showers at a time.

You can adjust the temperature in 1ºF increments with a maximum temperature of 105ºF. It has an activation flow of 0.3 GPM which meets the industry standard.

Lastly, you can replace each part of the EcoSmart ECO 36 at prices ranging from $30 – $40.

Sizing

In warmer weather, the ECO 36 can heat 7.4 gallons per minute. However, it can only maintain a temperature of 105ºF for 3.6 GPM if you live in a cold climate.

The number of gallons the ECO 36 can heat per minute depends on the temperature of the inlet water. For example, if your inlet temperature is 57ºF, it can heat water for two showers and a sink (5.1 GPM).

The internal layout of the ECO 36.
The internal layout of the ECO 36.

Dimensions

Height17 Inches
Width21 Inches
Depth3.75 Inches
Water Connection3/4 NPT
Weight17.4 lbs
Dimensions will help you decide where to install the ETWH.

Specifications

kW36
AMPS150 A
Rec. Breaker Size(4×40)A
Voltage240
Rec. Wire Size (CU)(4) 8 AWG
Min. Flow (GPM)0.3
Max Flow (GPM)8.0
Specs for the ECO 36

Warranty 

The ECO 36 has a lifetime limit warranty. You can also buy new parts from the manufacturer if needed.


08. Rheem Professional Classic Series: RTEX-36

The Rheem Professional Classic Series: RTEX-36 is one of the best electric tankless water heaters for your whole house. With a compact digital control, the RTEX-36 allows you to adjust the temperature in increments of 1ºF. However, the standard temperature is 120ºF.

It’s also important to note that the RTEX-36 offers water pressure of between 25 – 150 PSI. 

The ETWH will only turn on when there is a flow of 0.3 GPM. Luckily, most appliances use 0.5 GPM and above. 

Sizing

The RTEX-36 is suitable for your entire home, reaching a 70ºF temperature increase at 3.0 GPM. Additionally, it has a 62º temperature rise at an average usage of 4.0 gallons per minute.

In addition, the RTEX-36 has a max flow rate of 8.0 GPM. While this rate won’t heat up your water for a shower, it will still provide you with warm water. In addition, the temperatures will be suitable for hand or dishwashing. 

The internal layout of the RTEX-36.
The internal layout of the RTEX-36.

Dimensions

Height18-1/4 Inches
Width21-5/8 Inches
Depth3-1/2 Inches
Water Connection3/4 NPT
Weight22.7 lbs
Dimensions will help you decide where to install the ETWH.

Specifications

kW36
AMPS150 A
Rec. Breaker Size(4×40)A
Voltage240
Rec. Wire Size (CU)8 AWG
Min. Flow (GPM)0.3
Max Flow (GPM)8.0
Specs for the RTEX-36

Warranty 

The warranty period is 5 years for the heating chamber and 1 year for the parts. This extends to all Rheem Professional Classic Series products. 


09. Rheem Professional Classic Series: RTEX-27

Slightly smaller than the RTEX-36, this ETWH has a temperature range from 80ºF to 140ºF. The copper emission elements are designed with durability in mind and to be easily replaced if necessary.

Like the RTEX-27, the RTEX-36 offers water pressure between 25 and 150 PSI. Additionally, it will turn on at 0.3 GPM – the standard for all Rheem Professional Classic Series.

Sizing

The RTEX-27 is the best tankless water heater for a household of three or fewer people. It has a max temperature increase of 98ºF at a flow rate of 2.0 GPM. At 3 GPM, it has a temperature rise of 62ºF (20ºF less than the RTEX-36).

In addition, the RTEX-27 has a max flow rate of 7.0 GPM. While this is great, the temperature rise for this rate is less than 31ºF. So, for example, if you start with 40ºF water, the resulting temperature would only be 81ºF.

The digital display of the RTEX-27.
The digital display of the RTEX-27.

Dimensions

Height18-1/4 Inches
Width17-5/8 Inches
Depth3-1/2 Inches
Water Connection3/4 NPT
Weight17.8 lbs
Dimensions will help you decide where to install the ETWH.

Specifications

kW27
AMPS113 A
Rec. Breaker Size(3×40)A
Voltage240
Rec. Wire Size (CU)8 AWG
Min. Flow (GPM)0.3
Max Flow (GPM)7.0
Specs for the RTEX-27

Warranty 

The warranty period is 5 years for the heating chamber and 1 year for the parts. This extends to all Rheem Professional Classic Series products. 


