Shower and electric water heater in the bathroom

5 Best Tankless Water Heaters (2021 Reviews)

Homeowners around America and around the world have been wondering how to heat up the water in their homes since the beginning of time. This can be easily taken care of with heat exchanger technology in tankless water heaters, with which you can choose the heat of your water (you can use them in Celsius or Fahrenheit) and heat several different fixtures in your home. If you want to learn more, you can check out this article by How Stuff Works on tankless water heaters.There will also be a more thorough section on how they work at the end of this list. Several tankless water heater reviews have resulted in this ultimate buying guide. All of these are electric models since those seem to be the most high-quality and the most popular. So, are you ready to get started?!

In a hurry? Here’s the test winner after 10 hours of research:

Overview
Ecosmart ECO 36 36kw 240V Electric Tankless Water Heater
Title
Ecosmart ECO 36 36kw 240V Electric Tankless Water Heater
Price
$599.00
Rating
Overview
Ecosmart ECO 36 36kw 240V Electric Tankless Water Heater
Title
Ecosmart ECO 36 36kw 240V Electric Tankless Water Heater
Price
$599.00
Rating

5 Best Tankless Water Heaters Reviews of 2021 – Overview

Overview
Best Overall
Ecosmart ECO 36 36kw 240V Electric Tankless Water Heater
Rheem RTEX-18 18kW 240V Electric Tankless Water Heater, small, Gray
Rheem 240V 4 Heating Chambers RTEX-36 Residential Tankless Water Heater, GRAY
Lowest Price
Marey Power Pak Plus Tankless Electric Water Heater, 220 VOLT
Stiebel Eltron 239223 Tankless Water Heater – Tempra 29 Plus – Electric, On Demand Hot Water, Eco, White, 23
Title
Ecosmart ECO 36 36kw 240V Electric Tankless Water Heater
Rheem RTEX-18 18kW 240V Electric Tankless Water Heater, small, Gray
Rheem 240V 4 Heating Chambers RTEX-36 Residential Tankless Water Heater, GRAY
Marey Power Pak Plus Tankless Electric Water Heater, 220 VOLT
Stiebel Eltron 239223 Tankless Water Heater – Tempra 29 Plus – Electric, On Demand Hot Water, Eco, White, 23
Price
$599.00
$412.00
$825.00
$145.69
$621.81
Rating
Best Overall
Overview
Ecosmart ECO 36 36kw 240V Electric Tankless Water Heater
Title
Ecosmart ECO 36 36kw 240V Electric Tankless Water Heater
Price
$599.00
Rating
Overview
Rheem RTEX-18 18kW 240V Electric Tankless Water Heater, small, Gray
Title
Rheem RTEX-18 18kW 240V Electric Tankless Water Heater, small, Gray
Price
$412.00
Rating
Overview
Rheem 240V 4 Heating Chambers RTEX-36 Residential Tankless Water Heater, GRAY
Title
Rheem 240V 4 Heating Chambers RTEX-36 Residential Tankless Water Heater, GRAY
Price
$825.00
Rating
Lowest Price
Overview
Marey Power Pak Plus Tankless Electric Water Heater, 220 VOLT
Title
Marey Power Pak Plus Tankless Electric Water Heater, 220 VOLT
Price
$145.69
Rating
Overview
Stiebel Eltron 239223 Tankless Water Heater – Tempra 29 Plus – Electric, On Demand Hot Water, Eco, White, 23
Title
Stiebel Eltron 239223 Tankless Water Heater – Tempra 29 Plus – Electric, On Demand Hot Water, Eco, White, 23
Price
$621.81
Rating

 

Best Overall
1. Ecosmart ECO 36 36kw 240V Electric Tankless Water Heater

Sale
Ecosmart ECO 36 36kw 240V Electric Tankless Water Heater
408 Reviews
Ecosmart ECO 36 36kw 240V Electric Tankless Water Heater
  • Sleek and compact design with digital output temperature display

The Ecosmart ECO 36 36kw 240V Electric Tankless Water Heater is a lovely Ecosmart product. It is the absolute best on the market. It is incredibly budget-friendly and quite a high-quality tankless water heater. It is 99.8 percent energy-efficient, so you will be able to save both energy and money (and also, the environment). It has a sleek and compact design with a digital output temperature display so you can change the temperature to whatever you would like. This tankless water heater is also 100% made in the USA and comes with a generous limited lifetime warranty.

If your home is in a place with a warmer climate, then the water flow rate on this tankless unit will be 9 GPM (gallons per minute) so you will have a great supply of hot water. However, if your home is in a colder climate, then the GPM flow rate will drop to 3.6 gallons per minute. This product will come equipped with 3/4 inch NPT pipe fittings for an easy and smooth installation and powerful water heating power.

