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Best Electric Tankless Water Heaters: 2020 Expert Reviews & Recommendations

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Reviews of the Best Electric Tankless Water Heaters

Best Electric Tankless Water Heater
Rheem RTEX 13 Electric Tankless Water Heater
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After testing 11 water heaters, we concluded that the Rheem RTEX-13 Residential Tankless Water Heater is the best electric tankless water heater in the market today. It comes in at an affordable price, sports a mini tank, and has an impressive flow rate of about 6.8 GPM with a temperature rise of 90oF.


The electric tankless water heater is gradually replacing the hot water tank. It has become a widely accepted household appliance in the last five years, thanks to the edge and immense benefits it offers users.

We’ve put together our list electric tankless water heater reviews based on the best-sellers available on the market. In addition, we’ll share maintenance and expert buying tips to guide you in buying the best electric tankless water heater.

If you’d like to see a natural gas water heater, read our tankless water heater reviews.

Best Electric Tankless Water Heater Reviews: Compared

Best Overall
Rheem RTEX-13 Residential Tankless Water Heater
Editor Rating:
5 Star Rating
Flow Rate (GPM):
13 KW
Budget Pick
EcoSmart ECO 27 Electric Tankless Water Heater 27kW
Editor Rating:
4.9 Star Rating
Flow Rate (GPM):
Best Value
Stiebel Eltron Tempra Plus 24 KW Tankless Electric Water Heater
Editor Rating:
4.9 Star Rating
Flow Rate (GPM):
Honorable Mention
Atmor 27 kW/240v Electric Tankless Water Heater
Editor Rating:
4.8 Star Rating
Flow Rate (GPM):
High Power
Stiebel Eltron TEMPRA36B Electric Tankless Water Heater
Editor Rating:
4.8 Star Rating
Flow Rate (GPM):

The Best Electric Tankless Water Heater Reviews: Our Top Picks

Here’s our review of the units we listed in the table above.

Overall Best – Rheem RTEX-13 Residential Tankless Water Heater

Rheem RTEX 13 Electric Tankless Water Heater Review
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The Rheem tankless water heater is the most valuable tankless water heater in our opinion. Rheem designed this unit to deliver on-demand hot water as a single point of use unit.  Additionally, it can serve multilevel faucets within a close range.

Hot water that passes through the unit with ease and is heated by two high-quality copper immersion heating elements. It is equipped with a self-modulating power control feature which allows the unit to regulate its power by itself. This significantly increases the energy efficiency of the unit.

There is an LED display which shows temperature level. The LED screen is adjustable and has an accuracy of +1 degree.

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Features We Love

  • LED display.
  • Self-modulating power control.
  • Less tough installation.
  • Can support other heaters.


  • Installing it isn’t a pain in the neck nor will it dig deep into your pocket.
  • It can work as a point of use heater or support other water heaters.
  • The unit is energy efficient.
  • Installation is simpler, easier, and costs less than some of its competitors.


  • No star energy certification means no green rebates on your energy bill.

Installation cost for the unit is moderate and not over the roof like some models. One owner on a forum indicated the ease of installation. He, however, had prior experience in DIY installations.

For installation, it requires a 3-foot electric cable and 1/2 NPT adapters. These are readily available. Additionally, it’s threaded and this makes the installation less tough.

If you’re looking to get a green rebate with your electricity bill, you’ll be disappointed. The unit has no Star Energy certification even though we came across several comments on different forums that indicate how energy efficient it is.

Budget Pick – EcoSmart ECO 27 Electric Tankless Water Heater

EcoSmart Eco 27 Electric Tankless Water Heater Review
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The EcoSmart ECO27 electric tankless water heater is one smart water heater. It’s available in different variants with several features to differentiate. The other members of the ECO family from EcoSmart include the ECO 8, ECO 18, ECO 24, ECO 11, and the ECO 36.

We like the fact that the ECO 27 tankless electric water heater comes with the self-modulating technology seen on the Rheem tankless water heater. With the self-modulating technology, energy costs have no choice but to drop significantly.

The unit is adequately sized, measuring about 17H x 17W x 3.625D inches. It’s available in white color and comes with an LED screen. Just below the LED screen, you’ll find the control knobs for the unit. The control button is responsive and is coated with silver material thus giving it a shiny resplendent look.

View Features and Pros/Cons

Features We Love

  • Self-modulating technology.
  • Compact sized.
  • Sleek design with LED screen
  • Responsive temperature control knob.


  • As we already know, the self-modulating technology can save a lot of energy. This directly reduces energy costs significantly.
  • It’s compact size and sleek design makes it easy for the unit to fit into most spaces.
  • It comes with a responsive control knob coated in silver.
  • LCD display provides crystal clear information about the temperature.


