Water heaters have been an essential solution for people’s hot water needs for decades. However with the development of technology, those big tanks that take so much space are becoming a thing of the past. In the following sections, we are going to dive into the world of tankless water heaters and try to help you find the best electric tankless water heater for your needs.

Did you know that you could have a water heater that takes up minimal space and still save up to 50% on your energy bill?

We will provide you with a dozen electric tankless water heater reviews as well as a buying guide in order to inform you about making the best choice. With our guide, you will be able to confidently make your own choice, whether you are looking for a continuous hot water supply or just a way to reduce your expenses.

EcoSmart ECO 11 Tankless Water Heater
  • Product: EcoSmart ECO 11
  • 4.1 Customer Rating
  • Price: $
  • Size (inches): 11.5 x 8 x 3.75
  • Weight(pounds): 7
  • kW @ 240V: 13
  • GPM @ 35 F Rise: 2,54
  • Amperage (amps): 57
  • Warranty for Parts(years): Lifetime
Stiebel Eltron Tempra 24 Plus 224199 Tankless Water Heater
  • Product: Stiebel Eltron Tempra 24 Plus 224199
  • 4.5 Customer Rating
  • Price: $$$
  • Size (inches): 21.7 x 20.1 x 9.6
  • Weight(pounds): 16,4
  • kW @ 240V: 24
  • GPM @ 35 F Rise: 4,68
  • Amperage (amps): 100
  • Warranty for Parts(years): 3
Rheem RTEX-13 Tankless Water Heater
  • Product: Rheem RTEX-13
  • 4.4 Customer Rating
  • Price: $
  • Size (inches): 4 x 9 x 13
  • Weight(pounds): 7
  • kW @ 240V: 13
  • GPM @ 35 F Rise: 2,54
  • Amperage (amps): 54
  • Warranty for Parts(years): 1
EcoSmart ECO 27 Tankless Water Heater
  • Product: EcoSmart ECO 27
  • 4.1 Customer Rating
  • Price: $$
  • Size (inches): 17 x 17 x 3.5
  • Weight(pounds): 14
  • kW @ 240V: 27
  • GPM @ 35 F Rise: 5,27
  • Amperage (amps): 112,5
  • Warranty for Parts(years): Lifetime
Stiebel Eltron Tempra 12 223420 Tankless Water Heater
  • Product: Stiebel Eltron Tempra 12 223420
  • 4.5 Customer Rating
  • Price: $$
  • Size (inches): 19.5 x 21.5 x 8.5
  • Weight(pounds): 13,5
  • kW @ 240V: 12
  • GPM @ 35 F Rise: 2,34
  • Amperage (amps): 50
  • Warranty for Parts(years): 3
Bosch US12 Tronic 3000 Tankless Water Heater
  • Product: Bosch US12 Tronic 3000
  • 3.4 Customer Rating
  • Price: $
  • Size (inches): 12.2 x 3 x 6.5
  • Weight(pounds): 6
  • kW @ 240V: 12
  • GPM @ 35 F Rise: 2,3
  • Amperage (amps): 50
  • Warranty for Parts(years): 1

Best Electric Tankless Water Heater Reviews

1. EcoSmart ECO 11

EcoSmart ECO 11 Tankless Water Heater

Space is often an important factor when installing appliances in your home, and this point-of-use tankless water heater saves space while being 98% energy efficient. Because of the compact design, you can easily mount the unit anywhere you want. Also, you control the whole thing with a digital display.

The power of this small unit comes to 11kW at 220V or up to 13kW at 240V. This may not seem as much, but it can get the job done. The minimum operating temperature for this model is at 80°F and this unit is effective with a temperature rise from 35 to 55°F. In this range, the flow output is between 2.54 GPM (@35°F rise) and 1.61 GPM (@ 55°F rise).

This means that the heater can support a shower and two faucets at its maximum heat potential, and even during the lowest temperature rise. The unit needs an electrical service of 125amps at a minimum, and the parts are covered by a lifetime warranty.

Read More: EcoSmart ECO 11

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2. Stiebel Eltron Tempra 24 Plus

Stiebel Eltron Tempra 24 Plus 224199 Tankless Water Heater

A well-known company like Stiebel Eltron usually delivers a solid product, as they have with this model. This self-modulating unit is marketed as a whole-house unit and it can just do that for a small household. Thanks to the German-designed Advanced Flow Control in this heater, 2 bathrooms can be supported at the same time in a warm climate, and 1-2 bathrooms in a cool climate.

The machine is 99% energy efficient but if you want to run it, you need a minimum of a 150-amp electric service with two separate 50-amp breakers dedicated for the unit. The energy needs of this unit are somewhere in the mid-range, but it will still save you money on your electric bill.

The warranty for this unit covers 7 years for leakage and 3 years for the parts. Because of the technology they put into this model, you can get hot water even when you go over its capacity, but at a reduced flow rate.

Read More: Stiebel Eltron Tempra 24 Plus

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3. Rheem RTEX-13

Rheem RTEX-13 Tankless Water Heater

The next unit on our list is one of the more budget-friendly models, which works nicely as a point-of-use tankless heater. The oval-shaped design is clean and compact. You can set the temperature you want with the single temperature dial and digital display.

