Best Electric Tankless Water Heater for Your Home

Tankless Electric Water Heater Reviews

Imagine having the ability to install your water heater nearly anywhere in your home without having to worry about space, ventilation, or even the threat of gas leaks. Those are just a few of the benefits you’ll enjoy when you find the best electric tankless water heater for your property.

Replacing your existing water heater with a new and improved unit is something that many homeowners and commercial property owners should consider. There’s nothing more comforting than knowing you’ll have an endless stream of hot water, without having a large utility bill at the end of the month. 

Bosch Electric Tankless Water Heater - Eliminate Time for Hot Water - Easy Installation
Stiebel Eltron 24 Plus Tempra, Tankless Water Heater, White
Best Value
EcoSmart ECO 27 Electric Tankless Water Heater, 27 KW at 240 Volts, 112.5 Amps with Patented Self Modulating Technology
Rheem RTEX-27 240V 3 Heating Chambers Residential Tankless Water Heater
Bosch Tronic 6000C
Stiebel Eltron Tempra Plus 24
EcoSmart ECO 27
Rheem RTEX-27
27 Kw
24 Kw
27 Kw
27 Kw
.80 GPM Minimum Activation
.50 GPM Minimum Activation
.30 GPM Minimum Activation
.30 GPM Minimum Activation
97% Efficiency
99% Efficiency
99.8% Efficiency
99.8% Efficiency
Warranty: 5-yrs Heating Chambers / 2-yr parts
Warranty: 7-yr leakage / 3-yr parts
Limited Lifetime Warranty
Warranty: 5-yrs Heating Chambers / 1-yr parts
Maximum Temp: 131F
Maximum Temp: 140F
Maximum Temp: 140F
Maximum Temp: 140F
12-1/2 x 15-3/4 x 4-1/2
17-1/2 x 16-5/8 x 4-5/8
17 x 17 x 3-3/4
18-1/4 x 17-3/4 x 3-3/4
$591.54
$697.97
$451.57
$639.21
Bosch Electric Tankless Water Heater - Eliminate Time for Hot Water - Easy Installation
Bosch Tronic 6000C
27 Kw
.80 GPM Minimum Activation
97% Efficiency
Warranty: 5-yrs Heating Chambers / 2-yr parts
Maximum Temp: 131F
12-1/2 x 15-3/4 x 4-1/2
$591.54
Stiebel Eltron 24 Plus Tempra, Tankless Water Heater, White
Stiebel Eltron Tempra Plus 24
24 Kw
.50 GPM Minimum Activation
99% Efficiency
Warranty: 7-yr leakage / 3-yr parts
Maximum Temp: 140F
17-1/2 x 16-5/8 x 4-5/8
$697.97
Best Value
EcoSmart ECO 27 Electric Tankless Water Heater, 27 KW at 240 Volts, 112.5 Amps with Patented Self Modulating Technology
EcoSmart ECO 27
27 Kw
.30 GPM Minimum Activation
99.8% Efficiency
Limited Lifetime Warranty
Maximum Temp: 140F
17 x 17 x 3-3/4
$451.57
Rheem RTEX-27 240V 3 Heating Chambers Residential Tankless Water Heater
Rheem RTEX-27
27 Kw
.30 GPM Minimum Activation
99.8% Efficiency
Warranty: 5-yrs Heating Chambers / 1-yr parts
Maximum Temp: 140F
18-1/4 x 17-3/4 x 3-3/4
$639.21
  • You should always seek the help of a professional for installation as the majority of electric water heaters will need their own dedicated breaker to protect the other circuits in your home.

How to Choose the Best Electric Tankless Water Heater

How Does an Electric Tankless Water Heater Heat Water?

The incoming cold water is heated as it passes thru several electric heating elements. When a hot water faucet in your kitchen is opened, cold water begins to flow into the tankless heater. 

The second the unit detects the incoming water, the electric heating elements fire-up to heat the cool water. Once the incoming water stops, the heating elements shut-down and the tankless has completed it's task. 

