Best Electric Tankless Water Heater Reviews & Buying Guides


Best Electric Tankless Water Heater

An electric tankless water heater which also called an on-demand water heater could be the best option for you who don’t prefer with the classic tank heather which requires more spaces and energy consumption.

This type of water heater is installed in a single appliance or under a sink to heat water directly. It heats the water as it passes through the unit. How is it better than a tank water heater? What are the factors to consider when purchasing a good one?

This article answers the above mentioned questions. It also features the best-selling tankless water heaters today. Does this device meet your heating requirements and cut your heating costs? Which one would you pick?

Our Best Electric Tankless Water Heaters Reviews

Product NameGPMWarranty
Stiebel Eltron Tempra1.5 – 4.57 years for leakage, 3 years for the parts
Sio Green2.5 – 4.02 years
EcoSmart ECO3.0Limited lifetime warranty
Rheem 2 RTEX-184.490 days
Bosch Electric Tankless1 – 1.55 years on the heating element, 1 year on other components

1. Stiebel Eltron Tempra

Stiebel Eltron TempraAvailable in various models with respective GPM and kilowatt requirements, this Stiebel Eltron Tempra offers functionality that suits different household heating and wiring specifications. For example, the Tempra 36 Trend requires a minimum flow of 0.77 gallons per minute to activate the unit and produce hot water between 86 to 140 degrees F.

This Tempra 36 Trend model comes with a digital temperature display for accurate temperature delivery and energy efficiency. The buttons allow you to control your desired temperature. It provides non-stop hot water and energy savings with 0.99 energy factor (EF).

All Stiebel Eltron Tempra models feature Advanced Flow Control that maintains desired water temperature to provide persistent warm water or hot shower whenever you need it. Made in Germany with high-standard heating technology, the Stiebel Eltron Tempra is one of the pioneers and trusted brands in the water heating industry.

The heavy-duty copper heating chambers heat and maintain hot water efficiently. This heating mechanism requires 12kW and 240V. Additionally, the sleek, portable built is more than aesthetics but for easy maintenance as well because it does not require venting. The unit may be one of the most expensive, but it comes with seven years of warranty for any leakage and three years for the parts which secure your purchase.

  • Advanced Flow Control feature for a continuous, unlimited supply of hot water
  • 1.4 to 4.5 GPM depending on the desired water temperature
  • Temperature digital display
  • Temperature buttons for accurate control
  • Silent operation with 0.99 energy factor
  • Heavy-duty copper heating mechanisms
  • Comprehensive warranty
  • Other models with varying features and costs available
  • Sleek design
  • Tested and certified lead-free compliant
  • The most expensive unit in the list

2. Sio Green

Sio Green SIO18 Electric Tankless WaterThe Sio Green is also available in five models each of which has different voltage requirements and features. All of them, however, are made with infrared heating mechanisms energized with quartz elements that don’t require contact with water. It doesn’t need periodic flushing to maintain the desired level of efficiency.

The carbon-coated heating element combined with quartz tubes generates far infrared energy to heat the water. Consequently, it amplifies the far infrared energy inside the quartz tube. This is the same technology the NASA developed for various high-temperature purposes.

Moreover, the quartz elements require no maintenance and venting. It is suitable for areas with hard water because it prevents calcium deposits and rust. It minimizes or prevents bacteria in the water. These elements are recyclable and contribute to superior heating efficiency and longevity.

The Sio Green has a maximum flow rate of 4.0 gallons per minute (GPM) for the 30-degree F temperature, 3.6 GPM for the 40-degree, 3.0 GPM for the 50-degree, and 2.5 GPM for the 60-degree heat. It is made with electronic modulating technology that calculates the difference between the current water temperature and the desired temperature to predict the required power. It uses 110 volts or 220 volts and heats only the water you need.

As an efficient tankless water heater, it has less than the 20-inch length that conveniently fits in compact spaces in the kitchen, bathroom, RVs, and sinks. The innovative design is also suitable for either residential or commercial purposes.

  • Far infrared ray and quartz heating mechanism
  • 2.5 to 4.0 GPM depending on the pre-set water temperature
  •  Prevents calcium build-up and rust
  • Suitable for areas with hard water
  • Can be for residential or commercial use
  • Can be installed in parallel, series, or hybrid mode depending on the required flow rate demand
  • Smart modulating technology that calculates the required energy to achieve the desired water temperature
  • Heaviest unit in the list
  • Quite expensive

3. EcoSmart ECO

EcoSmart ECO 27 Electric Tankless WaterIf you want that self-modulating technology that the first two products have, this EcoSmart ECO is a cheaper alternative. The ECO 27 model operates at 112.5 amps and 27kW at 240 volts. It can heat up to 3.0 GPM at 37 degrees F and has an activation flow at 0.3 GPM. The EcoSmart ECO comes in other models each with corresponding energy requirements and features.