The self-modulating technology is coupled with the dual copper immersion heating element that delivers a 99.8% energy efficiency rating. Though it may be small, this unit can support up to 2 low-flow shower heads at the same time. Also, the mounting and installation process is quite simple.

Since the energy load for this unit is just 54 amps, a 60-amp breaker would be the minimum required to cover it. Since it is so light and easy to mount, you could easily install it in your kitchen, RV or even a boat. The heat chamber for this model is covered by a 5-year warranty, while the other individual parts have a 1-year limited warranty policy.

Read More: Rheem RTEX-13

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4. EcoSmart ECO 27

EcoSmart ECO 27 Tankless Water Heater

Next on our list is one of the largest models made by the EcoSmart company. With an impressive amperage draw of 112.5 amps, this unit can heat up a lot of water, and it even serves as a whole-house unit. With this much power, you could simultaneously run 3-4 showers at once in a middle-to hot climate, but it would be a very good high-demand solution in a hotter climate.

To make the electric tankless water heater work properly, you would at least need a 200-amp service and 3 double poles, 40-amp breakers. The self-modulating technology makes sure that all of that power isn’t used at once unless the situation calls for it. You control the heater via its digital temperature control.

Unlike other manufacturers, this model has a lifetime warranty for its parts, and with proper care and maintenance, users have reported that it can last for years.

Read More: EcoSmart ECO 27

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5. Stiebel Eltron Tempra 12

Stiebel Eltron Tempra 12 223420 Tankless Water Heater

From the lower end of the Tempra series, we have our next point-of-use tankless water heater. The performance of this unit depends more on the climate of the place where it is installed than anything else. If the demand for temperature rise is small, then it can power a standard or low-flow shower.

However, if you are installing this electric tankless water heater somewhere colder, where the water is, let’s say 42-52°F, then you could use it to support a kitchen or bathroom faucet. Point-of-use units like this one can save you money, but you need to be smart about where you will use them.

Speaking from an energy draw perspective, the load that this heater requires isn’t that high – just 50 amps. An electrical service of 100 amps could run it smoothly, but 150 amps would be a bit safer. The warranty on the parts lasts for 3 years, while the anti-leaking warranty lasts for 7 years.

Read More: Stiebel Eltron Tempra 12

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6. Bosch US12 Tronic 3000

Bosch US12 Tronic 3000 Tankless Water Heater

The most budget-friendly electric tankless water heater comes from a world-renowned German company – Bosch. Power-wise, this unit doesn’t put high numbers like some of the other heaters on this list, but it does what the manufacturer says it does. Namely, this is a compact point-of-use tankless heater meant to support a single sink.

Whether the heater is placed at an office, home or small restaurant, this unit can be discreetly installed and will fully support a single faucet. Thanks to quality parts put into this unit, the energy efficiency comes to 98%, meaning you will waste a lot less energy. Users report that if the heater is used properly, it can last years beyond its warranty period.

For most of the parts, the company gives a 1-year limited warranty, except for the heating chamber, which gets a 5-year warranty.

Read More: Bosch US12 Tronic 3000

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Atmor ThermoPro 3.7 GPM Tankless Water Heater
  • Product: Atmor ThermoPro 3.7 GPM
  • 3.8 Customer Rating
  • Price: $$
  • Size (inches): 17.4 x 5.2 x 13.4
  • Weight(pounds): 17
  • kW @ 240V: 18
  • GPM @ 35 F Rise: 3,7
  • Amperage (amps): 75
  • Warranty for Parts(years): 2
Sio Green IR30 POU Tankless Water Heater
  • Product: Sio Green IR30 POU
  • 4.1 Customer Rating
  • Price: $
  • Size (inches): 13.5 x 8.5 x 3
  • Weight(pounds): 5
  • kW @ 240V: 3.4 @ 120V
  • GPM @ 35 F Rise: 0,8
  • Amperage (amps): 28,3
  • Warranty for Parts(years): 2
Stiebel Eltron Tempra Plus 36 kW Tankless Water Heater
  • Product: Stiebel Eltron Tempra Plus 36 kW
  • 4.5 Customer Rating
  • Price: $$$
  • Size (inches): 21.7 x 20.1 x 9.6
  • Weight(pounds): 19
  • kW @ 240V: 36
  • GPM @ 35 F Rise: 7,03
  • Amperage (amps): 150
  • Warranty for Parts(years): 3
Titan SCR2 N-120 Tankless Water Heater
  • Product: Titan SCR2 N-120
  • 4.0 Customer Rating
  • Price: $
  • Size (inches): 7 x 10 x 2.75
  • Weight(pounds): 8
  • kW @ 240V: 11,8
  • GPM @ 35 F Rise: 2,5
  • Amperage (amps): 54
  • Warranty for Parts(years): 1
Marey ECO150 Tankless Water Heater
  • Product: Marey ECO150
  • 4.8 Customer Rating
  • Price: $
  • Size (inches): 8.7 x 3.5 x 14.2
  • Weight(pounds): 10,1
  • kW @ 240V: 14,6
  • GPM @ 35 F Rise: 3
  • Amperage (amps): 70
  • Warranty for Parts(years): 5
Stiebel Eltron DHC 3-1 074050 Tankless Water Heater
  • Product: Stiebel Eltron DHC 3-1 074050
  • 3.9 Customer Rating
  • Price: $
  • Size (inches): 14.18 x 4.12 x 7.87
  • Weight(pounds): 4,6
  • kW @ 240V: 3 @ 120V
  • GPM @ 35 F Rise: 0,46
  • Amperage (amps): 25
  • Warranty for Parts(years): 3

