Best Tankless Water Heater Reviews (Choose the Best in 2021)

Disclaimer: is supported by its audience. When you purchase through links on our site, we may earn a small commission at no extra cost to you.

There are dozens of tankless water heater brands today. Americans are buying the water heaters in large numbers thanks to the fact that they provide hot water whenever you need it, they are more durable and more energy efficient. But while they certainly are a worthwhile investment, it is important that you do due diligence to get the best tankless water heater for your home. Without proper research, you may undersize your home or pay too much for a heater that is not worth it. Fortunately, we are about to go through everything you need to know about these heaters. Read on for our tankless water heater reviews for more information.

Keep in mind that the following six heaters are best-selling in various online retail stores. All you need to do is compare them in terms of features and water heating capabilities, and you will probably spot one to fulfill your home’s water heating needs.

Top 6 Tankless Water Heaters

Tankless Water Heaters Reviewed

EcoSmart ECO 18 Electric Tankless Water Heater

best tankless water heaterThe ECO 18 model is EcoSmart’s best-selling tankless water heater. It is also one of the best rated tankless water heaters on the market today, thanks to its durability, energy efficiency, and ability to deliver hot water in climates with temperatures 62 degrees and above.

The construction of this whole house tankless water heater is made of durable metal components, such as copper and stainless. So you can expect it to deliver reliable performance for years. The product is also backed by the manufacturer’s lifetime warranty, which speaks to the quality of this tankless water heater.

It offers the capacity to heat up to 2.5 gallons per minute. This is the amount that a standard shower head produces. However, if you have a water saving shower head, the device can produce enough hot water for both the shower head and a faucet. So, as you can see, it’s one of the lower flow units, which makes it a better choice for smaller households.

This is also one of the most energy efficient tankless water heater. It features self modulating technology, which adjusts the amount of energy used based on how much hot water needs to be produced. So the device doesn’t use more energy than required and this can help you save up to 50% on your water heating costs.

On the front of the unit, you can also find a temperature control knob. It allows you to adjust the temperature level in one degree increments between 80 and 140 degrees Fahrenheit.

As it is an electric tankless water heater, the installation is less complicated compared to gas units. It doesn’t require any costly ductwork or gas lines. However, it will require some basic plumbing, proper wiring, and two 40 amp breakers.

Another advantage of this electric on demand water heater is its compact design. It is small in size and weighs just 11.25 pounds, so this heater will fit almost anywhere, even in a tiny utility closet.


  • 18,000 watts.
  • Delivers 2.5 GPM.
  • Digital temperature control.
  • Self modulating technology.
  • Durable components.
  • No vent installation.
  • CSA/UL certified.
  • Inexpensive.
  • Lifetime warranty.
  • If you do the installation yourself, it will void the warranty.
  • Lifetime warranty is applicable only for residential use.
  • Takes about 30 seconds for the hot water to hit the faucet or shower.

EcoSmart ECO 11 On Demand Hot Water Heater

tankless water heater reviewsECO 11 is another great unit from EcoSmart and it’s the perfect choice for those that are looking for a budget tankless water heater. However, keep in mind that the lower cost comes at the price of lower output capacity.

It can deliver a maximum of 2 GPM, so it’s better suited for low flow applications. You could maximum use it for one shower head and one faucet. And keep in mind that in colder climates or where the incoming water temperature is below 67 degrees Fahrenheit, the output would be even lower.

Similar to ECO 18, this tankless water heater features digital temperature control. The unit is equipped with a dial that allows you to set the preferred temperature. Moreover, the adjustment is done in one degree increments, so you get precise temperature control.

Another similar feature is the self modulating technology, so the water heater automatically regulates the amount of energy used. This technology in combination with the tankless design results in reduced water heating costs up to 50%.

This is also a 13,000 watt appliance. For the installation, it requires a 125 amp electrical panel and one 60 amp breaker. On top of that, it requires proper wiring and plumbing. However, since it’s an electric tankless water heater, it doesn’t need any duct work.

This is also a small tankless water heater. At 6.5 pounds, it’s almost half the weight of the ECO 18 model. So in all, this unit is a good choice for those that have a lower budget and those who are looking for the smallest, low flow tankless water heater.


  • 13,000 watts.
  • Max 2 GPM.
  • Temperature adjustment in 1-degree increments.
  • Weighs just 6.5 lbs.
  • Budget price.
  • Lifetime warranty.
  • Non-professional installation voids warranty.
  • Low flow.