  • The heating elements inside the unit are made of copper. Therefore, they are susceptible to corrosion.

With regards to power, the unit requires 27kW at 240V. It requires three 40 amps double pole breakers and a 200 amps electrical panel. The flow rate is impressive, although the activation flow rate of 0.3 GPM isn’t. However, it won’t hinder you from getting your hot water.

Installation costs don’t come cheap although they’re not outright expensive. For the pipe connections, it requires the 3/4 inch NPT connection. EcoSmart suggests professional installation for those who aren’t conversant with DIY installations.

Some of the internal components of the unit are made with copper and stainless steel to ensure that they last longer and are easy to replace when it’s time for a replacement. If you’re interested in something smaller yet powerful, the EcoSmart ECO 11 Electric Tankless Water Heater is the younger sibling of the ECO 27 and will still meet your hot water needs.

Best Value – Stiebel Eltron Tempra Plus 24kW Tankless Electric Water Heater

Stiebel Eltron 24 Plus Electric Tankless Water Heater Review
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What is it about the Stiebel Eltron heater that made us include it in this list even though it’s quite pricey?

The Tempra Plus 24 kW heater rocks a classic look as it’s clad in white. It features an LED screen which displays the current temperature. Just below the LED screen, you’ll find the soft touch control buttons as well as a control knob for easy temperature adjustment.

This Tempra 24 Plus unit is a member of the Tempra Plus Series family, most of which have been discontinued. It measures 4.62 x 16.62 x 14.5 inches – pretty compact size for such capabilities.

Steibel designed this unit to be energy efficient although it doesn’t come with the self-modulating technology we’ve seen in some units on this list. You’ll most likely see a 15% decrease in energy bills and perhaps, an increase in water bill because more of your family members especially your kids, will spend a long time in the shower, thanks to the endless hot water from the unit.

View Features and Pros/Cons

Features We Love

  • Space saving design.
  • Easy to use temperature controls.
  • Activation flow rate of 0.5 GPM.
  • Can be installed to support other water heaters.


  • The unit is priced fairly.
  • It has an activation flow rate of 0.5 GPM.
  • Compact sized.
  • It supports existing heaters.


  • None.

Power requirement is pegged at 240V with a wattage of 24kW. Additionally, the unit has an activation flow rate of 0.5GPM, a tad above the EcoSmart ECO 11 water heater we reviewed earlier.

For installation purposes, the unit requires a 2 – 50 amp breaker. The cost of installation is slightly above average. This can be caused by a change in electrical connections in the home to support the unit. Steibel strongly advises that a professional handle the installation of the unit.

In the absence of the self-modulating technology, the unit in lieu has the Advanced Flow Control Technology. The Advanced Flow Control technology works by slightly reducing the flow of water automatically when many faucets are drawing hot water simultaneously.

It enables the unit to keep producing hot water without running out. In the absence of the Advanced Flow Control technology, the unit may not be able to keep heating water, hence some faucets will be getting cold water instead.

#4. Atmor Electric Tankless Water Heater

Atmor Electric Tankless Water Heater Review
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Sitting princely on the number four spot of our whole house water filter is the Atmor Electric tankless water heater. This unit boasts of a 5.1GPM although the flow rate is dependent on the temperature increase.

Atmor offers this electric tankless water heater in various configurations such as 11kW, 14kW, 18kW, 24 kW, and the 27kW which we’re reviewing. All the aforementioned variants need 240V of power to run effectively.

In addition to that, the Atmor electrical tankless water heater requires three 40 amp DP breakers as well as three 8AWG wires.

View Features and Pros/Cons

Features We Love

  • Responsive control knob with a digital screen.
  • Heats up water in a matter of seconds.
  • An average flow rate of between 2.63 and 5.4 GPM.
  • It’s compact sized.


  • This unit is compact in size thus finding an installation space won’t be a problem.
  • It comes with a display screen which is controlled by a knob.
  • Atmor offers this heater in a variety of options to suit your needs and your budget.
  • It is energy efficient.


  • You’ll need some copper wiring for installation and it has to be purchased thus increasing installation costs.

The Atmor electric tankless water heater is a combination of two affordability and efficiency. It costs a tad less than the Rheem RTEX 13, our top pick, but that’s not all – the unit sports digital controls.

There’s a display screen which keeps you informed about the unit’s temperature at any given time. Slightly below the display screen is the chrome coated control knob which is smooth and responsive.

Installing the unit can be quite tough for a newbie. Hence, Atmor advocates for professional installation for the unit. However, they provide clear installation instruction for the unit to guide you during the installation process.