7. Atmor ThermoPro 18 KW

Atmor ThermoPro 3.7 GPM Tankless Water Heater

While our next unit does have a very simplistic design, don’t think that it’s weak, because there are some quality heating elements under the hood. Thanks to the 18-kW consumption rate, this machine has a 75-amp draw. To properly cover it, you will need 3 single-phase double pole breakers at 30 amps each.

Providing your shower with enough hot water can even be achieved in cold climate areas where the water is 37°F with this unit. Of course, if the temperature is higher, then you could support up to two standard showers with this heater.

Like many on our list, this model also has self-modulating technology built-in, so the machine will not waste energy while gradually heating up the water. All of the parts are covered by a 2-year limited warranty but the manufacturer also gives a 7-year warranty against leakage.

Read More: Atmor ThermoPro 18 KW

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8. Sio Green IR30 POU

Sio Green IR30 POU Tankless Water Heater

Electric tankless water heaters are, by no means, new technology, but our next model is a bit different than the rest on our list. Instead of using classic copper or aluminum heating elements, this tankless water heater uses quartz-based heating tubes. Also, a special coating is applied to the quartz tube, so that it can be heated by infrared energy.

The result of this combination is a compact point-of-use water heater that can supply hot water for a single faucet as the wattage for this unit is just 3.4 kW at 120V. You can use it in an RV, boat, outdoor kitchen sink, and more. While the parts are more recyclable and the energy is greener, this unit can only operate in areas where the inlet water temperature is 62°F and above.

Parts for this unit are covered by a 2-year limited warranty.

Read More: Sio Green IR30 POU

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9. Stiebel Eltron Tempra Plus 36 KW

Stiebel Eltron Tempra Plus 36 kW Tankless Water Heater

We’ve seen an example or two of electric on-demand water heaters that can provide multiple fixtures with hot water, but this unit is on a higher level. This is the largest capacity tankless water heater from the Tempra Plus series.

In a warm climate of around 70°F, this unit produces up to 7.5 GPM of hot water, which is enough for 4 simultaneous low-flow shower heads, and a faucet or two. With such a high flow rate, this could easily be a whole-house solution in many situations, even in colder climates, depending on the size of your home.

With great flow, there is usually a great power draw as well. In order for this model to be able to give this level of performance, it has a minimum amp draw of 150 amps. You also need an electric service of 300 amps to support it and, at the very least, 3 dual-pole 50-amp breakers. The warranty for this unit comes in the form of 3 years for parts and 7 years for leaking.

As an added safety feature, there is an anti-scald setting for this unit which you can adjust from 140°F to 109°F.

Read More: Stiebel Eltron Tempra Plus 36 KW

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10. Titan SCR2 N-120

Titan SCR2 N-120 Tankless Water Heater

Here we have another model that shines the most in a warmer climate. As a smaller on-demand electric water heater, it can cover 1-2 bathrooms if the groundwater being used is 65°F. The manufacturer recommends this model for warmer climates as well.

To adjust the temperature, you need to use the front panel, however, it doesn’t have a temperature gauge with numbers. Given the relatively small size of this unit, it can easily be used in a mobile home, boat or kitchen.

You won’t have much to worry about regarding amp draw with this unit as it tops out at 54 amps. Also, it only uses 11.8 kW while operating. A single 60-amp double-pole breaker would be the minimum requirement for this heater to work properly.

Electrical parts are covered by a 1-year limited warranty, but the water carrying components actually have a 10-year warranty period.

Read More: Titan SCR2 N-120

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11. Marey ECO150

Marey ECO150 Tankless Water Heater

The first thing you will notice about our next model is the water drop styled LCD panel which you can use to control the unit. The casing itself is fairly small and only weighs 10.1 lbs, so you can mount the heater at just about any location.

Smaller point-of-use units like this one tend to be very useful in warmer areas where the groundwater exceeds 68°F. With a lower temperature rise, this electric on-demand water heater could support up to 2 low-flow shower heads and another fixture. The heating element inside of this particular heater was designed in Germany, and the power it draws comes to 14.6 kW.

For proper use, it is recommended that the machine is hooked up to at least a 70-amp double-pole breaker. Also, the manufacturer suggests that the water heater should be placed no more than 40 feet away from its point of use. All parts are covered by a 5-year limited warranty.

Read More: Marey ECO150

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12. Stiebel Eltron DHC 3-1

Stiebel Eltron DHC 3-1 074050 Tankless Water Heater

The last model on our list also has the lowest power draw out of all of them. Coming in at 3 kW, the only application this water heater can support is for a single sink. For optimal results, the manufacturer recommends that their unit should be used in a warmer climate.

