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Best Tankless Water Heaters – Reviews and Ratings for 2017

Looking for the best tankless water heater reviews? Read our complete guide and reviews to make a smart decision and choose the best water heating system for you and your family from our top 5 selection.

Nowadays, tankless water heaters abound on the market. Since most manufactures claim to offer the best tankless water heater models, it can be somewhat daunting to figure out which unit would make a great buy. However, that does not have to be the case if you narrow down your list to models that have earned high user ratings. With that in mind, here are suggestions for five top rated tankless water heaters.

Rheem RTE_13-2

eco smart 27-4

eccotemp l5-2
stiebel tempra 24 plus
Rhemm RTE13
EcoSmart ECO27
EccoTemp L5
Takagi TKJr2-INNG
Stiebel Eltron
Tempra 24 Plus
Natural Gas
* 4 gpm
* 10 years warranty
* 3 gpm
* Lifetime warranty
* 1.5 gpm
* 1 year warranty
* 6.6 gpm
* 10 years warranty
* 6.6 gpm
* 3 years warranty
Our Review
Our Review
Our Review
Our Review
Our Review


Rheem RTE 13 Electric Tankless Water Heater Review

Rheem is known for manufacturing cutting edge, tankless water heaters, and one of their top selling models is the RTE 13. This electric unit was designed for point-of-use applications, so it delivers hot water on demand to fixtures installed in close proximity.

Rheem RTE 13-2

Features of the Rheem RTE 13 Electric Tankless Water Heater

One feature of the RTE 13 tankless water heater that makes it standout is its ultra-compact size. It measures about the size of a Webster’s dictionary, allowing for installation in nearly any space.

Thanks to Rheem’s low-flow activation technology, as little as 0.4 gallons per minute will be enough to activate the heating elements. This feature helps to prevent temperature fluctuations as well.

On the higher end, the RTE 13 can handle a maximum flow rate of 4.0 GPM. Majority of shower heads typically use 2-2.5GPM. An additional 3GPM would be enough to fill a bathtub. Therefore, the availability of 4GPM implies that you can run hot water in more than one location simultaneously when using this tankless water heater.

Unlike cheaper on-demand heaters, the heater exchanger of Rheem’s RTE 13 unit is made of a durable brass and copper alloy. The on-board temperature control has LEDs that signal active heating elements and standby mode.

According to Rheem’s recommendations, the RTE 13 is designed for indoor use only. The installation site should preferably be a dry location where water lines are protected from freezing. What’s more, keep in mind that this unit requires 240V power supply and 60AMPs from a grounded power breaker using a 6-gauge line. The RTE 13 also uses standard 1/2″ compression fittings and there must be at least 18” of copper tubing on both the hot and cold water lines that serve the unit.

Who Should Buy?

If you live in a region that experiences temperate weather and are in the market for a point-of-use instantaneous heater designed to serve two to three hot water fixtures, then Rheem’s RTE 13 would make a worthwhile buy. Still, there’s no perfect water heating system, and therefore here is a list of pros and cons for the RTE tankless water heater for you to weigh.


  • Easy to install
  • Compact yet powerful electric tankless water heater
  • Provides an unlimited supply of hot water
  • Low flow activation setting prevents temperature fluctuations
  • Rugged copper and brass heat exchanger


  • This unit uses up to 13,000Watts (13KW) per hour, which is a high demand compared to other home electrical appliances. On the plus side, the unit only draws power when there is a demand for hot water.
  • Water might not get hot enough when using this unit in cold climate regions because of its low temperature rise.

Rheem RTE 13-4


The Rheem RTE tankless water heater has a few drawbacks as cited above. So, make sure that this unit is what you need before making a purchase. Rheem offers a 1-year warranty on parts and 10-year warranty on the heat exchanger. However, only hire a licensed electrician for the installation to avoid voiding your warranty.

Check real user ratings and best price here!