Tankless heaters are often called on-demand water heaters because they only operate when there's a demand for hot water. Electric tankless water heaters operate entirely differently than a gas tankless unit, and in addition, they are far more energy efficient and easier to maintain.

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What's the Difference Between a Tankless and Conventional Water Heater?

Without the need for a tank, the difference between a tankless and a tank-style water heater may seem obvious. But there is far more that separate them than the lack of a tank. Let's take a look at a few of the major differences:

Endless Stream of Hot Water - When sized correctly, you'll never run out of hot water with a tankless heater. A conventional water heater is limited by the tank size, and once drawn down the unit will need time to heat more hot water.

Space Savings - Since a tankless water heater is mounted on the wall, their compact design requires far less space than a conventional heater. 

Energy Savings - Conventional tank-style water heaters are always operating. They are either heating water or keeping the water within the tank hot, which is called Standby Heat Loss

A tankless unit runs much more energy efficienctly because it only turns on when there's a demand for hot water. Since water isn't sitting in a tank, you'll always know that your hot water is fresh and clean.

Costs - Although the initial purchase and installation costs may be higher for a tankless water heater, it's easily offset by the monthly utility savings over the next couple of years due in part to the lack of Standby Heat Loss. 

Replaceable Parts - A conventional tank-style water heater has a service life expectancy of 8 to 12 years. If the internal tank begins to leak, your only option is to purchase a new water heater. 

A tankless unit is designed to last up to 20 years and the majority of the internal parts can be serviced or replaced. 

Peace of Mind - When a conventional water heater's tank fails, you're looking at 30-80 gallons of rusty, hot water on your floor! Considering 7 out of 10 tanks either burst or leak, the odds aren't in your favor.

Best Electric Tankless Water Heater Reviews

How to Buy an Electric Tankless Water Heater

Buying a tankless water heater is a big decision and it's critical that you take the time to find a unit that can deliver enough hot water for your home. Just browse thru some of the tankless reviews and you'll find plenty of individuals who are disappointed that their unit wasn't able to keep up with the hot water demand.

With a little research and an understanding of how electric tankless water heaters operate and how to find the right one for your needs, you should definitely find yourself on the "satisfied customer" list. We recommend reading a couple of our articles; Tankless Water Heater Buyers Guide and Gas vs Electric to help you get started.

  • Buying a tankless water heater does not mean you'll have instanteous hot water. The water will still need to travel from the heater, thru the pipes, to the faucet or shower head. The farther the faucet is from the water heater, the longer you'll need to wait for hot water . . . just like with a tank-style water heater. Consider purchasing a point-of-use water heater at the source (such as in a bathroom) for instanteous hot water.
This video will give you a good overview of how to select a tankless water heater. 

Tankless Water Heater Buyers Guide

Selecting the correct sized tankless water heater is critical. If you purchase a unit that's too small for your needs, you'll be disappointed and frequently find yourself using cold or lukewarm water. If you purchase a unit that is too large, you're spending unnecessary money and may have completed unneeded electrical upgrades to your home. 

Selecting the Right Sized Unit

Determining which tankless is the right size for your home is called sizing. To properly size your tankless, you'll need to determine the necessary flow rate needed to adequately service your home.

You'll also need to know the incoming water temperature so you can determine the temperature rise (or how hard the unit will need to work) to ensure that the tankless will be able to deliver the necessary flow rate.

Don't worry, it's actually not as hard as it sounds.

All tankless manufacturers provide sizing charts, which is simply a way to communicate how much hot water, measured in gallons per minute (GPM) the heater can deliver under ideal conditions. Once you know your required flow rate and the necessary temperature rise, you can match these numbers to the manufacturer's sizing chart to find the model that best meets your needs.

How to Determine Your Flow Rate

Flow rate is measured in gallons per minute (GPM), and it's the amount of water the tankless is able to heat at any given time. As an example, if a tankless has a flow rate of 3.5 GPM, you can expect the unit to deliver 3.5 gallons of hot water every minute.

