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5 Best Electric Tankless Water Heater Reviews & Ratings

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In many ways electric tankless water heaters are under appreciated in the world of on-demand hot water. They offer many advantages over their gas fuelled cousin, but frequently don't receive the credit they deserve.

Although, they do have short comings, their versatility and superb energy efficiency make them hard to ignore. Read on to find out how to purchase the best electric tankless water heater for your home.
Still on the fence about electric and gas? Then see our guide of the best tankless water heaters on the market today.

"Our Pick" for Best Electric Tankless Water Heater

Here are our top 5 picks for the best electric tankless water heaters on the market today:

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Top Pick: Stiebel Eltron Tempra 36 Plus

Stiebel Eltron 36 Plus Tempra, Tankless Water Heater, White

With its sleek good looks and superior German engineering this model is designed for performance. The company offers a solid warranty that covers 7-years against leakage and 3-years against defects in workmanship and materials, so you can trust that they stand behind their product.

Stiebel Eltron's exclusive Advanced Flow Control means the hot water will always maintain your desired temperature even if the demand exceeds the system's capacity.

Intelligent self-modulating technology, with solid copper heating chambers, ensures that the Tempra Plus is always using the least amount of energy possible.

The Tempra 36 Plus is Stiebel Eltron's largest electric tankless water heater. It's capable of servicing 3 to 4 bathrooms in warm climates, or 2 to 3 bathrooms in cooler climates. But if you don't need quite as much hot water, they have several smaller systems available.

  • Great Warranty: 7-years against leakage and 3-years against defects in workmanship and materials
  • Advanced Flow Control means the hot water will always maintain your desired temperature
  • Intelligent Self-Modulating technology means the unit is always using the least amount of energy possible.
  • Built to cope in household that have a high demand for hot water (up to 4 bathrooms).

Rheem RTEX-36

Rheem 240V 4 Heating Chambers RTEX-36 Residential Tankless Water Heater

Rheem is a global leader when it comes to water heaters. The company has been in business a long time and over the years they've built a reputation as a high-end player. They manufacture tankless systems that can deliver large amounts of hot water, and they back their units with a solid 5-year heat exchanger / 1-year parts limited warranty.

The RTEX 36 is the largest tankless system in Rheem's RTEX line-up. It has four durable copper immersion heating elements with brass tops. Should you ever need to replace one, they're threaded for easy field removal and replacement.

This workhorse is capable of delivering up to 8.8 gallons of hot water per minute, it can handle as many as 5 showers and 2 faucets depending upon your geographic location.

  • Solid 5-year heat exchanger / 1-year parts limited warranty.
  • Up to 8.8 gallons of hot water per minute.
  • Built to handle as many as 5 showers and 2 faucets.

EcoSmart ECO36

Ecosmart ECO 36 36kw 240V Electric Tankless Water Heater

The ECO 36 is the largest tankless water heater in EcoSmart's ECO line-up. Priced competitively, EcoSmart has built a reputation as being a customer favorite.

By far, EcoSmart offers the strongest warranty of the four tankless systems on our list. The limited lifetime warranty applies to exchangers, electronics and heating elements, but if you live outside of the United States or Canada, the warranty drops to a respectable 5-years. Be sure to read the fine print as there are a few things that must take place for the warranty to be valid.

With self-modulating technology, the ECO 36 adjusts its energy usage based on the demand for hot water. Thus helping the system achieve a stunning 99.8% energy efficiency! And the durable copper and  stainless steel components are designed to be easily removed, should they ever need to be replaced.

The EcoSmart ECO 36 is manufactured to meet the hot water demands for a large household. At it's peak performance, the system can deliver enough hot water for two sinks and four showers simultaneously.

  • By far, EcoSmart offers the strongest warranty of the four tankless systems on our list.
  • 99.8% Energy Efficiency.
  • Delivers enough hot water for two sinks and four showers.

BOSCH Tronic 6000 WH27

Bosch Electric Tankless Water Heater - Eliminate Time for Hot Water - Easy Installation

The Bosch Tronic 6000 is one of two lower capacity electric tankless water heaters on our list, but that doesn't mean its short on performance. Bosch manufactures two units in the Tronic 6000 line-up. The WH 17, which has a kilowatt rating of 17.3, and the WH 27, with a kilowatt rating of 26.9.