Stiebel Eltron Tempra 29 Plus High Efficiency Tankless Water Heater

most energy efficient tankless water heaterStiebel Eltron 239223 is one of the best on demand water heaters for bigger households. Depending on the incoming water temperature, this top of the line tankless water heater can deliver up to 4.5 gallons per minute, which is enough to supply hot water to multiple fixtures around the house.

This is an electric instant hot water heater, so there are no vents or fumes to worry about. It also means that you can install it almost anywhere you want, without the trouble of having to meet venting space requirements.

The water heater does require a 240V electric service and it reaches a maximum power draw of 28,800 watts or 120 amps. So it will require a minimum of 200 amps in household electric service and 3 separate 40 amp breakers for the system.

Designed to be more energy efficient, this on demand water heater has an Energy Factor of 0.99 and it features intelligent self modulating technology. It ensures continuous energy savings with no standby losses.

The system also features Advanced Flow Control technology, which ensures that the water maintains the chosen temperature. It works by automatically adjusting the water flow in order to keep the water hot.

This device is also equipped with a digital display. It shows flow rate and temperature. It is also designed with a control panel that allows you to adjust the temperature and use pre-set buttons for temperature memory.

One more benefit of this tankless water heater system is its completely silent operation. It has no mechanical switches, so it stays totally silent while heating up the water, making it one of the quietest tankless water heaters.

However, one of the features of this unit might be a downside for some users. Its working pressure is 150 to 300 PSI. If you have low water pressure, this system might not work for you.


  • 28,800 watts.
  • Delivers up to 4.5 GPM.
  • Digital display.
  • Temperature memory.
  • Intelligent self modulating technology.
  • Advanced flow control.
  • Silent operation.
  • ANSI/UL certified.
  • 3 year warranty.
  • Takes 10 seconds for the hot water to come.
  • Requires a minimum of 0.77 GPM and 150 PSI for activation.

Rinnai V75IN Natural Gas Tankless Water Heater

best natural gas tankless water heaterIf you’re looking for a good gas tankless water heater, we recommend checking out the Rinnai V75IN model. It offers everything you need in a high quality tankless water heater, including high efficiency, reliable performance, and durability.

This unit has an impressive output of 180,000 BTUs and it can deliver a continuous flow of up to 7.5 gallons per minute, which is the highest flow rate among products on this list. This flow rate is high enough to simultaneously supply hot water to multiple bathroom fixtures and appliances. And this is the highest GPM tankless water heater on our list.

Moreover, if you need even more water flow, this water heater is also available with a flow rate of 9.4 GPM. Except for different flow rate options, this product also allows you to choose whether you would a propane or natural gas powered unit.

This on demand water heater also comes Wi-Fi ready. It offers an optional Control-R Wi-Fi module, which would allow you to monitor the unit’s efficiency and enable voice activation.

As it is a gas powered tankless water heater, its installation requires proper vents and ducts. It does come with an easy to understand manual, but it still might be better to leave the installation in the hands of a certified professional.

The unit also offers different warranty periods for various parts. It’s 180 months for the heat exchanger, 12 months for labor, and 60 months for parts.


  • 180,000 BTUs.
  • Up to 7.5 GPM.
  • Other flow rate options available.
  • Propane/natural gas.
  • Energy Factor 0.82.
  • 98-140 degrees Fahrenheit temperature range.
  • Wi-Fi ready.
  • Ultra Low NOx.
  • Good warranty.
  • Expensive.
  • More complicated installation compared to electrical units.

Rheem RTEX-13 Whole House Tankless Water Heater

good electric tankless water heaterRheem RTEX-13 is also one of the best instant hot water heaters on the market in 2021. This inexpensive unit provides high efficiency and an overall good value for money.

With a flow rate of up to 3.17 GPM, this residential tankless water heater is recommended for smaller to medium sized homes. It provides sufficient output to simultaneously deliver hot water to at least one shower head and one faucet.

This whole house electric tankless water heater also offers the energy saving advantage, so it will allow you to save on your utility bills. Like most other modern instant hot water heaters, this unit also comes with self modulating power control, meaning that it uses energy only on demand. It doesn’t have any energy loss when the device is in standby mode.

Another advantage of this system is the ease of control. It features a dial knob on the front of the unit that you can adjust to get the perfect temperature. It adjusts in one degree increments, so you get very accurate temperature control. There’s also an LED display, so you can view the water temperature.