Ecosmart ECO 27 Electric Tankless Water Heater Review

The Eco Smart 27 is one of the top selling tankless electric water heaters on Amazon, and with good reason. Equipped with smart technology, this on-demand heater has amazing features. It can be used as a whole-house or point-of-use water heater, as long as your hot water needs meet the specifications for this unit.

eco 27-4eco 27-2

Features of the Ecosmart ECO 27 Electric Tankless Water Heater

The self-modulating technology that Ecosmart uses allows their tankless heaters to regulate the energy needed to heat current flow. There are up to 3 heating elements on this unit, but each one is only activated as demand increases. The ECO 27 was designed to produce 105 degrees F at a flow of 3GPM when the temperature of incoming water is 37 degrees F. Generally, the warmer your climate, the greater the flow rate to expect from this unit.

When it comes to power needs, the Ecosmart ECO 27 requires a supply of 240V and you must have at least a 200AMP electrical panel with three double-pole 40AMP circuit breakers available. It’s easy to replace a tanked water heater with this unit since it uses standard 3/4″ NPT water heater plumbing.

A single knob on this wall mounted tankless water heater allows you to control temperature settings in increments of 1 degree F. You can also control the flow of water from anywhere in the house by buying the remote control that comes separately.

Who Should Buy?

For homes built in places with temperate climate where the temperature of ground water is at least 37 degrees For higher, the Ecosmart ECO 27 tankless water heater would make a worthwhile buy. With a flow rate of 3GPM at this low temperature, you can run two showerheads that use 1.5GPM and get an endless supply of hot water with a temperature of 105 degrees F.


  • Easy to install compared to a gas-fired tankless water heater
  • Self-modulating technology helps to conserve energy
  • Lifetime parts-only warranty
  • Small and compact size saves space


  • Homes in extremely cold climates might not be able to receive significant temperature rise with this unit
  • High demand for power both at installation and when running



Larger homes can even install more than one unit at multiple points of use if demand for hot water is high. Whether used as a point of use or whole-home tankless water heater, this unit provides good value for money. This can be attributed to its self-modulating technology, compact size and lifetime warranty on all parts.

Check real user ratings and best price here!

Eccotemp L5 Portable Tankless Water Heater and Outdoor Shower Review

The Ecotemp L5 is arguably the best tankless water heater among all portable, gas-fired models. Not only is this unit a tankless water heater, it’s also an outdoor shower. It uses liquid propane as the fuel source and 2D cell batteries to ignite the flame. Weighing about 13 pounds, this tankless heater and outdoor shower travels easily to any off-grid location, be it the campsite, barn, or cabin. It may be installed indoors as well as a point-of-use water heater.

eccotemp l5-2

Features of the Ecotemp L5 Portable Tankless Water Heater

Apart from being lightweight, the Ecotemp L5 portable on-demand water heater comes with almost all accessories required to use it. The package includes a shower nozzle, garden hose adaptor, vent shields, hardware pack and instruction manual. The only additional item to purchase besides the unit itself is a propane tank.

Ecotemp’s L5 can reach temperatures of 80 to 150 degrees F, while delivering hot water at a flow rate of 0.5 to 1.4 gallons per minute. This means that it’s only ideal as a single use tankless water heater, but a larger home can install more than one unit in different bathrooms.

This tankless water heater operates at 20-80PSI of water pressure. It features an automatic ignition, so the flame turns on as soon as water begins to flow. On the front of the unit, there are gas and water regulator dials, allowing you to control flow and fuel consumption.

Who Should Buy?

If portability is important when it comes to buying an instantaneous hot water heater, then the Ecotemp L5 might just be what you need. This portable tankless water heater is also quite affordable, but its maximum flow rate of 1.4GPM makes it ideal for low use requirements.


  • Built in spark generator runs on two D cell batteries, which makes this water heater ideal to fire up in places where there is no electricity
  • Compact size and lightweight construction allows for easy portability
  • Easy to set-up anywhere
  • Comes with accessories such as shower nozzle and garden hose adaptor


  • Some users complain that using the water heater outdoors in windy conditions can be impractical because a breeze can easily blow out the flame.


eccotemp l5-3


The Ecotemp L5 is one of the top rated water heaters on Amazon. Therefore, it’s certainly worth considering if you’re in the market for a portable, low use requirement, tankless water heater. Ecotemp provides a limited warranty of 1-year on parts as long as your unit remains in place at its original point of installation.