Even so, the best you can expect from this unit is at 0.5 GPM, which can support a low-flow bathroom faucet. The copper heating coil provides a longer lifespan for this machine. To prevent any injury, the water heater comes with a scald-guard so that the water stays within safe limits.

A single 25-amp breaker is needed to use this electric tankless water heater. The parts of this unit are covered by a 3-year warranty, and a 7-year warranty for leakage.

Read More: Stiebel Eltron DHC 3-1

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Terms to be Known

Here is a short list of terms you need to be aware of, before you can fully understand the information we are providing you.

  • GPM/Flow Rate

The GPM (Gallons Per Minute) rate shows how much water will flow through a fixture or appliance in 1 minute. It is also known as the flow rate of the tankless water heaters. The larger the flow rate, the more water output, and pressure you can have. Better flow rate also means that a single unit can support multiple showers and faucets.

  • Temperature rise

This represents the total number of degrees that a tankless water heater can heat up. Naturally, water temperature is colder in harsher climates, so water heaters have to heat it up more if they need to achieve an optimal temperature.

  • Maximum kW

Represents the maximum number of kilowatts (kW) used per hour by any appliance.

  • BTU

Stands for British Thermal Unit. We use this unit of measure heat in general, and to determine how much energy is needed to heat up 1 pound of water by 1°F. This is also the measure of unit’s cooling/heating power.

  • Amps

Represents how much electric energy can flow through circuit breakers, wires, appliances and so on.

  • AWG

This acronym stands for American Wire Gauge and represents the different, standardized sizes of wires necessary for a safe use of any machine or appliance.

Tankless vs Tank Water Heaters

Tankless vs Tank Water Heaters ReviewWater heaters with tanks have been around for a long time. While they presented a very practical solution when they were invented, they aren’t the most advanced or practical solution now. In this section, we will go over a few important differences between tankless boilers and tank water heaters.

1. How Much Hot Water Can You Really Have?

One of the greatest limitations of tank water heaters is actually their tank. It’s limited by how much water it can store. People are often faced with the issue of not having enough water after someone else had finished their shower. This is especially a huge problem in the mornings when you are in a hurry. Also, if the water is being used all day by regular showers or washing clothes or dishes, this will again drain your supply of hot water. There’s nothing worse than waiting around for the water to heat up, or changing your schedule because of it.

On the other hand, a tankless water heater provides a continuous flow of hot water when you need it. This is why they are often called on-demand water heaters, or instantaneous water heaters. In fact, as long as you have power or gas, you can have an endless supply of hot water if you use a tankless water heater.

2. Where Can You Install an Electric Tankless Water Heater?

Electric Tankless Water Heater ReviewsA water heater that uses a tank often proves to be a logistic problem as well. The larger capacity that a tank has, the more space it will take up. Because of this, you have to store it in a garage, or you have to find another creative solution just to have hot water in your home. Also, water heaters have a distance limitation – it’s best to put them near the output source, but this limitation differs from unit to unit. Generally, smaller units need to be put really close to the water output source – a shower or a faucet. Larger units have the pressure output that can withstand longer distance from the source (usually, it’s the basement).

A typical 60-gallon water heater might take up 72 cubic feet of volume, while various tankless water heaters that provide an endless stream of water can take up as little as 2 cubic feet of space. However, 60 gallons isn’t even enough to cover the needs of a family of 4. Because of the compact design that most tankless heaters have, they can be installed just about anywhere – even outside the house.

3. Cost Efficiency

While it is true that water heaters with tanks are the cheaper option when you buy them, they are not as energy efficient as tankless water heaters. The reason for this is because the main job of a tank water heater is to always have a full tank of water set at a specific temperature. This means that they will constantly waste energy on reheating the tank – even when you are not using the water throughout the day.

Once the hot water is spent, it will refill itself and heat the water again. Even if you aren’t using any hot water in the house, by continuing to heat the water, the unit just adds expenses to your bill. The advantage of tankless water heaters is that they will spend energy only when they are in use.

4. Do you like a big power bill?

Because of the continuous drain on your gas or electricity, a tank water heater will be responsible for the higher bill at the end of the month, as opposed to the tankless water heater. Manufacturers have made tankless water heaters that can save anywhere from 20% to 50% on your utility bill thanks to the superior technology.

5. How long will it last?

A typical tank water heater has a warranty period or a working lifespan of 10-15 years – if you are lucky. Most people claim that their tank water heaters last around 5 years. If a tankless water heater is installed and maintained properly, their lifespan is 2 or 3 times greater than that of a standard water heater. Manufacturers are so confident in the lifespan of these machines that they even give lifetime warranties on them.

6. The health of the unit

Water sometimes has a higher mineral content (also known as the hard water), and this makes many tank water heaters have a shorter lifespan. Because tanks are always filled with water, they need to be periodically drained and cleaned, depending on the water that is being used. If owners don’t do this, it can ruin the parts inside the machine, which will require costly replacements.