To determine your household's required flow rate you'll need to know how many hot water fixtures are used at the same time during peak usage. Add each water fixture's GPM to calculate the total GPM needed.

As an example, if your household takes 2 showers at the same time, and each shower head uses 2.2 GPM, your peak hot water need is 4.4 GPM (2.2 +2.2 = 4.4). Read our extensive article on How to Buy a Tankless Water heater for more details.

How to Determine Your Temperature Rise

Temperature Rise is the difference between the heated output temperature and the incoming ground water temperature. If the incoming water temperature is 52F and your desired hot water temperature is 100F, the temperature rise will be 48F (100 - 52 = 48).

The GPM the unit can deliver is affected by the incoming water temperature. As an example, the incoming water temperature in Florida (67F) is much warmer than that of Nevada (47F). This means, that the same exact tankless water heater won't be able to deliver the same GPM in both locations. The heater in Nevada will need to work much harder to heat the water (temperature rise), and therefore will deliver a lower GPM.

This video explains how to properly size a water heater:

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Best Electric Tankless Water Heater: Top Picks

There are plenty of models on the market today, and each has a different design and a variety of options. Selecting the right tankless for your household can seem like a daunting task. That's why we've curated a list of the top four electric tankless water heater models that we think have a lot to offer.

Most of these models can be purchased in larger or smaller sizes to allow you to find the exact fit for your home's hot water needs.

As one of the top-tier brands when it comes to home appliances, Bosch has a convenient solution to heating water without needing a lot of space. With the help of the Bosch Electric Tankless Water Heater, you'll be able to give your whole house stable, temperature-controlled water without having to rely on gas.

This device comes with a simple, user-friendly interface and it's designed to replace a 40-gallon electric tank-style water heater. According to Bosch's Sizing Chart, the WH27 model should be able to achieve a 3.5 GPM with a temperature rise of 45F.

Key Features

  • Built to last with 2 solid copper heat exchangers and brass fittings.
  • The thermal cut-out switch is not only an excellent safety feature, but it'll also protect the heating elements from the damages caused by dry-firing. 
  • The sleek and compact design not only looks good, but it also can fit nearly anywhere. 
  • The built-in flow sensor and polymer encased elements ensures a constant  output temperature.

Pro's

  • Temperature range: 95 and 131F
  • Sleek, modern, compact design
  • Direct replacement for Bosch Tronic 5000c WH27
  • Ideal size for installing in tight spaces

Con's

  • A higher activation flow (.8 GPM) than most units.
  • Size and fittings slightly different from other Bosch older models
  • The Bosch Tronic 6000C  WH27 was designed to directly replace the Bosch Tronic 5000C WH27. In addition, it will also replace 2 older models in Bosch's line-up: The Bosch PowerStar AE125 and the Powerstream Pro RP27PT. The size and fittings are slightly different for the 2 older models, so some modifications may be necessary.

Bottom Line

The Bosch Tronic 6000C WH27 falls into the mid-price range for electric tankless water heaters. It's definitely a nice pick if you don't want to splurge for the higher-end units.

Bosch is a reputable company and there's a lot to like about this unit beyond it's sleek good looks and solid workmanship. According to their website, you can expect to see 3.5 GPM at a 45 degree temperature rise. This is a respectable performance for an electric tankless water heater and should be able to service 1 to 3 major appliances. 


The Stiebel Eltron Tempra Plus is a heavy-hitting tankless water heater that you can use for both residential and commercial properties.

There's little doubt that Stiebel Eltron makes outstanding tankless water heaters. With German engineering and hands-on experience since 1924, you can rest easy that you're buying the best of the best. 

The grey Tempra and Tempra Plus series is undergoing a cosmetic refresh. The "old" gray and "new" white models have the same dimensions, requirements and interiors. However, the "new" white models come with a shiny new housing, and an improved display and thermostat interface which includes:

  • Preset temperature memory buttons
  • Energy monitor showing cost savings
  • Flow rate meter

Beyond the cosmetic changes and display and thermostat improvements, they're basically the same unit. According to Stiebel Eltron's Sizing Chart, the Tempra Plus should be able to achieve 3.1 GPM when the incoming water is 52F.