This is also one of the most reliable tankless water heaters. It uses two copper immersion heating elements that deliver durable performance.

Since this one demand water heater doesn’t use a tank, it’s perfect for smaller spaces. And since it’s electric, it doesn’t require any extra space for venting.


  • 13,000 watts.
  • Up to 3.17 GPM.
  • Self modulating.
  • LED display.
  • Precise temperature adjustment.
  • 5 year warranty.
  • Better suited for single bathroom application.

Stiebel Eltron DHC-E12 Point of Use Water Heater

small residential tankless water heaterStiebel Eltron DHC-E12 is the most popular point of use hot water heater that delivers a maximum of 1.5 gallons per minute. It provides on demand hot water to a single sink or a low flow shower head.

This point of use tankless water heater is also perfect for applications where there’s no high amperage electrical panel available. It draws 50 amps or 12,000 watts, which is lower compared to other units.

For energy efficiency, this residential tankless water heater uses the same self modulating technology. It will reduce your electricity consumption as it makes the heater run when it senses a flow of water.

Moreover, it features an advanced microprocessor that continuously adjusts the flow in order to maintain a constant water temperature output. So you get no temperature fluctuations. And you can set the desired temperature using the simple dial control located on the front of the unit.

This point of use water heater is also tiny, even in comparison to other tankless water heaters. It measures just 4.1″ x 7.9″ x 14.2″, so it can easily fit behind a cabinet or under a sink.


  • Point of use application.
  • Up to 1.5 GPM.
  • Digital temperature control.
  • Self modulating.
  • Smart microprocessor.
  • Electric, so no venting needed.
  • Affordable.
  • 3 year parts warranty.
  • Not suitable for high hot water demand.

What Is a Tankless Water Heater?

A tankless water heater is a heater that provides water on demand. The heaters lack a tank to hold water, meaning that they won’t produce the standby energy losses incurred when you have a tank water heater.

Having no tank, a tankless water heater is a small device. Most of them weigh 70 pounds or less, and they will hardly be larger than your car’s tool box. Perhaps the biggest and most unique benefit of the continuous hot water system is its ability to deliver hot water instantly whenever you need it. Another big advantage of having these heaters is that they are more energy efficient. They don’t produce standby energies, which means that you will never incur such costs. According to the US Department of Energy, you could save in excess of $100 with a gas powered tankless energy water heater. With a tankless electric hot water heater, you could save more than $40 in energy bills every year.


They are small in size and deliver hot water on demand but at a cost. Sometimes ago, the average tankless water heater cost three times a conventional water heater. Today, the prices have evened up and you could find a quality tankless model for less than $500.

How Do Tankless Water Heaters Work?

A typical tankless water heater consists of a gas burner or an electric heating element. When you turn on your home’s cold water tap, water is delivered through the water heater’s pipes into the burner or heating element. The heating elements are often made from copper or other heat conductors so that it is heated instantly and delivered into your shower or sink. With this simple flow, a tankless water heater will always deliver hot water when you need it. There is no waiting for a tank to get filled up.

While tankless water heaters share the same water heating technology, they are not all the same. Some are top rated, some are poorly rated. Some are designed for large homes, some are designed for use in camps. So, what makes tankless water heaters different? It all lies in the technology used to make the heater’s burner or heating element.

Gas powered tankless water heaters extract heat from natural gas or propane. They use a burner that draws heat measured in British Thermal Units. If the heating burner can draw a high number of BTUs per hour, it will perform adequately enough in providing a stable water flow rate. If the heater draws in gas at a low BTU rate, it will most probably deliver hot water at a lower rate.

Electric tankless water heaters don’t vary much either. The heater will be powerful or weak depending on the technology used to make it. Electric water heaters are traditionally also weaker in delivering on demand hot water in large homes. Most of them are also inefficient in cold areas. To overcome this problem, manufacturers install microprocessors or elements that keep the water heater at ideal temperatures to perform.

Tankless Water Heater Advantages

If you find your current tank hot water heater wasteful in energy, you will be impressed by the benefits to expect once you buy a tankless water heater. Basically, expect a tankless water heater to offer everything that your current water heater lacks.