The WH 27 is the perfect tankless to replace a 40-gallon electric tank-style water heater to help you lower your energy bills. With solid copper heat exchangers, this unit was built to last, and the company stands behind their product with a 5-year heating module limited warranty.

Designed as a whole house tankless, the WH 27 can easily be used to give a boost to your primary heating system. Simply position it close to a bathroom or other source, and it'll kick in immediately to fill the gap until your main hot water heating system is ready to take over.  

  • The WH27 is the perfect tankless to replace a 40-gallon electric tank-style water heater to help you lower your energy bills.
  • 5-year heating module limited warranty.
  • Part of the Tronic 6000 line-up.

Atmor ThermoPro 27kW

Atmor AT-910-27TP ThermoPro 27kW/240V Electric Tankless Water Heater, 5.1GPM 112.3 Amps

We couldn't leave the Atmor ThermoPro off our list! This no-nonsense workhorse is capable of delivering up to 5.4 gallons of hot water every minute; enough to run two showers, two bathroom sinks, and one kitchen sink at the same time.

Even when the incoming water temperature is as low as 37°, the Atmor can deliver an impressive 2.6 gpm. The 27kW is the largest of the three ThermoPro models in Atmor's line-up, and requires three 40-amp double pole breakers.

The two heating modules allow the unit to maximize it's energy efficiency, and because the interior of the modules are stainless steel, they're resistant to corrosion and extremely durable.

The Atmor Thermopro is a solid performer and a great choice if you're looking for a whole house electric tankless water heater.

  • Up to 5.4 gallons of hot water every minute.
  • Performance to run 2 showers, 2 bathroom sinks, and 1 kitchen sink at the same time.
  • A great choice if you're looking for a whole house electric tankless water heater.

Man drawing gears on a glass board

How Does an Electric Tankless Water Heater Work?

Electric tankless water heaters work entirely differently than gas water heater systems. When a hot water tap is opened, cold water enters the tankless and the electric heating elements fire-up.

The water is heated as it passes through several chambers, and by the time the water leaves the tankless, it's hot and ready to serve the open faucet.

Electricity as a Fuel

The struggle between gas and electric tankless water heaters can be confusing. From a fuel source standpoint, electric units are far more efficient and typically reach 99% efficiency ratings! However, they are more expensive to operate.

Are Electric Tankless Water Heaters More Expensive?

Yes, you read that right. An electric tankless will be more expensive to operate than a gas unit, even though they are more efficient. This is because the current cost of electricity is higher than natural gas. 

Consistently, electricity prices are more stable than gas prices, and undoubtedly fuel prices will fluctuate in the future. However, most experts agree, that the price of electricity will likely increase at a much slower pace than gas.

Pen, paper, glasses and calculator

Advantages of a Tankless Water Heaters 

  • System and operformance not limited by the size of the tank
  • Tankless water heaters are capable of delviering constant, direct hot water
  • Operating costs are generally lower as you only use and heat the water when you need it

But Pay Attention to Flow Rate

Just because there isn't a tank to limit the amount of hot water the tankless unit can deliver, doesn't mean there aren't limitations. If you purchase a model with a flow rate that's below your household's hot water demands, your tankless won't be able to keep up, and you'll find your shower lukewarm!

Purchasing the correct sized unit is called sizing, and it's critical to your overall satisfaction. We'll show you how to properly size a tankless to meet your household hot water demand.

Light bulbs a row with one lit

Electric On-Demand Water Heaters

If you're looking for the best tankless water heater, then you owe it to yourself to take a close look at electric on-demand water heaters. Whether you're shopping for a whole-house system or a point-of-use unit, there are many advantages that make these systems a great choice.

Electric Fueled Tankless Water Heaters

There are a number of things to consider when shopping for a tankless water heater. And finding a unit that can keep up with your household's hot water needs should be at the top of your list.