Key Features

  • The digital display on the unit shows the desired set temperature, and the bar below displays the power capacity status. This bar has 10 segments, each representing 10%. When the unit is operating and 5 bars are displayed, the Tempra Plus is operating at 50% capacity!
  • Although the Tempra Plus has a temperature range between 68 and 140 degrees Fahrenheit, you'll have the ability to limit the maximum temperature to 109F to prevent scalding. This can be especially helpful if you have small children.
  • The Tempra Plus uses Self-Modulation Energy technology to ensure the unit uses the least amount of energy possible when heating the water. Sensors are used to monitor the temperature of the incoming and outgoing water, and measure the flow rate as the water passes thru the heater. The micorprocessor processes the data and adjusts the heating elements as needed to deliver hot water efficiently using the least amount of energy possible.
  • The Advanced Flow Control feature is one of the key things that makes the Tempra Plus such a quality product. Simply set the output temperature and the Tempra's microprocessor delivers a steady temperature output by adjusting the flow.

Stiebel Eltron explains their Advanced Flow Control feature like this: "If the demand asked of a Tempra® Plus is greater than the unit can handle, Advanced Flow Control works by slightly reducing the flow of water. Instead of delivering colder water than the set point, a Tempra® Plus automatically delivers slightly less water, but at the correct temperature."

Pro's

  • Quality workmanship. Made in Germany
  • Advanced Flow Control allows the unit to keep a constant output temperature during high demand periods
  • Without mechanical switches, the unit is virtually silent 

Con's

  • Higher priced than most other electric water heaters
  • Slightly lower GPM than other units

Bottom Line

It's hard to find many short comings on the Tempra Plus 24. Once installed, it'll operate quiet as a ghost delivering hot water at a consistent temperature.

The award winning Advance Flow Control feature is unique to Stiebel Eltron, and it enables their units to deliver hot water by adjusting the flow.

Like all tankless water heaters, it'll need regular maintenance to keep it running in peak condition, but with the proper care, the Tempra could easily last over 20 years!

According to their literature, you can expect 3.1 GPM if the ground water temperature is 52 degrees. This should be able to service 2 showers at the same time. This is slightly lower than the other units on our list, but the Advanced Flow Control helps this tankless operate extremely efficiently, and the quality workmanship and engineering will keep it running for decades!


The ECO 27 is one of the largest tankless water heaters manufacturered by EcoSmart, however, if you need more hot water, you should take a look at the more powerful ECO 36. But don't be fooled, the ECO 27 is capable of delivering hot water to a single family home . . . even in colder climates!

EcoSmart designs their water heaters to be sold at a price point that can meet most budgets, and this is a well-made, very popular unit, with plenty of 5-star reviews to back up it's appeal.

According to EcoSmart's Sizing Chart, the ECO 27 is capable of delivering 3.48 GPM of hot water when the incoming water temperature is 52F.

Key Features

  • The self-modulating technology allows the unit to adjust the amount of energy used to the amount of hot water needed. This feature helps the ECO 27 meet your hot water needs in the most energy efficient way possible. 
  • The energy efficiency of the ECO 27 is impressive. It can achieve 99.8% efficiency! 
  • Equipped with thermal auto protection, you can rest assured that your water heater won't overload or overheat.
  • The digital interface is intuitive and capable of delivering 1-degree temperature adjustments.

Pro's

  • Temperature can be adjusted in 1 degree increments
  • Temperature range: 80 and 140F
  • Copper and stainless components

Con's

  • Unit must be professionally installed within 30 days of purchase to be eligible for the limited lifetime warranty
  • Not as visually appealing as other units

Bottom Line

The EcoSmart ECO 27 has become a popular electric tankless water heater choice. The manufacturer delivers a quality product at a reasonable price. It doesn't have the stunning good looks as the Stiebel Eltron or Bosch units, but it's a hard worker and well liked among home owners.

