6 Most Efficient Electric Tankless Water Heater Reviews & 2021 Guide

most energy efficient electric hot water heater

Buying and installing the most efficient electric tankless water offer you with the constant hot water, low energy costs and improves the resale value of your family. While it is shaping our way of life with brilliant working performance, by simplifying the method of acquiring constant hot water; the search of the best types is difficult.

Here we embark on the trip to hunt down the best types on the market. Analyzing the brands’ history, products energy costs, quality levels, and after-sale service, the following types listed on our most efficient electric tankless water heater reviews are of the most worth buying product.

Apart from the products reviews, there is also basic knowledge on energy costs of electric and other types of tankless water heaters you can never miss.

Here we go!

Top 6 Most Efficient Electric Tankless Water Heater

efficient gas hot water heaterEcoSmart ECO 11 Heater4.8
most energy efficient gas water heaterStiebel Eltron 224199 Water Heater4.8
most efficient electric tankless water heaterMarey ECO Self-Modulating Heater4.6
super efficient electric water heaterRheem 240V RTEX-13 Heater4.5
best energy efficient water heaterEcotouch Electric Water Heater4.3
efficient electric heaterStieble Eltron 24 Plus Tempra4.3

Most Efficient Electric Tankless Water Heater Reviews

1. The Most Efficient Electric Tankless Water Heater – EcoSmart ECO 11 Heater

efficient gas hot water heater



【Energy saving】

Features the self-modulating technology, this unit adjusts the water flow rate and power based on the amount of water needed, so as the heating and energy costs are reduced at least 50%. It heats water only when the machine turns on, leading to less heating loss.

【Ideal for small apartment】

The compact size fits the small corner of your home, spares wall and floor space for small apartment use. By heating up to 2 gallons of minute water, you can use it as the point of use or for one shower use. Stable and constant hot water brings along satisfying user experience. In warm regions, you can also use one shower and one sink at the same time.

【Easy to operate】

EcoSmart follows the brand principle and sticks to produce heaters that are of eco-friendly. Plus, the design of the machine is also simple and modern, adds up your home decor when installing it in the bathroom or around the water sink. The LCD display shows the exact water temperature, and the buttons below enable you to adjust the temperature by 1 increment a time.

2. Runner Up – Stiebel Eltron 224199 Water Heater

most energy efficient gas water heater



【Advanced flow control】

Being the successor of Tempra series, Tempra Plus has big boots to fill. The shining feature of it is the advanced flow control, which maintains the water temperature to keep it stay hot no matter how many devices run at the same time. Once demand hot water exceeds the capacity, the system reduces the flow to remain stable temperature.

【Digital temperature control】

The LCD screen shows the exact water temperature with 1-degree increment. Being the leader of the tankless water heater market for around 90 years, this German design with its products lines are still gaining praise because of their brilliant performance.

【Small and compact shape】

As big as a briefcase, it requires a modicum of storage space in your bathroom. The sleek design coordinates perfectly with any home decor, especially those of modern type. Unlike a tank water heater, it never runs out of hot water. The total silent operation brings along smooth and perfect user experience.

3. Best Point of Use Energy Efficient Heater – Marey ECO Self-Modulating Heater

most efficient electric tankless water heater



【Multiple point of use】

This unit is ideal for two points of use simultaneously when you live somewhere warm in southern parts of America. While in cold regions, it is suitable for a sink around 1.3 gallons per minute. Activated by low water pressure, it provides constant hot water the moment faucet is opened.

【Energy efficient】

When comparing this machine with conventional heaters, it saves around 60% on energy costs. Its unique ECO line maintains a 98% efficiency level during its whole using life. If under careful maintenance, the life span of the heater prolongs long enough to get great bang for the buck.

【Cheap price】

Costs no more than $200, you can get this advanced point of use heater home. The German-designed system with stainless steel interior material keeps it durable and long-lasting. Adjusting the water temperature is super easy, under the help of LCD display, you can adjust the temperature with 1-degree increment.

4. Hot Selling Energy Efficient Tankless Water Heater – Rheem 240V RTEX-13 Heater

super efficient electric water heater



【Heavy-duty material】

The durable copper adopts on the machine prolongs the service life of the machine, the non-corrosion design enables it to be durable and long-lasting. With an average life span of around 10 years, this machine is well worth the price.