Tankless water heaters come with technology to prevent “scales”, or hard water residue from building up inside of them. Because of this, most tankless units only require annual maintenance and servicing.

7. Installation

Tankless Water Heater InstallationThe initial cost of a tank water heater and its installation are indeed cheaper than that of a tankless water heater, but that isn’t the whole picture. In order to understand the final cost of going with the cheaper option, you must also consider some facts. For example, you need to know that you will be paying more for energy bills, plumber maintenance fees but still – you will get the machine that has a short lifespan.

A tankless water heater installation does cost more when you are remodeling, but if it is a new home, the costs are virtually the same. Because of the much longer lifespan of these water heaters, the slight price advantage that tank water heaters bring in the start is negligible.

All in all, it is precisely because of the technology, longevity, and efficiency of a tankless water heater that you can make up the money in energy savings. Basically, you can negate the higher initial price and even end up saving money. A tankless water heater is a long-time investment for your home and it will pay out in the long run.

As the old proverb goes – a wealthy man once said: “I am not rich enough to buy cheap things”, or in simple terms – you get what you pay for.

Tankless Water Heater Types

Here we will discuss the main types of tankless water heaters, including their main points and their differences. There are two types – the electric tankless water heater, and the gas one.

1. Electric Tankless Water Heaters

An electric water heater is a compact machine used for efficiently heating up running water on demand. They come in a variety of sizes and applications. To get the most out of the savings that these machines can provide, it is recommended to install them in the rooms where you will use hot water. Because of the small storage space they require, this is an easy feat to accomplish.

Since they do not require ventilation, they are safe to install anywhere in your home. These so-called point-of-use water heaters are practical solutions for something the kitchen sinks, or larger units that provide hot water for the entire bathroom.

Their sizes are categorized by the max kW they consume while working, whereas the maximum is 36kW for residential use. A 28/32kW on-demand water heater can handle from 2.5 to 3.5 bathrooms at once, depending on the use. For a whole-house solution, it is generally recommended to get more than one tankless model for your home.

2. Gas Tankless Water Heaters

The second type of tankless water heaters is powered by either natural or a propane gas. These machines do not differ greatly when it comes to their mode of operation or efficiency. However, the installation process for gas models is a bit different since they require electricity for their pilot light and a gas connection for their fuel source.

The water heating process is the same as it is in an electrically powered unit, except there is an additional step – the gas is burned in a chamber, which creates the heating energy. Then, this heat is transferred to the heating elements and pipes. There is also the ventilation process of getting rid of harmful gas fumes that simultaneously happens when the water is heated.

If you want to get more detailed information about these machines, you can find useful materials online and read informative buying guides for gas tankless water heaters.

2.1 Natural Gas Tankless Water Heaters

When choosing a water heater system for your home, it is important to consider a few factors, like climate for example. We will go into more detail about this later, but for now, it’s enough to say that in cold areas, natural gas-powered heaters are more efficient than the electric ones.

Natural gas models have a high water-flow capacity and great heating ability. Because of these factors, natural gas tankless water heaters are often used as a whole-house solution.

2.2 Propane Tankless Water Heaters

Propane Tankless Water HeaterWhat is true about natural gas on-demand water heaters can also be said about propane-powered units. They work well in cold areas, they have a great heating ability and high water-flow capacity.

The main advantage of a propane system is the fact that it’s accessible where other heating systems fail. If you live in a rural area where you can’t have a dedicated gas line, you can buy a propane tank and hook it up as your energy source to have a whole-house water heating solution.

How Does an Electric Tankless Water Heater Work?

An electric tankless water heater functions based on the same principle just like a regular tank water heater, but it’s much more effective. Instead of a tank, these machines use powerful electric heating elements inside of small water pipes or chambers. The set-up can be with 1, 2 or even 4 chambers, depending on the model.

Every chamber has a heating element and a thermistor, or possibly just one thermistor that detects the overall water temperature in the unit. You will always need to program the desired temperature for an electric tankless unit, and once you turn on a tap or a shower, the water will go into the machine and the thermistor will start the heating process.

The next step differs between manufacturers. Some electric on-demand heaters will start a heating element at its maximum amp output and heat the water up. If the element has a max of 30 amps, that means that once the heating element is turned on, you will get a 30-amp power spike at your circuit breaker.

Best Tankless Water HeaterThis can cause your lights to flicker for a moment because of the sudden demand for power. Don’t worry, if it’s hooked up the right way, it should go away in a matter of seconds. Because these elements go from 0 to 100% power, we call them non-modulating.

Once the element becomes too hot, it will automatically shut down. When the temperature of the water goes down, the element gets switched on again, and it bounces like that between ON and OFF setting. If one electric heating element isn’t enough, then the next one will be used as well.

The slight issue with these models is that with all the sudden high amp demands, it is going to run up your electric bill in prolonged use. This cost is still less than tanked water heaters rack up because they work non-stop, however it’s still less cost-effective than other types of electric heating elements. Other electric heating elements can be programmed to bring up the power slowly, thus making a lesser electric power drain and a more cost-effective heating process.