 

Features of the Ecosmart ECO 36 36kw 240V Electric Tankless Water Heater:

  • Best on the market
  • Great price-to-quality ratio
  • Eco-friendly
  • A capacity of 9 GPM in warm climates
  • A capacity of 3.6 GPM in colder climates
  • 99.8 percent energy efficient
  • High-efficiency product
  • High energy savings
  • High durability
  • Sleek and compact design
  • Digital output temperature display
  • Made in the USA
  • DIY installation possible
  • Pipe fittings are 3/4 inch NPT
  • Comes with a limited lifetime warranty

 

2. Rheem RTEX-18 18kW 240V Electric Tankless Water Heater

Rheem RTEX-18 18kW 240V Electric Tankless Water Heater, small, Gray
715 Reviews
Rheem RTEX-18 18kW 240V Electric Tankless Water Heater, small, Gray
  • External digital thermostatic control with LED display (+/1 degree accuracy)

The Rheem RTEX-18 18kW 240V Electric Tankless Water Heater is a reliable tankless water heater. This product boasts a water flow rate of 4.4 GPM (gallons per minute) as well as advanced self-modulation technology that will use more power when heating demands it and conserve energy when the demand drops, making it quite an energy-efficient product. This tankless hot water heater is said to reduce the need for electricity in your home by 50 percent.

This tankless water heater will come equipped with two durable copper immersion heating elements, as well as an external digital LED display with thermostatic control. That means that you are also able to adjust the temperature to your needs with this product with an accuracy of ±1°F. This tankless water heater is very easy to install and comes equipped with 3/4 inch NPT water connections. There are no batteries required for this product. In terms of the warranty, you will have a one-year warranty for your parts and a five-year warranty for the heating chamber.

There are a few problems with this tankless water heater. If it is plugged into too many fixtures, this product might lose some efficiency, both in terms of heating power and water flow rate. Lastly, this is not the most budget-friendly option on the market, meaning that if you and your family are on a tight budget, then this might not be the best option for your home.

 

Features of the Rheem RTEX-18 18kW 240V Electric Tankless Water Heater:

  • Advanced self-modulation that uses more power when heating demands it and conserves energy when demand drops
  • A water flow rate of 4.4 GPM
  • Reduces the need for electricity by 50 percent
  • Great energy efficiency
  • External digital thermostatic control with a clear LED display
  • Durable dual copper immersion heating elements
  • A five-year warranty for the heating chamber
  • A one-year warranty for parts
  • Easy to install
  • 3/4 inch NPT water connections
  • Might lose efficiency if plugged into too many fixtures
  • Not a very budget-friendly option
  • High price tag
  • Batteries not required

 

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

Rheem 240V 4 Heating Chambers RTEX-36 Residential Tankless Water Heater, GRAY
51 Reviews
Rheem 240V 4 Heating Chambers RTEX-36 Residential Tankless Water Heater, GRAY
  • External digital thermostatic control with LED display (+/1 degree accuracy)

The Rheem 240V 4 Heating Chambers RTEX-36 Residential Tankless Water Heater is another Rheem product that is very similar to the tankless water heater above, except on a bit of a larger scale. As with the product above, this water heater comes equipped with an external LED digital display so you can change the temperature of the water coming out of your faucet, an advanced self-modulation system that will save you energy (will reduce its need by 50 percent), and four (instead of the two in the product above) copper heating immersion elements that will power the hot water in your home.

This tankless water heater is very easy to install and when you buy this product, you will receive 3/4 inch NPT water connections so you can put it together yourself with ease. Similar to the other Rheem product on this list, there is no need for batteries with this water heater. This system has a warranty of five years for the heating chamber ad a warranty of one year for parts. Although this is a fairly compact unit, it does require 150 amps in order for it to run, making it not an especially accessible product for certain households. It is also a bit of an expensive product, which is another reason it might not be completely accessible to every home.

 

Features of the Rheem 240V 4 Heating Chambers RTEX-36 Residential Tankless Water Heater:

  • Four copper heating immersion elements
  • Advanced self-modulation system
  • Reduces the need for electricity by 50 percent
  • External digital display with the LED readout
  • Compact unit
  • Easy installation
  • 3/4 inch NPT water connections
  • Warranty of five years for the heating chamber
  • Warranty of one year for parts
  • Requires 150 amps to run which might not be accessible to every home
  • More expensive than other models
  • Batteries not required

 

Lowest Price
4. Marey Power Pak Plus Tankless Electric Water Heater

Sale
Marey Power Pak Plus Tankless Electric Water Heater, 220 VOLT
116 Reviews
Marey Power Pak Plus Tankless Electric Water Heater, 220 VOLT
  • Allows customer to regulate energy consumption, adapting the product to the home’s electric capacity

The Marey Power Pak Plus Tankless Electric Water Heater is another budget-friendly option on this list. This tankless water heater is very easy to install and very easy to use, which makes it quite an attractive product. It will save you up to 60 percent on electricity too, making this product not only budget-friendly, as mentioned, but also an eco-friendly option. This water heater can be used with two fixtures at the same time in hot climates or it can be used with one fixture only in cold cor moderate climates. The only downside to this product is that it does not have enough power to heat up a bathtub for a bath, since baths have a higher flow rate and demand a higher amount of water than showers, and this tankless water heater might not be able to heat up the water fast enough, so you will not have enough hot water to fill your tub.