Check real user ratings and latest price here!

Takagi T-KJr2-IN-NG Indoor Tankless Water Heater Review

Takagi is known for their sleek design and feature rich tankless water heaters. The Takagi T-KJr2-IN-NG indoor water heater is the most compact unit from their line-up. However, this model is larger than many electric tankless water heaters.


Features of the Takagi T-KJr2-IN-NG Indoor Water Heater

The T-KJr2-IN-NG Takagi indoor tankless water heater can easily meet the needs of full home with up to 3 bathrooms. It delivers up to 6.6 gallons of hot water per minute, and has inlet and outlet thermostats for constant temperature monitoring. Having this unit is akin installing a 40-gallon tank water heater. However, the Takagi T-KJr2-IN-NG is more energy efficient than the traditional tank style water heaters. It only uses gas when there is a demand for water and has an energy saving factor of 81-83%.

Measuring 6.7 x 13.8 x 20.3-inches, this tankless water heater may be wall mounted or installed under a sink. When installing this unit, you’ll need to hook it into a ¾” gas line and a 4” category III stainless steel venting system is required.

Who Should Buy?

This tankless water heater is ideal for families with 3 to 5 people. Its ability to deliver 6.6 gallons per minute makes it possible to run multiple hot water fixtures at the same time.


  • Equipped with Air Fuel Ratio Sensor (AFR) and Water and Exhaust Temperature Safety Control
  • Capable of delivering water at a high flow rate of 6.6GPM
  • Maintenance required only once a year
  • Performs well even in areas with chilly climate


  • Installation requires a venting system



While the Takagi T-KJr2-IN-NG tankless water heater may be expansive and has special venting requirements, it’s a cost effective solution to your long-term water heating problems. This unit is perfect for average sized families and performs well in both mild and chilly weather. The best part is that it comes with a 10-year limited warranty on the heat exchanger and 5-year warranty on parts.

Check real user ratings and latest price here!

Stiebel Eltron Tempra 24 Plus Electric Tankless Water Heater Review

The German made Stiebel Eltron Tempra 24 is an electric whole on-demand water heater that’s touted as the most technologically advanced tankless system. Since Stiebel Eltron redesigned the Tempra series, water heaters from this line up now come with upgraded heavy duty electronics, single flow sensors, and easily accessible hinged cover. The Tempra 24 has all of these features and other amazing factions that will be discussed in this review.

stiebel tempra 24 plus

Features of the Stiebel Eltron Tempra 24 Plus Electric Tankless Water Heater

The Tempra 24 plus electric tankless water heater from Stiebel Eltron has several advantages over gas type units. For starters, it’s cheaper and easier to install than compared to similar gas type models.

In order to function properly, the Tempra 24 requires two 60 amp circuits and a 208/240 V power supply. Once these prerequisites are in place, you can start to enjoy an endless supply of hot water. However, this heater only allows you to run two hot water fixtures at the same time. It has a maximum flow rate of 4 gallons per minute, so running more than 2 hot water appliances may be pushing too far. Depending on the temperature of incoming water, this unit can heat water up to 140 degrees F.

Who Should Buy?

The Tempra 24 plus electric on-demand water heater is perfect for small homes that need to run two hot water fixtures at the same time such as a shower and dishwasher. Keep in mind, though, that the flow will drop when running more than one hot water appliance. As far as the pros and cons for this tankless hot water heater are concerned, here is what to expect.


  • The unit’s Advanced Flow Technology ensures consistent temperature output
  • 99% energy efficient
  • Requires little to no maintenance
  • Easy to install as long as you meet the water heater’s electrical requirements
  • Digital temperature control with easy to use dial and colored chart


  • Slightly more expensive than other models
  • Additional electrical work may increase installation costs. This only applies if your home does not meet the water heater’s electrical requirements.
  • May not perform well in cold climates

stiebel tempra 24 plus-2


The Stiebel Eltron Tempra 24 Plus Electric Tankless Water Heater can serve most low usage requirements just fine. It’s a decent choice if you are looking for an on-demand water heater that maintains the temperature of hot water at the claimed flow rates. Users get a limited 3-year warranty, but remember to hire a licensed electrician to avoid warranty issues.