By raising the electric power consumption gradually to achieve the desired temperature level, you won’t use more power than you need, and you won’t get flickering lights or circuit breaker problems. Units with this technology are called ‘self-modulating’ and they are the most efficient models when it comes to electric energy consumption.

Electric Tankless Water Heater Buying Guide

When choosing an electric water heater for yourself, there are several characteristics that can and will influence the choice you need to make. In our buying guide, we will cover the most important characteristics that will determine the specifications needed for meeting your water heating needs.

This list of characteristics has been carefully put together for your benefit. You will need to balance not just one, but all of these characteristics in order to make an informed decision. This way you can get the most out of the savings from these water heaters.

1. Efficiency

The U.S. Department of Energy has determined that the second largest utility cost in an average home is hot water. Electric tankless water heaters are so efficient that they have an EF rating of up to 99%. The energy factor (EF) of all water heaters determines how efficiently every unit of consumed energy is used to heat up the water during typical use.

While the EF rating may vary, electric on-demand heaters don’t drop under 90% efficiency. The factors that determine this are recovery efficiency, cycling losses, and distance from point of use.

Recovery efficiency represents how well the heat is transferred from the energy source to the water. The heating elements used by electric tankless units are usually made from various metals. Casting aluminum delivers the highest heat efficiency, while copper has the lowest (90%).

Cycling losses, in this case, represent the heat that is lost when water circulates from inlet or outlet pipes. Because most pipes are designed to transfer water efficiently, their installation is the leading cause of heat loss.

The most important thing you need to remember is to use a pipe with a rubber gasket so that it forms a perfect seal. Also, when placing the pipe, even though some manufacturers say it is not needed, apply the sealant tape or a paste to absolutely prevent leaks and heat loss.

How far the water must travel from the unit to your fixture also plays a vital role in the efficiency of your heating system. The compact design of electric tankless water heaters allows them to be installed virtually anywhere with a water and electric supply. By being close to the point of use, any heat loss from the hot water becomes negligible, if there is any at all.

Because electric on-demand units are placed near the source of use and use efficient heating elements to heat up water in small spaces, it becomes clear why they have a high EF rating. Most manufacturers will state the efficiency of the model in the manual, or in the rest of the supplied literature that comes with them.

2. Size

As with all appliances in your home, size really does matter. The size of your unit needs to be determined by the job you want the machine to accomplish and where you can put it. The two main application categories for electric tankless water heaters are point-of-use and whole-house.

Point-of-use models, as the name implies, are meant to be used near the fixtures which will use the hot water. Given their compact design, placing them won’t be an issue, but you have to keep in mind that point-of-use units generally have a lower max kW, meaning they are limited by how much hot water GPM rate they can produce.

The size of point-of-use heaters can be so small that they will fit right under your kitchen sink, or as big enough to fit inside of a small closet if you want to make it more discrete.

Whole-house models are slightly bulkier, but they also have more power. These machines are built to withstand the needs of an entire household, covering multiple bathrooms and fixtures. Of course, these units require more power, and additional breakers will have to be used in your service panel to support the heater.

When choosing the size of your new unit, you have to remember that more power means the machine can have a higher flow rate (GPM). If the machine isn’t big enough, you will still have hot water, but the volume of the water flow rate will drastically go down. This could mean a cold surprise for you in the shower if other fixtures are turned on at the same time, and your tankless water heater can’t handle the load.

A good way to calculate how big your tankless water heater needs to be is to calculate the GPM flow rate of all the fixtures that it needs to support. This will show you how powerful the heater should be.

3. Electrical Infrastructure

Electrical InfrastructureThe electrical infrastructure is very important for your home because of various safety reasons. Before you buy an electric tankless water heater, you need to consider the electric load your infrastructure needs to support. That way the water heating and the rest of the power consumers can all work properly, at the same time.

3.1 Wiring System

You have to make sure that the wiring in your home is up to code, which should go without saying. Next, there should be enough room, as well as the right type of service panel to accommodate the new heater. Replacing the service panel and additional wiring could be a major expense, so you may end up choosing a less powerful electric tankless water heater.

If you want to safely run an electric on-demand water heater, most manufacturers recommend having a standard 200-amp electrical service at 208-240V. This is enough to support a whole-house model under normal everyday use. Remember, even though these machines are energy efficient because they work on demand, their energy needs still can be substantial.

This is why on-demand heaters require thicker wiring, like a 6, 8 or even 10 AWG wires. They also need something better than 30-amp double-pole breakers as they either won’t work at 30 amps or will underperform and cause problems for the rest of the house. If you haven’t handled them before, you can read up on circuit breakers here, or possibly hire an electrician to help you.

Because of the high amperage these machines need, an old house that doesn’t have an up-to-date service panel may not be able to support an electric tankless water heater. But, some smaller point-of-use models can work on an electrical service of 100, 125, or 150 AMPs.

3.2 Service Panel Utilization

Another important tip: people tend to misunderstand what their service panel can support. If you count the breakers you already have and when you reach the 200 amps mark, you might think ‘well I can’t add anything to this system’ – but, you would be wrong. There is a diversity factor in play here that you need to be aware of.