But you should also consider and compare:

  • Warranty's 
  • Energy efficiency
  • Company's reputation

Tankless systems can last over 20 years if properly cared for, so it's important to do your research and find the right one for you and your family.

If you're not convinced that an electric tankless water heater is right for you, read our article on Gas vs Electric Tankless Water Heaters.

There are often tax credits and rebates available when you install a tankless water heater. Check to see if there are any incentives in your area.

How to Buy an Electric Tankless Water Heater

Electric on-demand water heaters are generally less expensive to purchase and install than gas systems. However, they do require a large amount of electricity to operate, and many homes aren't able to accommodate their energy requirements. 


Here are a few things to consider when buying an electric tankless water heater:

Price and Installation

  • Electric tankless water heaters are significantly less expensive than gas tankless systems. A quality electric tankless can be purchased for $500 to $700.
  • Many homes are not built to provide the electrical requirements these units need to operate. Installation expenses will significantly increase if an upgrade is needed to the home's electrical system.
  • Since exhaust gases aren't produced, venting is not necessary.
  • Electric tankless units are inexpensive to install, unless the household electrical system needs to be upgraded.
  • Since venting isn't necessary, an electric tankless system can be installed in many locations unavailable to a gas system.
Stiebel Eltron 36 Plus Tempra, Tankless Water Heater, White


  • Because of their simplistic design, electric units are easier to troubleshoot, diagnose and repair. In addition, they have a longer service life than gas units.
  • Electric tankless systems are about a third the size of gas units.
  • An electric tankless requires far less maintenance than a gas system. 

Energy Efficiency 

  • Extremely energy efficient. Over 98% of the incoming electricity is used to heat the water. (A gas unit may peak in efficiency in the mid 80's).
  • Requires a substantial amount of electricity to operate.
  • Since no greenhouse gases are produced, electric systems are very environmentally friendly.
Holding an electric wire

How to Size an Electric Tankless Water Heater

Selecting the right size tankless water heater (known as sizing) for your household's hot water needs is a critical step when purchasing a tankless. At first, it may seem like an overwhelming and difficult task, but actually it's relatively easy.

> > Read our guide on How to Size a Tankless Water Heater < <

There's two calculations you'll need to determine in order to size a tankless water heater. Once you know these numbers, you'll be able to find the right sized unit to meet your family's hot water needs.


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Temperature Rise - The temperature rise is simply the difference between the incoming ground water temperature and the heated output temperature.

Flow Rate - This is the amount of water a tankless water heater is capable of heating at any give time. The flow rate is measured in gallons per minute (GPM).

There's no shortage of unsatisfied tankless water heater owners who failed to properly size their new unit. If you purchase a tankless unit that's too small, it won't be able to meet your hot water needs.

By taking a little time upfront, before you purchase your system, you'll save time, frustration, and money in the future. And you’ll have a better chance of getting the best electric tankless water heater for your home.

Bosch Electric Tankless Water Heater - Eliminate Time for Hot Water - Easy Installation

Finding the Right Size Tankless Water Heater

Step 1: Peak Demand

The first thing you need to know is your home's peak demand flow rate. This isn't as difficult as you might think. To begin with, determine when your household uses the most hot water. In most homes this is in the morning when your family is showering, shaving, and getting ready.

Calculate the Gallons per minute (GPM) of each hot water device you'll use at any one time. Do you run the dishwasher? How many showers are being used? Is the washing machine used?

Jot down which fixtures are being used during the peak demand and then determine their flow rate. Here's a few general guidelines:



Washing Machine

1.0 - 1.5 GPM


1.0 - 2.0 GPM

Bath Tub

4.0 GPM

Water-Saver Shower Head

1.5 GPM

Standard Shower Head

2.0 GPM

 Hand Sink

0.5 GPM

 Kitchen Sink

1.0 to 2.0 GPM

*Consider any other appliances you many be using during peak times. Such as washing machines and dishwashers. (Data from Rheem)

Then, add each GPM to find your peak demand flow rate. As an example: 1 shower (2.0 GPM) + 1 hand sink (0.5 GPM) = peak demand: 2.5 GPM

Step 2: Temperature Rise

Your next step is to determine the temperature rise. To do this you'll subtract the ground water temperature (water entering your house) from your desired output temperature (hot water temperature).