In terms of energy efficiency, the Atmor does pretty well. You’ll definitely notice a slight drop in your energy bill. As we mentioned earlier, the Atmor electric tankless water heater has a flow rate that fluctuates between 2.63 GPM and 5.4 GPM depending on the temperature rise.

#5. Stiebel Eltron TEMPRA36B Electric Tankless Water Heater

Stiebel Eltron Tempra Electric Tankless Water Heater Review
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The Stiebel Eltron Tempra electric tankless water heater is closely related to the Tempra Plus we reviewed above. It, however, shares only a few similarities with it. The chief reason why we included this unit in this review is that it’s energy efficient.

In all honesty, one seldom comes across an appliance that can significantly reduce energy bills by more than 40%. The unit is equipped with a power control system designed to maximize energy usage when it’s on. On the other hand, the unit doesn’t use any energy when it’s in the rest mode.

Aside from being energy efficient, it also boasts of an impressive flow rate which flutters between 1.5GPM and 3GPM depending on the temperature rise. In addition to that, the unit has a wattage of

View Features and Pros/Cons

Features We Love

  • Energy efficient.
  • Good flow rate between 1.5 to 3GPM.
  • Power management system.
  • Compact sized.


  • This heater is highly energy efficient.
  • It can deliver water at flow rates between 1.5 3 GPM although this is subject to temperature rise and the number of faucets that need hot water simultaneously in your home.
  • It’s compact-sized and this allows for installation even in small spaces. Be sure to install it in a place where it can be accessed easily for future repairs.


  • It’s pricey.

Furthermore, the unit is capable of heating water irrespective of the type of water it is – hard or soft. We, however, encourage you to install a whole house water filter or a water softener in your home as it will help protect appliances such as these from being clogged and damaged by minerals in the water.

The only obstacle that will hinder you from owning this electric tankless water heater is the price. It’s quite pricey, and installation costs take the price up slightly.

Electric Tankless Water Heater Comparison Table

NameOur RatingFlow RatekWPrice
Rheem RTEX-1354.0 GPM13 kW$$
EcoSmart ECO274.92.5 GPM27 kW$$$
Stiebel Eltron Tempra Plus4.93.0 GPM25 kW$$$$
Atmor 27kW/240v4.82.6 GPM27 kW$$
Stiebel Eltron Tempra 36B4.83.0 GPM36 kW$$$$

How Does An Electric Tankless Water Heater Work?

Most electric tankless heaters heat water on-demand (as opposed to storing hot water in a tank), which results in energy and cost savings.

There are mini tank models classified as tankless water heaters. These mini-tank water heaters have small tanks that hold a limited amount of hot water. It’s akin to a water dispenser although both aren’t the same.

Tankless water heaters are powered by either an electric or gas elements. In this review, we’re only concerned with the electric models.

Let’s answer a few questions about using an electric tankless water heater.

What are the advantages of using a tankless water heater?

It’s important that we talk about the benefits of using a tankless water heater. Are tankless water heaters worth it? Why are they better than their tank model? We shared the advantages of using them in the lines below.

Saves Space

With a tankless water heater, you have nothing to worry about in terms of space. Tankless water heaters have no tanks, so the issue of finding where the tank will fit won’t arise.

Again, most tankless water heaters are designed to be wall mounted. This saves valuable floor space especially when it’s being installed in a room with limited space.

Saves Costs

This is one of the most important perks of using a tankless water heater. When using the traditional tank models, you fill the tank with water to a certain level before turning on the unit.

If for any reason, you’re unable to completely use the water you heated, then the leftover is now a waste. Someone else who wants to use hot water will have to heat the water again.

This significantly increases the energy bill in the long run. On the other hand, the tankless model heats up the water as you open the faucet. It turns off as soon as you turn off the faucet.

Clean Water

With a tankless water heater, you don’t have to deal with water that has been contaminated in the tank by rust and other sediments. Using a tankless water heater thus ensures you have clean hot water at your disposal at all times.

Lasts Longer

The traditional tank water heaters are known to last for up to a decade or two. A tankless water heater will last longer than that especially when you follow the manufacturer’s instructions.

More Hot Water

With a tankless water heater, you have more hot water to use at home. This eliminates the scheduling of bathing times in the house and no one has to use cold water to bath.

Saves Time

This is another great advantage of installing a tankless water heater. It saves you a lot of time. You won’t have to wait for the tank to refill as in the case of the tank models.

Any drawbacks? Well, the only drawback of tankless water heaters is the cost of installation.

Best Electric Tankless Water Heater Buying Guide

If you’ve decided to buy an electric tankless water heater, congratulations. However, you’re not yet certified fit to buy the unit until you’ve read and digested the contents of this buying guide.