Simply put, the diversity factor states that under normal circumstances you won’t be running all of the appliances from all of your power outlets in your home, at the same time. If you have a 200-amp service panel, normally you are using a fraction of that, with ups and downs during the whole day. So, you can easily swap out your 30-amp breakers for 70- or 80-amp breakers to fit the needs of your heater.

You only need to make sure that while your electric on-demand heater is running, you don’t turn on so many other appliances and reach the limit of your electrical service. To avoid overloading your service panel, check to see if the water heater can be supported by your panel and that you have the right breakers for it.

If you aren’t sure what your electrical service can support, you can always hire a professional electrician to check out your setup.

4. Warranty

Because of the simplicity of their design, electric tankless water heaters tend to last a long time. This is why their warranty period can last from a few years (if it’s a smaller model) to a lifetime. The terms of warranty policies can differ from manufacturer to manufacturer. In general, if a machine has a lifetime warranty on its parts, the manufacturer will insist that the unit is installed by an approved and licensed professional.

5. Climate

The final characteristic that we need to talk about isn’t about the water heater per se, but about where you live. Yes, climate does influence the performance of your on-demand heater to an important degree. Why? Because the temperature of the ground and the water coming from it into your home also define how strong your electric tankless water heater needs to be.

Temperature rise dictates by how much your water heater can raise the temperature of the water coming from the pipes outside of your home. If you live in a place with a warm climate, where the weather is around 90°F (32°C) then you only need a temperature rise of 30°F to get the average hot water temperature of 110°F (43°C).

That is an easily achievable goal, but the colder the climate, the more work your machine will have to do to get the water hot enough. If you live somewhere that requires a 50, 60 or even a 70°F rise in temperature, then your choice of units is going to become very limited and costly. This is because more powerful models simply cost more, and you would need them for a drastic difference in water temperature.

Salesmen who are simply out to make a quick buck may leave out this vital piece of information. But we know that climate plays a too important of a role when choosing an electric on-demand water heater, so be careful. We wouldn’t want you to pay for an expensive machine that couldn’t even provide you with a hot shower.

How to Install an Electric Tankless Water Heater

Install an Electric Tankless Water HeaterInstalling an electric tankless water heater is fairly simple, but some warranty policies do require an authorized licensed professional to do it. While the installation process may differ slightly between models, we will provide a general installation guide that will work for most units.

Step 1 – After unboxing your heater, you need to prepare the area where you are going to mount the unit. Measure out the length between the inlet and outlet connector on the device. Set up your water pipes according to the height where you plan to mount your unit. Always make sure that when you’re doing plumbing work, you shut off the water valve.

Step 2 – Unscrew and remove the front panel of the heater. Depending on the model, your heater may need to be mounted on the wall by a separate or onboard mounting bracket. Usually, 4 screws are needed for the job. Makes sure the unit is leveled and securely fastened to the wall.

Step 3 – Connect the cold-water pipe to the inlet connector, and hot-water pipe to the outlet connector. Remember to use a sealant tape or paste on these connectors to ensure a tighter seal. Every unit has a maximum pressure (PSI) that it can withstand. If the pressure that’s coming from the water pipes is greater than the heater can handle, a pressure release valve will also need to be installed.

Step 4 – Once they are connected, turn on the water and faucets, or other fixtures, for about 2-3 minutes. This will drive out any remaining air in the chambers. This is a very important step and must be performed, otherwise, you risk permanent damage to the heating elements.

Step 5 – Carefully inspect all the connections for leaks once you have turned on the water.

Step 6 – Make sure that the power is turned off at the circuit breaker, then run the appropriate gauge wire from each breaker to the tankless water heater. The number of wires and breakers that are needed vary from one model to another. Remember that every incoming circuit also requires a ground wire as well.

Step 7 – To make sure that there are no mix-ups with the multiple wires for the breakers, use colored insulation tape to label the wires that go on the same breaker. Double check that you have used the correct breakers and wire gauges for the machine. Also, before turning on the power, make sure you have purged the unit from any air that was in the water chambers or pipes.

Step 8 – Once you have checked everything, you can switch your new electric tankless water heater.

Maintenance of Electric Tankless Water Heaters

Maintenance of Electric Tankless Water HeatersThanks to the simple and effective technology used in electric tankless water heaters, there isn’t a lot of maintenance involved.  The main thing that will determine how often your model will need maintenance is the hardness of your water. The greater the number of minerals in your water, the more often you are going to need to clean out the heating elements in your machine.

Some units will require you to remove the electric heating elements from the heating chambers and clean them with white vinegar, or you will simply need to flush the entire system with it. Other models require cleaning the aerator of the faucet, as well as the filter screen and showers heads.

The mineral build-up at these locations could slow down your hot water flow, which is one of the signs that some maintenance is overdue. Here is a simple video that demonstrates how easy it is to clean the filter that is used by the water heater.

If you are flushing your system with white vinegar or removing the electric heating elements manually, here are a few simple rules to follow.

Turn off the power and water supply, and lock the breakers before doing any maintenance work. Do not, under any circumstances, start servicing your unit while the power or water service is on, as this can damage your unit or possibly hurt you.