  1. Cost Efficiency

    People will tell you that a tankless water heater is expensive, but they won’t explain the long term cost efficiency you gain with it. Let’s say you invest in a tankless gas powered model at $500. The Department of Energy estimates that you save approximately $100 with a small tankless water heater every year. In five years, you will have saved enough money to upset the initial costs you incurred on the heater. Isn’t that effective? Keep in mind that tankless water heaters can last for 20 or more years. Even with an electric heater, you can save between $30 and $50 every year. In over the 20 years, the heater could serve you and you will have saved a lot of money.

    In addition to helping you save on energy bills, tankless water heaters are easier to maintain. With some models, you simply install the unit and never have to maintain it in any way for the rest of its service life.

  2. Space Saving

    If you have always felt you need some extra space in your garage, a tankless water heater will help you achieve that. With no tank to worry about, you could save a large surface area previously occupied by your conventional water heater. Modern tankless water heaters are so small that you almost don’t have to worry about a place to install them. With the extra space you have in your garage, outdoors or even on a wall, different tankless water heaters can be installed in a variety of places around your home.

  3. Reliability

    Bid goodbye to waiting for a water heater to fill up its tank before you can have a shower. Tankless water heaters supply water on demand. The very best point of use water heaters won’t delay even for half a minute. With one touch of your faucet’s button and you will have enough hot water flowing to help you clean dishes. To have a reliable water heater, you must, however, have the right water heater. We shall help you buy the right heater next. But keep in mind that as long as you have the right quality tankless water heater, you can be certain of its reliability.

  4. Eco friendly

    One of the biggest concerns among people with conventional water heaters is that they are not eco-friendly. Fortunately, manufacturers of tankless water heaters these days ensure that their products are as energy efficient as possible. Most of the top rated tankless water heaters on the market have an energy efficiency rate of between 80% and 95%. Electric heaters are particularly very eco-friendly as they don’t require venting of any kind. Gas powered heaters may be a little bit energy efficient but they are far better off than conventional water heaters.

Best Tankless Water Heater Buying Guide

As we have emphasized throughout this guide, your dream to have a cost effective, on demand hot water heater will only come true if you buy the right one. With a small heater, you will probably never have enough hot water in your shower and sink at the same time. If you buy a very expensive tankless water heater, you will end up feeling like you made the wrong decision. In the next few minutes, read on to view the features and factors that should guide you to buy the right water heater for your home.

1. Gas/Electric/Propane Powered

A hugely important factor to keep in mind as you buy a water heater is its source of power. Most home use tankless water heaters are powered by natural gas, propane, or electricity. Natural gas is the preferred choice for people looking for a high efficiency water heater. Gas water heaters are more powerful than their electric powered counterparts. They also do well in both cold and warm areas.

By contrast, many electric water heaters are only ideal for small families. They are cheaper and most efficient in warm areas. However, modern models feature technologies that make them quite powerful and reliable in both cold and warm areas. Many Takagi models, for example, have microprocessors that help the unit stay efficient even in the coldest of environments.

If you are not comfortable using natural gas for your tankless heater, propane may be a good alternative. Propane gas is easily available at many gas stations. Propane is also durable.

2. Size

Technically, all continuous hot water systems are smaller than conventional water heaters. That means even if you invest in a tankless water heater for large family or home, you will still save space for installation. However, it is important to determine the size of the water heater you want. A small sized heater will be easier to install. Larger, more complicated gas water heaters, on the other hand, ask for more complex installation. Buy a heater that can meet your installation space. If you are looking for a portable heater, look for the lightest.

3. Water Flow

To determine the water flow rate your ideal tankless water heater delivers, add up the flow rate for different fixtures in your home. Showers consume most of the hot water. On average, a high flow shower consumes 2.5 GPM per minute. A faucet consumes 1GPM. If you mostly use these two fixtures the most, then you will need a water heater that can deliver at least 3.5 GPM. If you have a washing machine that you constantly run as you clean the dishes, consider buying a machine with a higher flow rate.

4. Brand

Ecosmart, Ecotemp, and Takagi are some of the most popular brand manufacturers of tankless water heaters. Rheem, Marey, and Rinnai are also popular brand manufacturers. You can choose a product from one of these manufacturers and feel confident in it. However, do more research to learn the benefits that come with buying from each brand. Some have great customer service, while others are good at delivering quality products.

5. Warranty

A warranty gives you the reassurance that you can get your money back if the product fails to meet your expectations.