The best part about this tankless water heater is that it comes with a water filter. Water filters are a great way of making sure both your drinking water and your tap water is clean and pure. A water filter can get rid of lead, chlorine, bacteria, calcium, minerals, salt, carcinogens, and more. This can be especially useful if you live in a place with notably bad quality water, or simply if you are worried about tap water in general and you just want to get the best quality water possible for yourself and your family. This is a smaller tankless water heater that is ideal for smaller homes that want the added benefit of a water filter system.

 

Features of the Marey Power Pak Plus Tankless Electric Water Heater:

  • Budget-friendly option
  • Easy to install
  • Easy to use
  • Low energy factor
  • You will save up to 60 percent on electricity
  • Comes with a water filter
  • Can be used with two fixtures at once in hot climates
  • Can be used with one fixture in cold/moderate climates
  • Does not have the capacity to heat a bathtub for a bath

 

5. Stiebel Eltron Tempra Plus 29 kW Electric Tankless Water Heater

The Stiebel Eltron Tempra Plus 29 kW Electric Tankless Water Heater is a great product from a famous and reliable German brand, which has been about for nearly 100 years. This tankless water heater requires no batteries and no venting (there will be no vent element with this product). It is a compact and sleek product that will save you space. Its self-modulation technology should be able to save you anywhere from 15 to 20 percent in electricity use. It has advanced flow control technology, although, despite this, the water flow might still lower if demand exceeds supply. As with some of the other products mentioned on this list, this water heater might have some trouble running if it is plugged into too many fixtures at once in the winter in cold climates.

The most problematic element with this tankless water heater is that it requires a very real amount of electrical work in order to get it up and running. Essentially, this product requires a hard-wired 240 or 208-volt electric service, with a maximum draw of 28,800 watts at 240 volts or 21,600 watts at 208 volts. It also requires 3 separate dedicated 40 amp breakers with 8 gauge copper wiring and a minimum of 200 amp total service to the residence, so if you are not able to provide these or understand how they work, then you might have to call someone that will be able to do it for you, such as a plumber, which will raise your installation costs.

 

Features of the Stiebel Eltron Tempra Plus 29 kW Electric Tankless Water Heater:

  • Advanced flow control technology
  • Reduces flow slightly when demand exceeds supply
  • Self-modulation technology
  • Reduces 15 to 20 percent of electricity use
  • The sleek design saves space
  • There is no venting required
  • No batteries are needed
  • It will require a certain amount of electrical work in order to install it
  • Might struggle with running several fixtures at once in winter in cold climates

 

Our Winner:

Overview
Ecosmart ECO 36 36kw 240V Electric Tankless Water Heater
Title
Ecosmart ECO 36 36kw 240V Electric Tankless Water Heater
Price
$599.00
Rating
Overview
Ecosmart ECO 36 36kw 240V Electric Tankless Water Heater
Title
Ecosmart ECO 36 36kw 240V Electric Tankless Water Heater
Price
$599.00
Rating

The Ecosmart ECO 36 36kw 240V Electric Tankless Water Heater is the winner in the tankless water heater category. It has the absolute best price-to-quality ratio on the market, a sleek and compact design, a great digital output temperature display, and a fantastic ability to be 99.8 percent energy-efficient. This tankless water heater will save you money, energy, and even the environment and it is our absolute favorite on this list.

 

How Do Tankless Water Heaters Work?

 

Tankless water heaters heat water without a storage tank, unlike tank water heaters. They use natural gas such as propane (these are called propane tankless water heaters) coming from your gas line or a heating element in order to create a temperature rise in the incoming water temperature, which is often cold water, in order to meet your hot water demands. Gas models, or gas tankless water heaters, can lower your energy costs and utility bills, but they can also cause more emissions to the environment.

In contrast to gas units, tankless models that rely on heating elements can be more eco-friendly. There are some tankless hot water heater systems that are good for your whole house, but most will be unable to service all of your faucets at once, meaning you might not be able to get hot water coming from your showerhead and in your washing machine at the same time. One last note to add: stainless steel units often have higher lifespans than other types of models.

 

Bonus Tip: Check out this cool video that goes through the basics of tankless water heaters and how they work.

 

 

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Joshua Perkins

Joshua spent ten years as a water systems technician in California before settling down with his wife and two young children in Nashville in 2018. Through all of his experience, he learned the benefits and shortfalls of so many different types of water filtration systems, from pitchers to whole-house installations. He started Water Filter Authority in 2019 to empower other families to make the right decision for their long-term health and wellness.