The copper and stainless steel parts are durable, efficient, and easy to replace. They are all housed in a small unit to save storage and mounting space in kitchens, sinks, and other household areas. Additionally, the stylish and innovative design easily matches house interiors.

Moreover, the digital temperature control has increments of one degree. It allows you to control the temperature of incoming water according to particular needs. The ECO 27 utilizes only the amount of required energy based on the pre-set water temperature.

This mechanism helps save up to 50% of the heating costs. The EcoSmart ECO is one of the few units that come with a lifetime warranty. For its mid-range price and energy savings in the long-run, this unit is cost-effective and a must-have.

  • Advanced self-modulating technology that cuts power consumption
  • Heats water up to 3.0 GPM at 37 degrees F
  • Saves 50 percent in the energy consumption
  • Compact, stylish design
  • Lifetime warranty included
  • Can handle two sinks simultaneously
  • Digital temperature control with 1-degree increments
  • Easy-to-replace parts
  • Still expensive compared to other units in the heating industry

4. Rheem 2 RTEX-18

Rheem 240V 2 Heating Chambers RTEX-18Rheem may not be an expensive, top-quality brand in the water heating industry, but it delivers reasonable functionality and features. One of Rheem’s top-selling electric water heating machine is the Rheem 2 RTEX-18. At a lower cost, it offers unlimited hot water to residential and commercial establishments.

Just like the other units mentioned above, the Rheem 2 RTEX-18 has an external digital thermostatic regulator with LED display for accurate temperature control. The advanced self-modulation feature adjusts to the required energy to meet the user’s hot water demand.

The heavy-duty copper is made with two heating elements that deliver a flow rate of up to 4.4 GPM. The installation is relatively easy. The bottom has 3/4-inch NPT water connections and has a threaded construction for easy replacement.

The challenge, however, is its large dimensions which might take up too much space in the shower or under the sinks. For some homeowners, this minor drawback is probably not the factor they are concerned with especially if they have much space in these particular areas.

  • Not that expensive compared to the other units in the list
  • Unlimited hot water for residential and commercial purposes
  • Digital thermostatic regulator with LED display
  • Made with two heating elements that provide 4.4 GPM
  • Saves energy through the self-modulation function
  • Easy to install because of the threaded design and water connections
  • Effectively heats water in cold and warmer climates
  • Large dimensions which take up too much space
  • May come with an internal part failure
  • Possible temperature fluctuation
  • It takes a few seconds to heat the cold water up

5. Bosch Electric Tankless

Bosch Electric Tankless Water HeaterThe Bosch Electric Tankless is probably few of the cheapest electric tankless water heaters today. So, if you are the kind of homeowner with limited cash to spend on appliances, this unit is the perfect choice for you. However, it might not be as powerful as its expensive counterparts. The features included can compensate this drawback though.

The dimensions are compact, so it is easy to install. It can be conveniently and seamlessly mounted under the sinks and cabinet spaces. One thing that homeowners like about this unit is that it can also be an outdoor tankless water heater.

Notwithstanding the smart design that blends in well with the home interior, it can be installed on patios, garage, wet bars, and boats. The installation is easy. It can be mounted horizontally or vertically depending on the space available.

It operates at 220 volts and has an energy efficiency of up 98% with minimal standby loss. The flow rate is up to 1.5 GPM, and the water pressure range is 10 to 150 PSI. If this is enough for your hot water demand, then the Bosch Electric Tankless is the perfect, inexpensive product for you.

  • The most affordable unit in the list
  • Compact, lightweight, and attractive design that blends in well in home interior
  • Easy to install in small spaces
  • Can be mounted in outdoor areas such as kitchen patios and boats
  • Runs at 98% thermal efficiency
  • Weak hot water flow at 1.5 GPM
  • No thermostatic control and digital display
  • Doesn’t have a smart modulating feature

Is Tankless Water Heater Better Than Tank?

To answer this question, we will describe how each type of water heater works.