【Digital panel control】

The external digital panel control makes it easy to operate in adjusting the water temperature. By turning the buttons from left to right, you can drop or increase the water temperature with 1-degree increment, showing on the LCD display panel.

【98% energy efficient】

Passing through the standard of electric tankless water heater, this unit promotes its energy efficiency to as high as 98%, letting no standby loss of the heat, and reducing your energy costs accordingly. Plus, the installation of the machine is super easy, follow the instructions and you can do it all by yourself.

5. Cheap Energy Efficient Tankless Water Heater – Ecotouch Electric Water Heater

best energy efficient water heater



【Instant hot water】

Being the cheapest electric energy efficient instant water heater, the performance of which stays equally balanced as the high-end types. Using under the power of 5.5KW, it provides you with hot water that never runs out. The moment you turn on the tap, hot water flows out and there is no more need to waiting so long for hot water any longer.

【Advanced self-adjustment】

The smart self-adjustment shines in balancing the water temperature through monitoring the flow rate and temperature setting. The optimal design proves to save around 98% on energy efficiency, leading to low costs on water and energy bills.

【Multiple protection devices】

Equipped with multiple protection devices, this unit ensures using safety. The separated inner water and electricity lines design keeps the interior materials away from being leakage or corrosion, which prolongs the lifespan of the machine.

6. Heavy-duty Energy Efficient Tankless Water Heater – Stieble Eltron 24 Plus Tempra

efficient electric heater



【Digital display】

The German-designed unit keeps it the leading position in performance and quality level. The large flow rate supports constant hot water for whole house use. Winning the highest standard level, it promises a long life span of the machine.

【Advanced flow control】

Applied with advanced flow control, it features stable hot water temperature. By adjusting the power based on the water flow rate and amount of water needed, it offers a comfortable bathing experience. The pre-set buttons allow you to get the wanted temperature according to your habit.

【0.99 energy efficient】

The energy efficiency of the unit reaches 99%, much higher than conventional types and even higher than other energy-efficient models. Thanks to its self-modulating technology, the hot water flows out only when you need it, thus more energy is saved.

Don’t want an electric tankless water heater? Then you can go on reading, for we have picked out several energy-efficient gas and propane tankless water heaters for you as follow.

Most Energy Efficient Gas Water Heater Reviews

1. Outdoor Gas Tankless Water Heater – Rinnai RU98EN Ultra-NOx Condensing Heater

most energy efficient electric water heater



【Low NOx design】

Unlike other gas water heaters spending much money on energy costs, the low NOx design of this unit meets the NOx Emissions Standard of California and Texas, which is highly environment-friendly and spares more money in energy costs as well as electricity costs.

【Ultra efficient】

This Rinnai tankless water heater benefits in high energy efficient with its condensing design. The unused gas and heat are recovered, leading to the reduction on standby loss.

【Outdoor installation】

The venting facilities are the essential devices for natural gas heaters, serving for emitting wasted gas during the use. The outdoor installation, however, saves the expense by letting the wasted gas and heat gone naturally.

2. Large Flow Rate Energy Efficient Gas Water Heater – Rinnai V94IN Heaters

most efficient tank water heater



【9.4 GPM flow rate】

The maximum flow rate of 9.4 GPM offers you the constant hot water. In summer regions, it is capable of supporting two showers use at the same time, while for cold regions, one shower and one sink can be properly used. For a middle-sized family and even for a family of 4, you can use it perfectly.

【App remote control】

It comes with mobile app control, allows you to control the water temperature and on or off remotely when turning the system into vacation mode. The timers and schedules shut off the machine automatically to save energy.

【Warranty guaranteed】

It features 12 months warranty for heat exchanger and 60 months for the parts, the limited warranty brings reassuring feeling in using the machine. Plus, the thoughtful after-sale service of Rinnai enables to solve the problem in time on the model you get.

3. Most Efficient Propane Water Heater – Rinnai V94EP Heater

efficient hot water heater



【Outdoor Installation】

The outdoor installation of the propane tankless water heater frees you from getting venting facilities. The wasted gas is emitted directly out of the house, which not only saves expense in adding venting devices but also improves the using safety of the machine.