Keep in mind that there are many other models on the market besides the tankless water heaters suggested in this guide. Whether you prefer an electric or gas powered model, ensure to read tankless water heater reviews to learn what other users have to say about various units that you intend to buy.

Check real user ratings and latest price here!


How Tankless Water Heaters Work

Any functioning household needs a constant supply of hot water be it for showering, washing dishes, or laundry. This is why hot water systems have become indispensable household fixtures, and not surprisingly, most homes use the traditional heaters that store hot water in an insulated tank. However, these models are now being fast replaced by tankless water heaters.

So, what is a tankless hot water heater? Well, as the name implies, these types of heating systems do not heat water and store it in some kind of reservoir or tank. Instead, they heat water instantly as it passes through the system. As a result, these units also go by many names such as “instantaneous”, “continuous”, “point of use”, or “on-demand water heaters”.

Tankless water heaters provide several advantages over their tanked type counterparts. In order to understand the benefits they offer, it’s first important to learn how on-demand water heating systems function.

While there are many brands and models of tankless water heaters, all of these units share a few similar traits when it comes to their basic functionality.


how it works


Tankless water heaters can use either electricity or gas as the source of energy. Cold water enters the tankless heating system through an inlet pipe and when there’s a demand for water (for example if you turn on a hot water showerhead or faucet), this activates the heating elements. For gas tankless water heaters, a pilot light or electronic ignition sparks up to ignite the flame upon sensing water flow.

A tankless water heater that uses electricity simply converts electrical energy into heat. The heating elements are usually placed in direct contact with hot water in a heat exchanger that houses highly coiled copper tubes. So, as water passes through this copper honeycomb, heat is directly transferred into the flow.

In a gas powered instantaneous/tankless water heater, fuel and air simultaneously enter into a combustion chamber. This happens as soon as water starts to flow into the system and then the ignition source turns on the flame. The combustion chamber sits just above the heat exchanger, thus allowing combusting gases to raise the water’s temperature as it flows through the copper coils.

Depending on the model, tankless water heaters may have gas valves, variable speed combustion blowers, water flow sensors, thermostats, and electronic boards to control the whole process of heating water. These components automatically adjust incoming gases, oxygen, or electric heating elements to heat cold water to your preset temperature or meet the water heating demands.

If there’s a low volume of water flowing through the system, less gas burn inside the combustion chamber. In the same way, more fuel flows to the burner so that a larger flame can adequately heat water when the flow is high.

In a condensing tankless water heater, there’s usually an additional component called a secondary heat exchanger. Water passes there before entering the primary heat exchanger. Tankless water heaters with this kind of configuration capture any latent heat before it escapes into the vent system.

Once water leaves the primary heat exchanger, it comes out hot through an outlet pipe. The flow is then distributed to fixtures where hot water is needed. Electrical heating elements in an electric tankless water heater turn off the moment water flow stops. When cold water stops entering a gas-fired unit, the combustion fan may continue to operate at a low speed before the flame goes out completely. This allows any leftover exhaust gases to be expelled through the tankless water heater’s flue system.


Exploring Tankless Water Heaters By Fuel Type or Energy Source

Generally, tankless hot water heating systems come in two varieties – whole house and point of use heaters. Whole house systems tend to be more expensive, larger and they’re usually powered by propane or natural gas.

On the other hand, point-of-use tankless water heaters mostly use electricity. Such heaters tend to be small and only heat water for one or two outlets. Due to their small size and heating capacity, point-of-use tankless heaters are normally installed close to hot water fixtures. This in turn helps to prevent loss of heat due to lag time, or the duration it takes hot water to reach a faucet.

There are several factors to consider when deciding which type of tankless water heater to go for and what energy source to use. We’ll take a closer look at those factors in this section so that you can make an educated decision when it comes to buying a tankless water heater.