Tankless Water Heater Installation

Tankless water heaters ask for higher power lines than a conventional heater would. They also in demand for powerful and larger gas supply lines. Also, expect to incur heavily in retrofitting your house to accommodate a gas tankless water heater. With that in mind, consider calling a technician over to handle the work for you if it looks all too complicated. After all, the validity of your warranty will largely be influenced by how well the unit was installed.

Step 1: Turn off your home’s water supply lines

Turn off the water supply from your home’s main source. Disconnect the supply to the old heater too and uninstall it. Note that there is always some water left in the old water lines. Place a bucket underneath the ends of the pipes to collect this water.

Step 2: Place the hardware and all necessary installation accessories for the new heater close to you

Read the unit’s manual to determine where and how you should best install it. Most of the units are designed to be installed on a wall. For electric powered models, this should be easy since no venting is required. For a gas powered unit, install venting. Since it can be expensive and complicated, don’t shy away from asking a technician to help you vent for your gas water heater.

Step 3: Connecting the power source

With venting done and the unit on the wall, connect the cables serving the electrical source. Let the manufacturer’s manual guide you on how to connect each cable. Note that you will need a circuit breaker or two for your water heater. They should be installed next to the heater itself.

Step 4: Run water through the unit

Run water through the water heater and head on to your shower to enjoy.

Tankless Water heater Maintenance

Indoor tankless water heaters rarely develop problems when well maintained. However, once in a while you will experience the heater dropping temperatures or delivering water at a slower rate. If this happens severally, it is time you geared up for some maintenance exercise.

Gas Heater Maintenance

The biggest problem you will experience with a gas heater is the burner getting clogged. When this happens, the water temperatures in your shower will reduce dramatically. To confirm that the burner is really clogged up, you will observe that some of its parts don’t produce flames. Remove it and clean the apertures properly. Return it and check if all apertures burn correctly. If the problem still exists, replace the burner.

Cleaning the water Heater

  1. Turn off the cold water source that leads to your water heater. Turn off the power sources and relief the lines’ pressure by pulling out the silver tab from the pressure relief valve.
  2. You will need vinegar and a bucket for this exercise. In fact, place the sump pump in a bucket containing vinegar.
  3. Connect a hose from the heater’s inlet to the sump pump. Connect another hose from the bucket to the pressure relief valve.
  4. Turn on the pump to scale the water heater. Scaling is the process of removing hard water sediments from the heater.
  5. Remove the inline filter and other filters in the heater and clean them. Replace any worn out filters.
  6. Eject vinegar and replace the bucket with clean water. Turn on the pump and let it run clean water through the system for a few minutes.
  7. Replace the heating elements from your electric model if they are ineffective.

Tankless Water Heater Brands

The first water heater was invented in 1889. As time moved on, technology kicked in and companies began to produce their own water heaters. By the late 1950s, leading water heater manufacturers had already invented tankless water heaters. They were uncommon in the US, but in Europe and Asia, tankless water heaters have been popular for quite many years. Today, the following companies lead in producing respected and quality tankless water heaters.


Rheem is a popular name in the water heater industry. Based in California since 1925, the company has produced some of the best water heaters we have today. As of date, Rheem is also the largest manufacturer of water heaters in the US. Some of its most popular tankless water heaters include Rheem RTGH-95DVLN.


EcoSmart is a popular tankless water heater brand among those who only look for the most energy efficient models. The company advertises itself as making product s that will save you money in energy expenses. The company’s major specialization is in tankless water heaters. According to online reviewers, the company has a great customer service department.


If you love gas powered water heaters, you better go for a Rinnai. The Japanese company has been manufacturing tankless, gas powered water heaters for almost 100 years. The company has several best-selling products such as Rinnai RL 75iN and Rinnai RL 94. Rinnai is also common for designing energy efficient gas water heaters, something that most of its competitors are poor at.

Stiebel Eltron

If you love European designed products, you may want to get your next tankless water heater from Stiebel. The German company is popular both in Europe and in North America as a whole. They are known for producing high quality heaters and for infusing technology to make the heaters user-friendly.

Bottom Line

There are over a dozen popular tankless water heater manufacturers. You have tons of water heaters to choose from. But there is always the best tankless water heater for each family. Take your time to research on various heaters before you can decide if it meets your needs. Evaluate your home’s needs, installation, and budget before you can conclusively settle on a particular water heater. If you already know what kind of heater you are looking for, however, head straight to our tankless water heater reviews above and you will find one that meets your needs.

Leave a Comment

Your email address will not be published.