How Many Devices Needs Hot Water Simultaneously In Your Home?

First, you should consider the number of devices and faucets that need hot water in the house. Check the total number of faucets in each room, especially for rooms that are ensuite.

Next, take note of the flow rate of these faucets and devices. Note which ones will run simultaneously. For instance, the faucets in the master bedroom and the one in the kitchen and that of the children’s room might run simultaneously.

Add the sum of their flow rates together. This gives you an idea of the flow rate the unit you purchase must have.

Here’s an estimate of the water flow rates of some of the common devices and faucets.

  • Faucets: They typically have a flow rate of about 0.75 GPM to 2.5 GPM.
  • Shower heads: These have a flow rate of about 1.2 GPM to 3.5 GPM.
  • Washing machines and dishwashers: They have a flow rate of 1 GPM to 2 GPM.

These are general assumptions. A good way of finding out the exact flow rate of your faucet or appliance is to check the product’s manual or to check online using the model number of the product.

What’s The Temperature Of your Incoming Hot Water?

This is the second thing you must take note of. Plumbing Supply provided a list of possible temperatures for groundwater here in the US. Your district’s water authority can also furnish you with this information if you request it.

Knowing the temperature of the incoming water, we can proceed to the next stage.

Calculate the Temperature Rise

The temperature rise refers to the amount of heat temperature that the water heater will need to heat the water that passes through it. You don’t need to be a mathematician to do this.

To calculate the temperature rise, just deduct the incoming water temperature you obtained above from the temperature you desire. For instance, if your incoming temperature is 48oF, and you desire water that is 110oF hot, simply subtract 48 from 110. Your answer will be 62oF.

Armed with this precious information i.e. the flow rate of your appliances and the temperature rise, you’re well equipped to find a unit that suits your household.

Find an electrician and a plumber

Since you’ll be using an electric tankless water heater, an electrician will help install the unit. The duty of the electrician is to create new wiring and install breakers required by the unit.

The plumber has to do the minor plumbing works. It’s not uncommon to find professionals who can handle both the electrical and plumbing installations. However, this can be very expensive. But it’s worth it.

Installation location

Select a suitable space in the home where the unit will be installed. Ensure that the unit is not installed in a place where children will have access to it. Some of the tankless water heaters can be mounted on a wall. If you have the space on the wall for it, you should opt for such a model.

If you don’t have space inside the house to install the unit, opt for a unit that can be installed outside the house.

A Good Flow Rate

Now that you’ve taken note of the flow rate of the faucets and appliances in your home earlier, you should buy a unit that exceeds that flow rate. At least 6 GPM to 8 GPM is acceptable for most homes.

Which Size Do You Want?

Take a look at this video?

This clearly indicates that tankless electric water heaters come in various sizes and shapes. Each size is suitable for a specific number of faucets. If you have a large household, then you should opt for the larger models and vice versa.

Do You Want A Mini Tank Model?

Mini tank water heaters are often classified as tankless water heaters because of their size. They often appear to have no tanks but in reality, they have small tanks which hold only a small amount of hot water.

The hot water held in this tank is released immediately you turn on your faucet. It makes up for the lag time on some units which may need a few seconds to get the required hot water to you.

How To Take Care Of Your Tankless Electric Water Heater

Given the nature of the water that flows into tankless water heaters, it’s important we do our best to keep the unit in proper working condition. In this section of the article, we’d like to show you some of the things you need to do to elongate the lifespan of your tankless water heater.

  1. Don’t turn on your tankless electric water heater when the electric current is low.
  2. Install a water softener especially if your water is hard water. The water softener will remove the hardness impurities from the water thereby reducing the time it takes for it to boil.
  3. Don’t allow water to touch the electrical parts of the unit. Install it in a clean dry place.
  4. Flush your unit at least once in 9 or 12 months.
  5. Check the water pipes leading to the unit for signs of corrosion and leaks. Make the necessary repairs.
  6. If your unit makes any noise which seems to be getting progressively louder, please contact a professional to have a look inside to know what the problem is. Replace the part that is responsible for making such noise.

The video below shares more maintenance tips…

How To Flush Your Tankless Electric Water Heater

Flushing a tankless electric water heater is an important thing to do if you want the unit to function efficiently.

The video below should serve as a guide on how to flush your electric tankless water heater.

Final Words…

Getting an electric tankless water heater will significantly reduce the amount of energy you use for heating water in your homes. Proper maintenance, on the other hand, will ensure that your unit will live as long as Methuselah, literally.

We hope you enjoyed reading the review. What are your thoughts? Share with us below.

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