Pros, Cons and Purchasing Considerations for Tankless Water Heaters

All the various types of tankless water heaters have their own set of advantages and disadvantages. However, no single model is better than the rest because certain tankless water heaters are more effective for specific applications.

For example, electric on-demand water heaters perform poorly in mountainous and northern regions or anywhere with a particular harsh winter. The reason for this is that extreme cold has been found to damage or compromise electrical components. On the plus side, electric tankless water heaters are less expensive, more efficient, easier to install, and generally require less maintenance than their gas fired counterparts. But their low heat output limits their usage to point of use heating systems where hot water does not have to travel far to reaches faucets.



Tankless water heaters that use gas may be less efficient, more expensive, a bit difficult to install, and require more maintenance than electrical modes. However, their monthly operating costs tend to be lower and they have a high heating capacity. Since gas-fired tankless water heaters have more juice (heating capacity) than electrical models, they are generally used for whole house hot water heating systems. These models also function well in both temperate and cold climates.

Should you decide to settle for instantaneous water heaters that use gas, there are still more considerations to make. First, you must decide whether to go for a unit that uses propane or natural gas. In this case, it’s prudent to compare which type of fuel is cheaper and/or more readily available in your local area.


How to Size a Tankless Water Heater

Sizing a tankless water heater can be a bit tricky. But once you know what to consider, the process is not that hard to understand. It’s never a good idea to attempt under sizing these types of hot water heating systems just to save money because you risk not meeting the desired water heating demands.

The following are the steps to follow when it comes to choosing what size of tankless water heater to settle for.

Step 1: Determine Your Maximum Flow Rate

It’s important to note that a tankless water heater does not run out of hot water unless the flow exceeds its ability to heat incoming water. This means that as the demand for hot water (or flow rate) increases, the tankless water heater’s ability to raise temperature drops (and vice versa).

To get a better picture of what this means, think of it this way: A tankless water heater may be able to keep up with the flow when running one showerhead and a hot water faucet at the same time, but turn on the washing machine and you’re now in for a cold or lukewarm shower. The reason for this is that the tankless heater won’t be able to heat the large volume of water that passes through it so quickly.

Therefore, when sizing tankless water heaters, flow is one of the variables that must be factored. To be more precise, on-demand water heaters are usually rated based on the maximum temperature rise they can deliver at a given flow rate.

The flow rate is the amount of water that you need to heat when using an on-demand water heater, which is usually measured in gallons per minute (GPM). If the tankless water heater is going to serve more than one fixture, you need to determine the maximum amount of flowing water the system can heat up adequately. This simply means adding up the flow rates for all hot water fixtures that may be running at any given time.

For example, let’s assume that you plan to simultaneously run a showerhead and hot water faucet at a bathroom sink each with a flow rate of 2.6GPM and 2.2GPM respectively. In this case, you should look for a tankless water heater that can handle a flow rate of 4.8GPM.


Step 2: Compute Temperature Rise

Temperature rise is the difference between the temperature of incoming water and the desired output. For example, you might discover that the average temperature of cold water entering the hot water system to be 50 degrees Fahrenheit. This value can vary drastically from one area to the next. However, ground temperature is roughly the same as the average yearly air temperature for a given geographic area.

Once you know the temperature of incoming ground water, simply subtract this value from the desired output temperature. For most domestic applications such as washing dishes, laundry and showering, a temperature output of 100-120 degrees Fahrenheit should be sufficient. So, from 50 degrees Fahrenheit, you would need to heat incoming water by an additional 70 degrees Fahrenheit to reach a peak target output of 120 degrees Fahrenheit.


Step 3: Match Tankless Water Heaters with Your Heating Requirements

Armed with temperature rise and total flow rate, you can check out specifications for different types of tankless water heaters to determine which size would best meet your needs. The rating or sizing specifications for an on-demand tankless water heater would quote something like 8GPM at a temperature rise of 45 degrees F. Some smart system tankless water heaters have the ability to limit flow rates in order to maintain the set temperature so be on the lookout for such models as well.