Storage tank water heater

The traditional water heating device is the storage tank water heater. The majority of households commonly uses it. It is made of an insulated tank that holds around 30 to 50 gallons of water. The heating mechanisms increase the water temperature and store it until it is needed.

A pipe is attached to the top from which the hot water passes through to various destinations such as bathroom, kitchen, and sinks. The heating power of storage tank water heaters usually comes from either electricity or natural gas.

The natural gas storage tank water heaters are typically expensive, but they utilize 50 percent less energy than the electric counterpart. They also have integrated valves for water flow control and temperature control. These valves open when either the pressure or temperature goes beyond the preset levels.

Tankless water heater

On the other hand, tankless water heaters are 24 to 34 percent more energy efficient than the storage tank water heaters for every 41 gallons (or less) hot water consumption per day. Homeowners that use around 86 gallons may enjoy energy savings of an additional eight to 14 percent.

One major drawback of the tankless water heater is it’s more expensive than the traditional storage water heater. However, it operates with less energy consumption, so you save money in the long run.

As the name implies, this type of water heater does not store water in a tank. Instead, it utilizes high-powered burners, usually gas or electricity, which promptly heat the water as it passes through a heat exchanger. Then, the hot water is instantly delivered to various household water channels such as faucets and showers.

There are other reasons why the electric tankless water heater is better than its traditional counterpart. Among them are the following:

  • Electric tankless water heaters last for seven to 10 years, and tankless gas heaters operate up to 20 years. On the other hand, the traditional storage tank models last up to 10 to 15 years.
  • They don’t consume too much storage space.
  • You won’t have to wait for 15 to 20 minutes to warm your water. These water heaters deliver two to four gallons of hot water per minute.
  • They generate hot water only when it is needed.

Things You Must Consider Before Buying an Electric Tankless Water Heater

If you are thinking about going tankless, then you should know how to determine a tankless water heater for your household. Not all of the marketed best-selling units as real as advertised. So, before you go to the store and purchase one, make sure you have in mind the essential factors to consider in a tankless water heater.

Incoming water temperature

The incoming water temperature can be pre-set through digital thermostatic control. Many tankless water heaters are integrated with this knob to set the desired water output temperature. A digital LED display of the heat is also available in many units.

It is also worth noting that the water temperature affects the water flow. For example, the 30-degree incoming water may have a water flow of up to 4.0 gallons per minute, while 60-degree water may flow at 2.5 GPM. We can claim that the higher temperature of the incoming water is, the lower its flow rate.

The initial cost for installation

Electric tankless water heaters cost from $90 to $900, and that does not include the installation costs. The first-time installation should be done by a professional, as it involves securing the vent, water, and electricity connection and make them leak-free. It also consists of upgrading the wiring and circuit-breaker panels.

If your home is already tankless water heater-ready or needs to replace an old tankless water heater, you can install it by yourself. Most tankless water heaters come with installation manuals and technical specifications to determine if it is the appropriate unit for your household.


Electric tankless water heaters have more parts than the traditional storage water tanks. This means that they have more tendencies for repairs and repair costs. Although many of the products come with a warranty, not all of them are comprehensive, and manufacturers are not immediately available to repair.

Durability is an important consideration. Some units are made with heating elements that don’t need periodic replacements and direct contact with water. Units made of quartz are ideal because they are long-lasting, rust-resistant, and suitable for hard water.


You may sign up for a professional to provide yearly annual maintenance service. The maintenance includes cleaning or changing the water and air filters and examining the electrical wirings and water flow.

In places with hard water, a vinegar flush is required every after 500 hours to remove mineral buildup and prevent it from clogging the unit. This task takes about 20 minutes and can be performed by the homeowner or a professional. You don’t need to do this if your water heater unit is made of quartz elements.

The Verdicts

We have presented the five comprehensive tankless water heater reviews. All of them are built with efficient heating mechanisms that save energy and power consumption. After thorough consideration, the EcoSmart ECO stands out among the list. Why not? It comes at a reasonable price that is loaded with practical functionalities and features.

The 4 GPM at 64-96 degrees or 3GPM at 49 degrees is more reasonable to expect and relatively sufficient. Although the EcoSmart ECO has long-lasting durability and construction, you have peace of mind for its lifetime warranty that most products in the water heating industry do not have. author Anastasia Russell
Anastasia is a 26-year-old blogger who always motivated to observe the ways humans interact with technology. She is currently undertaking a master degree program at the Uppsala University specializing in Human-Computer Interaction & Design Program.
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