*If you purchase through our links, we may earn commissions at no additional cost to you.*

Best Tankless Water Heater – Top 7 Reviewed [2021]

Choosing the right water heater is very much difficult for us sometimes. When there is a lot of options in hand, we become so much confused to choose the right one. Very often people tend to spend extra bucks on buying the water heater simply not for having proper guidance. A water heater can be of varying types in terms of capacity or flow rate. It can be run by gas, propane or electricity. Because of so many varying options, the price range of water heater also varies to a great extent. In this article, we will try to find out a list of the best tankless water heater in the market in 2020. We have extensively researched more than 20 top products and made a shortlist of 7 best pick based on users’ review, rating, utility, feature, brand reputation, and price.

At the very beginning, we will be trying to differentiate between different kinds of water heater so that the readers can understand which model will be the best for their needs. After that, we will show a detailed review of your best pick tankless water heater models. Finally, we will guide the readers about some factors that should be considered during deciding to buy the machine.

We independently recommend the best products and may earn commissions if you purchase through our links.

Best Tankless water heaters

We have researched almost all available tankless heaters in the market run by electricity, gas, and propane. After systematic research, we have shortlisted 7 best tankless water heaters that are the best in 7 different categories.


ModelRheem RTGH-95DVLNEcoSmart ECO27Rinnai V65iN (indoor)Stiebel Eltron Tempra Plus 24Sio Green SIO18 v2Camplux 5L 1.32 GPMTakagi T-K4-OS-NG
Flow Rate (105F)4.9 GPM @ 27F Input water temp2.7 GPM @ 37F Input water temp3.0 GPM @ 37F Input water temp2.6 GPM @ 42F Input water temp2.5 GPM @ 37F Input water temp1.32 GPM @ 60F Input water tempNot specified
Suitable Family Sizemedium to largeSmall to mediumSmall to mediumSmall to mediumSmall to mediumLight outdoormedium to large
Fueled ByNarual GasElectricityNarual GasElectricityElectricityPortable propaneNatural Gas

EcoSmart ECO27 [Editor’s Choice]

EcoSmart is a renowned name in the field of the electric heater. The company is based in the USA. Although this is not a very old company, within a very short time, they have earned the trust of the consumers by supplying quality products and good value for money.  ECO 27 is the most popular model in the tankless electric heater segment. Among all the electric tankless electric heaters available in the market, ECO 27 is one of the most sold ones. This model is compatible with indoor uses. You can use this for your kitchen sink or bathroom shower. This is also good if you want to use this in your hotel or restaurant. If your RV and boat can supply 27W electricity, you can set it for hot water.

Key features

  • Size: 18” X 17 “ X 3.75”
  • Run by:  Electricity
  • Electric Power: 27 KW
  • Warranty: Lifetime
  • Flow rate:  2.7 GPM at 37°F input and 105°F output water
  • Temperature range: 80°F-140°F
  • Activation flow rate: 0.3 GPM
What we liked
  • Energy-saving: In comparison with the conventional tanked water heater, this machine can save up to 50% energy cost.
  • Easy installation: This model is easy to install. You can integrate and connect to your supply line quite comfortably. Therefore, if there is any need for repair, you can do it easily.
  • Higher flow rate: Among the tankless electric water heater, the flow rate is quite good. Therefore, this machine can be used in small to medium houses.
  • Small and compact: This unit will take a comparatively less amount of space to be installed.
What we did not like
  • Not recommended for a big house.
  • Electric requirements during installation might be extra work.
  • This machine is run by electricity. Therefore, it will be more expensive to operate than a gas run water heater.


If you intend to buy an electric tankless water heater, then ECO 27 must be a good option for you considering everything. This is the most popular in the market. If you do not require a huge supply of hot water, then we will recommend you to buy this unit without any doubt. No other water heater model in the market could earn so much trust of the consumer in a short period like this one.


Sio Green SIO18 v2 [Best Technology]

SioGreen is a renowned name in the water heater industry. This model -SIO18 is somewhat a different machine in terms of mechanism. Although it is run by electricity, it does not heat the water by a heat exchanger. Instead, it uses the newest Infrared technology to heat the water. This product was released in 2019.

Key features

  • Size: 20″x14″x6″
  • Run by:  Electricity
  • Wattage: 18W
  • Flow rate:  2.5 GPM at 37°F input and 105°F output water
  • Temperature range: Not Specified
What we liked
  • No heat exchanger: this means no tension of scale formation and regular maintenance. SioGreen IR260 is integrated with IR technology to heat the water. The heating tube is made of Quartz, unlike other on-demand water heaters.
  • Slim design: This is a very slim and compact tankless water heater. Because there is no heat exchanger, the manufacturer saved a good amount of space and made the machine very smart looking. This is a good fit for installing anywhere inside your home.
  • Money-back without a condition: if you are not satisfied 100% by this machine, you can return this with no condition.
  • No venting needed: as it is an electric tankless water heater, you need not install an expensive venting system for the combustion gas.
What we did not like
  • A licensed plumber is required to install the unit.
  • Users reported issues regarding warranty claim.


If your water is hard and prone to scaling, you should avoid a tankless water heater that has a metallic heat exchanger. You will have to maintain the heat exchanger regularly if the water quality is not good. In this situation, choosing a tankless on-demand water heater that heats the water without using metallic media is a better decision. SioGreen is the market leader in these kinds of products. The positive reviews from the customers confirm that newer technology will not be something to worry about. It will run smoothly.