>>Use this chart to determine the ground water temperature in your area <<

Here's an example of how to find your temperature rise: Ground water temperature 50 degrees <minus> output temperature 120 degrees <equals> a temperature rise of 70 degrees F. (120 - 50 = 70).

In other words, your tankless water heater will need to heat the incoming water 70 degrees (temperature rise) in order to reach your desired hot water temperature of 120 degrees.


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Step 3: Buy Your Tankless

Now that you've calculated your required Flow Rate and Temperature Rise, you can use this information to select the tankless model that best meets your needs.

Manufacturers use the terms Flow Rate and Temperature Rise to properly size their models, so you'll be able to compare one model against another and know exactly how it'll perform in delivering hot water to your household.

Watch the Video:

Man shrugging will looking at a set of scales

Comparing Tankless Systems

There are several critical factors to consider when comparing tankless systems. First and foremost, you need to make sure your home's electrical system is capable of handling the energy demand.

Electrical Demands

Electric tankless water heaters require a substantial amount of electricity. If you're looking at a tankless that draws 150 amps and your home's electrical service panel is only capable of 100, your home is simply not equipped to handle the load.

If this is your situation, there are several options. You could upgrade your home's electrical, purchase a less powerful unit, or invest in a gas tankless system instead.

Stiebel Eltron 36 Plus Tempra, Tankless Water Heater, White

The Stiebel Eltron Tempra 36 Plus draws 150 amps. However, the Stiebel Eltron Tempra 20 Trend draws only 80 amps. Click HERE to Learn More.

Delivering Enough Hot Water

Once you've determined your peak hour flow rate, it's time to find a tankless system that can meet the demand. In the chart below, we've compared the largest models, but each manufacturer offers smaller units within the same product line.

Your ultimate goal is to find the right size tankless system to meet your household hot water needs, not to simply purchase the largest model. If you only require 2.5 gallons of hot water per minute, there's no need to pay the extra money and buy a unit that's capable of delivering 6.0 gpm.

Ecosmart ECO 36 36kw 240V Electric Tankless Water Heater

The EcoSmart ECO 36 delivers 5.46 gpm of hot water at a temperature rise of 45-degrees. However, the EcoSmart ECO 27 can deliver 3.64 gpm at the same temperature rise, and it's about a hundred dollars cheaper! Click HERE to Learn More.

Measuring Efficiency

A water heater's efficiency is measured through a rating system called the Uniform Energy Factor. Prior to 2017, efficiency was calculated using the Energy Factor (EF) rating.

The UEF allows consumers the ability to make an "apples-to-apples"  comparison between one brand of water heater to another. It also allows for a more accurate measurement of how the appliance will perform in real world scenarios.

Most electric tankless water heaters have UEF ratings in the upper mid-90's. The higher the number, the more energy efficient the water heater.

Rheem 240V 4 Heating Chambers RTEX-36 Residential Tankless Water Heater

The Rheem RTEX-36 has a UEF rating of 99.8, which is one of the highest ratings in the industry! Click HERE to Learn More.


As with most appliances, warranties vary from manufacturer-to-manufacturer. In addition, there's different requirements necessary to activate warranty coverage, so reading the fine print is critical.

It's not uncommon for manufacturers to require a tankless unit to be registered and in addition, be professionally installed in order for the warranty to be valid.

Company's that provide solid warranties without alot of fine print, are basically making a statement to the consumer that they have confidence in their product.

Although each manufacturer is different, some common coverage ranges include: 5 to 7-years of coverage for the heat exchanger; 1 to 2-years for parts; and 1-year of labor.


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Wrench on a table

Electric Tankless Heater Maintenance

Since electric tankless water heaters don't "burn" fuel like a gas tankless, combustion isn't required to heat water. Because of this, electric systems run cleaner than gas systems . . . and cleaner means less work for you!

With less maintenance than gas heaters, and a simplistic design, they'll not only require less attention, but they'll also typically have a longer service life.