10. Atmor 900 Series

The Atmor 900 is one of the best water heaters for your kitchen sink or RV sinks. Its small design allows you to install the ETWH anywhere, keeping itself hidden.

Using only 12kW at peak heating, it’s one of the best electric tankless water heaters for camping.

Sizing

The Atmor 900 has 4 heating settings which are 86ºF, 110 ºF, 120 ºF, and 130 ºF. These settings allow you to control your desired output depending on your climate. So it’s perfect for under-sink ETWH for your RV – being able to set a temperature of 130ºF in cold climates.

Additionally, it has a maximum flow of 1.8 GPM which is suitable for two sinks simultaneously.

The breaker specification for the Atmor 900.
The breaker specification for the Atmor 900.

Dimensions

Height4.09 Inches
Width11.37 Inches
Depth9.25 Inches
Water Connection1/2 NPT
Weight
Dimensions will help you decide where to install the ETWH.

Specifications

kW15
AMPS55 A
Rec. Breaker Size
Voltage220
Rec. Wire Size (CU)
Min. Flow (GPM)0.5
Max Flow (GPM)1.5
Specs for the Atmor 900.

Warranty 

The Atmor 900 has a 1-year warranty period.


11. Atmor Thermo Boost

The Atmor Thermo Boost is a compact ETWH that can provide your whole home with hot water. While it’s suited for warmer climates, you can still use it to supply homes in colder weather.

The Thermo Boost measures the temperature of the inlet and outlet water. Its thermostats then prevent your water from overheating, preventing scorching water.

Sizing

The Thermo boost has a max temperature of 130ºF and a rise of 77ºF. This temperature rise should be able to reach up to 3.0 GPM. However, the Boost can only reach these temperatures at a flow rate of 1.8 GPM.

That’s why it’s recommended to use the Boost as a booster. Connecting the Thermo Boost to your solar heating system will give you your desired water temperatures.

A side profile of the Boost.
A side profile of the Boost.

Dimensions

Height4.09 Inches
Width11.37 Inches
Depth9.25 Inches
Water Connection1/2 NPT
Weight
Dimensions will help you decide where to install the ETWH.

Specifications

kW15
AMPS55 A
Rec. Breaker Size
Voltage220
Rec. Wire Size (CU)
Min. Flow (GPM)0.5
Max Flow (GPM)7.0
Specs for the Thermo Boost.

Warranty

7-year against leaks and a 2-year manufacturer warranty.


12. Eemax EEM24027

The Eemax EEM24027 is one of the best electric tankless water heaters for your whole household. In ideal conditions, it can provide hot water for two showers and two sinks simultaneously.

The unit has an enamel steel panel that covers the copper emersion elements. These elements are threaded and connected to the brass heating elements, making them easy to replace.

Lastly, the unit has a filter for the inlet and operates between 25 and 150 PSI.

Sizing

The EEM24027 has one of the best temperature rises to flow rates on the market. For example, a temperature rise of 63ºF can heat 3.2 gallons per minute. That’s enough water for two water-saving shower heads.

Additionally, the EEM24027 can supply four showers and one sink simultaneously if you live in a warmer climate.

The internal layout of the EEM24027.
The internal layout of the EEM24027.

Dimensions

Height17 Inches
Width17 Inches
Depth3.75 Inches
Water Connection1/2 NPT
Weight13.75 lbs
Dimensions will help you decide where to install the ETWH.

Specifications

kW27
AMPS112.5 A
Rec. Breaker Size(3×40)A
Voltage240
Rec. Wire Size (CU)3×8 AWG
Min. Flow (GPM)0.3
Max Flow (GPM)8.0
Specs for the EEM24027

Warranty

The warranty period is 5 years for leaks and 1 year for the parts.


Final Thoughts

We’ve chosen the 12 best electric tankless water heaters based on their flow rate and temperature rise. We also considered their kWh, knowing that most ETWHs are heavy on electricity when active.

Our five best ETWHs were no exception. For example, our best ETWH for RVs – the EcoSmart POU 6 – only uses 12 kW. That’s roughly 1.9 kW per shower.

We hope this article has shed some light on choosing the right electric tankless water heater for your home. You can join our community to start a conversation or follow us on Twitter.

Dylan Crosbie

Dylan Crosbie

Dylan is a qualified Architectural Technician who's combined his passion for sustainable architecture with journalism. He believes that it's possible for everyone to work towards a sustainable future, even if it’s one small step at a time. This interest has led him to the Climatebiz team where he continues to strive for a greener future for all.

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