We love that it has a Limited Lifetime Warranty, however, read it carefully, there are a number of fine print items.

EcoSmart states that this unit should be able to achieve a 3.48 GPM if the incoming water temperature is 52 degrees. This flow rate should be able to easily service 2 shower heads. Making this a powerful water heater for the price.


Rheem is a leader in the industry, and the RTEX-27 doesn't disappoint.  With the user-friendly design and minimalistic appearance, this whole house electric tankless water heater delivers a powerful stream of hot water while maintaining an impressive energy efficiency of 99.8%.

Designed to provide years of service, there are plenty of internal features, which makes this one of the most comprehensive, self-modulating units on the market.

Rheem offers a handy sizing tool to help you find the right unit for your geographic area and household needs. But a quick look at their Sizing Chart shows that you can expect this unit to deliver 4.0 GPM at a 46F temperature rise, making this one of the most powerful electric tankless water heaters around!

Key Features

  • At peak performance, the Rheem RTEX-27 can deliver 6.6 GPM! Enough hot water to service 4 showers and 1 faucet. 
  • Electronic temperature control with easy to read display. The temperature can be adjusted in 1 degree increments.
  • Advanced self-modulation allows the unit to meet the hot water demand by adjusting the amount of energy used.
  • 3 Durable Copper Immersion heating elements with brass tops heat the water. They're not only long lasting, but also field serviceable when replacement is necessary.
  • The RTEX-27 can be wired for 208v instead of 240v. However, there is a 25% performance downgrade.

Pro's

  • 3 Copper Immersion heating elements that can be serviced in the field
  • Extremely powerful and in optimal conditions can have a max GPM of 6.6.
  • Temperature range: 80 to 140F

Con's

  • On the higher side of the price range
  • Professional installation is recommended (but that's true with all tankless water heaters)
Bottom Line

The Rheem RTEX-27 tankless is a high quality electric tankless water heater. There's a lot to like about this unit, including it's commanding good looks, powerful water heating, and expert engineering.

Purchasing a tankless unit of this quality, from a reputable company is generally going to be on the higher side of the price range, and that's ture with this unit. But there's peace of mind in knowing that Rheem is frequently the "go-to" brand that plumbers recommend. 

With the proper care, this unit should last many years. If you're  looking for an electric tankless to stand the test of time, the Rheem RTEX-27 should definitely be on your short list.

Rheem states that the RTEX-27 has a maximum GPM of 6.6, but keep in mind that most areas won't be able to reach those numbers. However, this is an extremely powerful unit and at a 46F temperature rise, the heater should be able to achieve a 4.0 GPM.


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Final Thoughts

All of the electric tankless water heaters on this list are quality products from reputable manufacturers. Which one you select depends largely on your household hot water needs and budget.

If money isn't an issue, you may want to consider the Rheem RTEX-27 or Stiebel Eltron Tempra Plus. Both are impressive and among the best on the market. The Rheem RTEX-27 packs a lot of water heating power into it's sleek looking unit, and we particularly like the Advanced Temperature Control features the Stiebel Eltron offers.

If you're looking for a stylish unit to fit into small spaces, the Bosch Tronic 6000C WH27 gets our vote. Less expensive than some, this unit will not only get the job done, but you can tuck it away into the smallest of corners. 

The ECO 27 stands up well to the higher priced units, and the manufacturer backs it up with a limited lifetime warranty. Not to mention, the unit is easy to use and well liked among homeowners. This tankless definitely gets our vote for best bang for the dollar!

Whichever tankless water heater you choose, we recommend installing a sediment filter on the incoming water line to protect the unit, and flushing it regularly to keep it running in optimal condition. With the proper care, your new tankless should last over 20 years!

Last update on 2018-11-21 / Affiliate links / Images from Amazon Product Advertising API