General Pros and Cons of Tankless Water Heaters

As mentioned earlier in the introduction of this guide, tankless water heaters provide a number of advantages over their tank-style counterparts. These units also have some drawbacks when compared to other types of water heaters. Knowing the pros and cons of on-demand water heaters is vital. This will help you know what to expect should you decide to go for these types of water heaters.



  • Energy Efficient

Traditional tank water heaters usually peak at around 140 degrees F (60 C) so that the water supply remains hot for longer periods. Since pumping water out of a shower or faucet at this temperature would not be safe let alone comfortable to use, cold water is usually added to the flow. A lot of energy goes to waste as well as tanked water heaters remain in standby mode to keep the water warm or hot enough to use after long periods of storage.

However, on demand water heaters are more energy efficient than the tank style models. These models do not store water in anticipation for demand, so there’s no need for a tank. By heating water only when it’s needed, and no storage tank to heat and re-heat water, tankless water heaters conserve more energy and can lead to significant savings in your utility bills.

  • Long Lasting

Another problem with traditional water heaters is that the tanks these units use to store water tend to degrade and start leaking over time. Since tankless water heaters do not have a reservoir for holding hot water, they’re much less susceptible to the burdens of aging. Some models can even outlive the house they are installed and that is why most manufacturers offer warranties ranging between 20-25 years.

  • Space Saving

Since no large tank is required to store hot water, on-demand heaters can be very space efficient. Some brands even design models that can be the size of a small suite case. Thanks to their compact designs, tankless water heaters allow for installation in non-traditional spaces such as attics, crawl spaces or on the exterior and interior side of walls.

  • Increase Home Value

While their high installation costs may be seen as a constraint, think of these units as some form of investment since they increase your home’s value should you have plans of selling in the future.

  • An Endless Supply Of Hot Water

On-demand water heaters never run out of cold water as long as the total demand for water does not exceed their maximum flow rate capacity.



  • Costly to Install

By virtue of being more energy efficient, tankless water heaters cost more than traditional tank type models. However, the set up costs far outweigh long-term savings you’ll get from using a tankless hot water heating system.

  • Temperature Fluctuations At High Flow Rates

Large tankless water heaters may be used to heat water for a large house, but there may be some drop off in temperature when multiple hot water appliances are used at the same time.

One way to mitigate temperature loss is to install small point-of-use tankless heating units to serve each area in a home. The initial cost of installing multiple units may be high than the traditional solution, but energy costs can drop by 10% to 20%, resulting in significant savings over time.

  • Electrical Units May Not Function Properly In Cooler Areas

You may need to use a gas powered tankless hot water heater to avoid poor performance from an electrical unit if live in areas that experience cold climate.

Basic Installation Requirements for Tankless Water Heater

There are certain requirements that must be adhered to when it comes to installing a tankless water heater. Failure to meet these requirements may lead to improper operation, a compromise in safety, or voiding of the warranty. Most manufacturers specify the installation requirements for each model on their websites or installation manuals that you can download online.

Installation requirements for tankless water heaters may vary depending on local laws, the type of unit you wish to install and the chosen brand. For example, if you’re planning to install a gas or propane on-demand water heater, make sure to follow all local codes. Such water heaters may also have special venting requirements. The reason for this is that tankless gas water heaters use fans to draw in air from the outside and expel exhaust gases through a flue system. These types of gas-powered instantaneous water heaters may vent through the roof or sidewall. So, you should be prepared or in a position to make some home modifications to accommodate venting system of a gas-fired tankless water heater.

For electrical tankless water heaters, it’s important to ensure that your home has enough electrical capacity to power such units. If any upgrades will place an added demand for electrical output, such requirements should be noted as well.

Some manufactures have specific details about installation sites for tankless water heaters. For instance, you may need to ensure that the appliance will have an installation spot where any leakages won’t cause damage to lower floors or nearby structures, although that can be avoided with a drain pan. Installation sites also must be well ventilated and free of objects that restrict airflow when dealing with a gas tankless water heater.

It’s best to hire a certified technician rather than making the installation of your tankless water-heating appliance DIY project. This way, you can get specific guidelines regarding installation requirements and ensure your own safety. More importantly, most manufacturers won’t honor warranties if your system is not installed by a licensed professional.


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