Water Quality

Your electric tankless water heater is at the mercy of the quality of water that flows through it's system. Taking the following three proactive measures will ensure that your tankless is running in peak condition. With a little care, your electric ondemand system will provide you with years of loyal service.

Most manufacturer warranty's do not cover issues related to poor water quality. Taking a proactive approach to maintaining your electric tankless system will help ensure it has a long and healthy service life

Regular Flushing

Unfortunately, electric tankless water heaters are not immune to limescale build-up. As water is heated, the minerals separate and form a scaly layer within the heat exchangers, heating elements and other metal parts.

As the limescale build-up increases, the tankless unit will be required to work harder in order to heat the water, thus reducing it's efficiency and increasing your electric bill.

The added wear-and-tear can create costly repair expenses and shorten the system's service life. Flushing is not difficult and your owner's manual will have details for your specific unit.

Install a Sediment Filter

Your tankless system has a small screen on the water inlet to filter out any incoming sediment before it enters the unit. Called a water inlet screen, it should be flushed periodically to remove any collected debris.

Many homeowners rely solely on the water inlet screen to protect their tankless system. However, this is a dangerous gamble. We highly recommend installing a sediment filter on the incoming water line.

DuPont WFPF13003B Universal Whole House 15,000-Gallon Water Filtration System

DuPoint's Whole House Water Filter is capable of filtering 15,000 gallons of water with each filter change. Click HERE to Learn More.

A sediment filter will filter out the debris before the water enters the tankless unit. Think of sediment filters as an inexpensive insurance policy for your water heater. Even better, install it so that it can filter all incoming water and you'll protect all of your water-use appliances.


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Install a Scale Inhibitor

Installing a scale inhibitor or water softener goes hand-in-hand with flushing your tankless system. The only difference is, flushing removes the limescale, and a scale inhibitor helps prevent limescale from forming in the first place.

Installing a water softener or scale inhibitor doesn't mean that you'll never need to flush your tankless, but it will undoubtly extend the time between flushes.

Many people live in areas where the water is especially hard and a water softener is all but required. But even if you don't struggle with hard water, installing a simple scale inhibitor can be a good move.

We like the one made from 3M. It can be installed for your whole house to protect your plumbing, tankless, and other water-use appliances. It's capable of handling a flow rate of up to 10 gallons per minute, and once installed, you simply unscrew the cartridge to replace it with a new one. 

3M Aqua-Pure Whole House Scale Inhibition Inline Water System AP430SS, Helps Prevent Scale Build Up On Hot Water Heaters and Boilers

3M's Aqua-Pure Scale Inhibitor helps reduce limescale build-up in household plumbing, water-use appliances, and water heaters. Click HERE to Learn More.

Electric light bulbs

Electric Tankless Water Heater Buyer's Checklist

Purchasing a tankless water heater is an investment. If properly maintained, a tankless can have a service life over 20 years. So spending extra time upfront before you select a model, is time well spent. Here are a few thought starters to consider:

Fuel Checklist

  • Will your home have enough electrical power to operate an electric tankless water heater? Or will you need to upgrade your electrical system?
  • Electric fueled heaters don't emit green house gases. In addition, they're far more energy efficient than gas systems.
  • Gas fueled tankless water heaters tend to produce a higher flow rate than electric units.

Climate Checklist

  • Cooler water = Lower GPM. The cooler the incoming water temperature, the higher the GPM rating you'll need to purchase. Be sure to match your incoming water temp to your geographical location.
  • Incoming water temperature is cooler in the winter and warmer in the summer. When selecting your tankless, it's a good idea to purchase a more powerful water heater that can deliver the results you need during the winter.

Safety Issues and Requirements

  • Many manufacturers require their tankless water heaters to be professionally installed in order to validate the warranty.
  • Having your new tankless water heater professionally installed will ensure that it'll be eligible for the manufacturer's warranty. Plus, you can rest at ease that all the necessary requirements and building codes were met.
  • Most manufacturers provide detailed installation instructions. Still, we strongly recommend hiring a professional to install your new water heater.

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Last update on 2022-11-23 / Affiliate links / Images from Amazon Product Advertising API

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