Please consult your manual to see the diagrams of how your unit is assembled, and how to properly disassemble it. First, you should remove the electrical wires connected to the heating elements, then the electrical element itself. To clean it efficiently, simply submerge the coil into undiluted white vinegar, and after wiping them clean, put everything back the way it was.

When flushing out your system with white vinegar, it is a good idea to have purge valves installed as this will make it easier for you to flush out the system. Make sure that all of the hoses you attach are sealed properly so that you can prevent leakage. By using these valves, you will be able to bypass the normal water line with additional hoses, and with a pump, you can easily make the vinegar circulate throughout the system.

There is an easy to follow instruction video below on how to do it hassle-free. Once you are done, do not simply turn everything back on – first make sure you have flushed the vinegar and any scale or mineral residue out of the system.

On average, these units will need some maintenance every 12-18 months depending on the water you use and a tankless water heater is also easy to repair.

FAQ’s About Electric Tankless Water Heaters

In this section, we will try to cover the common concerns people have about electric tankless water heaters, and we will provide accurate responses.

1. Will an electric tankless water heater be compatible with my kitchen sink and dishwasher?

Yes. These machines specifically shine as point-of-use appliances and will work well with dishwashers and sinks simultaneously. Keep in mind that most modern dishwashers already come with a heating element inside of them.

2. Could an electric on-demand water heater work for an in-floor heating system?

Probably. There are units that could absolutely cover the needs of an in-floor heating system. But you will need to check how much water flow and temperature rise would be needed to cover the needs of such a system so that you can choose the right heater.

3. Can an electric tankless water heater work in a trailer, RV or mobile home?

Because of their lightweight and compact design, electric tankless water heaters can be easily put into some type of mobile home or trailer. You just need to be careful and select the unit with just the right number of amps that your mobile home could cover.

4. How to prevent water leaks from the inlet/outlet connectors?

How to Prevent Water Leaks From the inlet-outlet ConnectorsSince the leaks directly influence the efficiency of your machine and the bill you will get, you need to make sure the connectors aren’t allowing any water to get out. You can accomplish this by using water pipes with rubber gaskets that can help in making a tighter seal. Also, you can use a sealant tape on the connector itself to make it even tighter.

5. Can electric on-demand water heaters use the well water?

Short answer: it depends. Like we said, climate and water temperature do play an important role. If you live in a cold part of the country, and the water temperature needs to rise for more than 60-80°F, that could be an issue. However, if you are using an electric tankless water heater for small jobs without a large water flow, then it could work.

In a warm climate, the well water shouldn’t be an issue.

6. How much noise is there when the tankless water heater is being used?

As there are generally no moving parts per se in an electric on-demand water heater, there should be relatively little to no noise coming from it. This makes it practical for installing just about anywhere in your home. If it does start making some noise, then there might be something wrong with the unit.

7. Is there anything else I can do to further increase the savings from these machines?

Yes. Older faucets, shower heads, and other fixtures tend to have a higher GPM water flow rate, and they waste a lot of water. To gain the most out of your tankless water heater, replace all of your fixtures with new low-flow ones. They will still get the job done, but your water and electric bill will go down even further.

8. Is the casing water-proof?

Short answer: probably not. Most manufacturers warn consumers to keep the machine away from direct contact with water. Some could be more water-proof than others, but you need to consult the instruction manual for that. Better to be safe than sorry and simply install the unit where it can’t get wet.

kW @ 240VGPM @ 35 F RiseAmperage
Warranty for parts
EcoSmart ECO 1111.5 x 8 x 3.757132.5457Lifetime
Stiebel Eltron Tempra 24 Plus 22419921.7 x 20.1 x 9.616.1244.681003
Rheem RTEX-134 x 9 x 137132.54541
EcoSmart ECO 2717 x 17 x 3.514275.27112.5Lifetime
Stiebel Eltron Tempra 12 22342019.5 x 21.5 x 8.513.5122.34503
Bosch US12 Tronic 300012.2 x 3 x 6.56122.3501
Atmor ThermoPro 3.7 GPM17.4 x 5.2 x 13.417183.7752
Sio Green IR30 POU13.5 x 8.5 x 353.4 @ 120V0.828.32
Stiebel Eltron Tempra Plus 36 kW21.7 x 20.1 x 9.619367.031503
Titan SCR2 N-1207 x 10 x 2.75811.82.5541
Marey ECO1508.7 x 3.5 x
Stiebel Eltron DHC 3-1 07405014.18 x 4.12 x 7.874.63 @ 120V0.46253

Wrap Up

We’ve supplied you with electric tankless water heater reviews as well as an informative buying guide. From our in-depth research you can see that, while finding a good on-demand water heater may not be the simplest task, it isn’t impossible either.

Be sure to read all of the suggestions when you are making your decision. Also, always take a few days to reach your decision, as impulse buying with this type of equipment could be very costly in the long run.

Since this technology is already popular in Asia and Europe, it is no wonder that it is steadily spreading throughout North America. It is our sincere hope that you will use this data to make an informed decision when you look for the best electric tankless water heater for yourself.