【9.4 GPM flow rate】

9.4 gallons per minute large flow rate supports middle and large family use on two showers in hot regions, and one shower and one sink in cold regions. There are also multiple models in different flow rate that are available based on your needs.

【Smart technology equipped】

It has smart mobile app control, allowing you to control the machine on and off with the vacation mode. To save energy and electricity, it also features timers to automatically turn off the machine when it is left unused for around 20 minutes for safety.

How Efficient is an Electric Tankless Water Heater?

Among electric, propane and natural gas instant hot water tankless water heaters, electric models tend to be the most energy-efficient type. The energy efficiency of gas and propane reaches around 80-85%, while the electric one reaches more than 98%, which refers to the low standby loss of heat.

You may also think in a simple way, the natural gas and propane tankless water heaters, as the name suggests, adopt gas as a power source to start the heating machine. For indoor installation, there must be venting facilities installed, why? Because of the waste gas it emitted. Some of the heaters with condensing design recovers the hidden heat that may have lost in conventional tankless water heaters, leading to the less loss of energy.

However, compared with gas heaters, the electric types use purely electricity as the power source, no venting devices needed and you do not need to maintain it regularly as natural gas types do. It proves that electric tankless water heater saves 24% – 34% money on using costs than traditional tank types. The life span of the electric models ranges around 20 years.

An Overall Look of the Energy Costs and Savings of Tankless Water Heater

In terms of the efficiency of the water heater, most people will ask, “Will the instant water heater costs much money? Are they expensive to install?”

Well, before purchasing the best types, the costs and savings are really the important factors to consider. If you are one of those paying great attention to the costs, here we give an honest breakdown.

Installation cost

Firstly, you should know that the installation costs on a tankless water heater are normally higher than conventional tank types.

The installation fee varies according to the types of heaters. For electric heating system, the installation expense is quite low, for you can basically do it by yourself only by following the instructions given by manufacturers, or to watch the video on YouTube.

Contrarily, the natural gas heaters, especially those supporting whole house use, are likely more expensive. They require a professional electrician to add additional wiring at home, and there are venting facilities you need to get. The overall costs on installation take around $500, of course, the exact price depends on where you live.

Energy savings

From the statistic on energy savings of tankless water heater vs. tank water heater, the anterior one wins in saving 15-40% energy. If you attempt to go with electric types, read the energy efficiency first, those with 95% or above are the ideal types to get.

The using costs of natural gas and electric on-demand water heaters are basically the same, but natural gas exceeds a bit.

Do Tankless Water Heaters Use More Water?

Not really. The major difference between tankless and tank water heater lies in the working principle. For the tank water heater, there is a storage tank aiming for storing cold water, and it heats the stored water once turning on the machine. Thus the waiting time for hot water is prolonged and you may have trouble in using hot water when you are busy going out.

The tankless water heater, also knows as an instant hot water heater or on-demand heater, outshines for its constant hot water supply, which means you can never run out of hot water if correct sizing is chosen.

Now get back to the problem, do tankless water heaters use more water? No! The amount of water they need in heating is the same, the major difference is by using instant hot water, you do not need to knock the bathroom door and get your kids to take a short shower for lack of enough hot water. Well, to such conditions, tankless water heaters do use more water during you are relaxed in the hot water bath.

How to Save Energy on Tankless Water Heater?

Does an Electric Tankless Water Heater Save More Energy Than Gas Type?

When you compare the prices of gas and electric tankless heaters, you will find the gas types much more expensive than an electric one, costs more than $500, some high-end types take around $1000 even. While its counterpart takes around $500-700.

In terms of operating costs, the electric heaters for its 98% energy efficiency exceed that of 85%. However, at a rule of thumb, the using costs of electric tend to be more expensive than gas, because of the high costs on electricity.

To sum up, the electric tankless water heater saves more energy than gas type, but the using costs tend to be higher than that.


Will Montgomery

Will Montgomery: Electro-Mechanical Engineer, Serial Entrepreneur, and Real Estate Enthusiast. Met David at Penn State, where he earned a BS in Electro-Mechanical Engineering and a minor in Business. Expertly manages capital equipment manufacturing, refurbishing, and repair businesses, while exploring opportunities in real estate and advocating for practical heating solutions.

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