Rheem RTGH-95DVLN [Best For Big Family]

Rheem is a renowned brand in the water heater industry. After we researched all the models of this company, we found that RTGH-95DVLN to be the best for residential use. This water heater run by gas with a small amount of electricity for functioning the system.

Key features

  • Size: 18.5 x 9.8 x 27.5 inches
  • Run by:  natural gas
  • Flow rate:  4.9 GPM at 27°F input and 105°F output water
  • Temperature range: 85°F-140°F
What we liked
  • Energy-efficient: The rated energy efficiency is 94%, which means only 6% of your energy will be drained out.
  • Intelligent energy control: This model is integrated with an intelligent energy control system. The system optimizes energy consumption to ensure maximum efficiency.
  • Activates instantly: Minimum activation flow rate of 0.4 GPM. When only one-third of the water of the faucet enters into the pipe, then the heater activates and starts working.
  • Larger capacity: Suitable for large families. Unlike electric tankless water heaters, this gas heater can serve up to 3 bathrooms at a time.
  • Automatic warning system: To make sure the safety from hazardous vent gas, this model is equipped with an automatic system that will warn you if it detects any problem.
  • Freeze protection system included that works up to -30°
What we did not like
  • This machine needs some additional accessories during installation. Though the installation process is not that difficult, finding out and buying these items incur additional time and cost.
  • The price of this unit is quite high.
  • For commercial use, this machine does not serve as good as residential purposes.


If you live in a big family, looking for a reliable option which can cover all over the home, then we much suggest you Rheem RTGH-95DVLN. The manufacturer has tried its best to offset the disadvantages of a gas run water heater. Therefore, energy efficiency and safety have been taken care of with priority.


Rinnai V65iN [The Smart Tankless]

Rinnai is a reputed manufacturer from Japan. V65iN is one of the most popular models of their tankless water heater. This water heater also has an outdoor version which is also of good quality.

Key features

  • Size: 13.9 x 8.8 x 23.6 inches
  • Run by:  natural gas
  • Flow rate:  3.0 GPM at 37°F input and 105°F output water
  • Temperature range: 98°F to 140°F
What we liked
  • Energy-efficient: Energy efficiency of this unit is 95%. This indicates a very less amount of energy is lost during operation.
  • Easy installation process: Installation of gas water heaters are usually complicated. But we have observed that Rinnai V65iN is comparatively easy to install. Especially, to set up the gas venting system, you just need a single pipe to connect with it.
  • Mobile controlling system: You can connect the machine with your mobile phone through wi-fi. This is a unique feature of a tankless water heater. This feature makes your life so easy that you can control the temperature of the water when you are scrolling the social sites.
  • Scheduling temperature: You can schedule the temperature you want. For example, if you want a bit hotter water in the morning time throughout the week then you do not need to manually do it every day. Just input the data in the system and enjoy customized hot water temperatures all week.
  • It can save up to 40% of the energy compared to a traditional tanked water heater.
What we did not like
  • This machine needs some extra equipment if you want to enjoy the full feature of it. For example, to reach the maximum temperature you need to add an extra device.
  • An on-demand water heater should give you water instantly. We have found that this unit takes 30 seconds or more to be activated for the first time. The wait time is higher than other tankless water heaters in the market.


Rinnai V65iN is a more technologically advanced tankless water heater. It is integrated with some automatic system that is symbolic to a smart home.  We recommend this water heater for a medium house having up to two bathrooms hot water connection needed.


Stiebel Eltron Tempra Plus 24 [Best For Shower]

Stiebel Eltron Tempra, a German tankless electric water heater is one of the most popular water heaters in the market. This model has quite a few sizes- ranging from 12KW to 36KW. Each of the models has similar functionality with varying capacity. This machine will give you 15-20% energy efficiency compared to a tanked electric water heater.

Key features

  • Size: 4.6 x 16.6 x 14.5 inches
  • Run by:  electricity
  • Wattage: 24W
  • Flow rate:  2.6 GPM at 42°F input and 105°F output water
  • Temperature range: 86°F-140°F
What we liked
  • Patented controlled water flow system: this unit has a very unique feature to control the water temperature. If the temperature control is out of reach, then the system will adjust the water flow rate without compromising the temperature.
  • Higher flow rate: In comparison to an electric tankless water heater, the maximum flow rate of this unit is 6.61 GPM, which is outstanding.
  • Compact design: The design of the machine is very compact and modern. It needs only a suitcase like space to install it.
What we did not like
  • As a high capacity electric tankless water heater, this unit will cost considerably more in the utility bills than a gas-fueled tankless water heater.
  • Some of the reviewers mentioned that the installation process is not easy for general people. Therefore, professional technicians might need to be called.


If you are looking for a tankless water heater to use specifically for your shower, this model will be the best out of all the models. The temperature control mechanism of this machine has made it special for a comfortable bath. But think twice before buying a high capacity electric water heater. The power consumption will be much more than a gas run one.


Camplux 5L 1.32 GPM [Best For Camping]

Of all the tankless water heater we have researched, we have found a very few of them are good for outdoor uses. Camplux 5L 1.32 GPM model is the most used and popular portable tankless water heater which is very suitable for outdoor uses such as camping, RV, outdoor shower, bathing animals, etc.

Key features

  • Size: 11.4 x 4.3 x 14.8 inches
  • Run by:  Portable propane
  • Flow rate:  1.32 GPM at 60°F input and 105°F output water temperature
  • Temperature rise: 114.8℉ to 46.4℉ (with varying flow rate)
What we liked
  • Friendly for indoor usage: Added with oxygen depletion sensor made it safer using indoor.
  • Activates quickly: Activation water pressure of this machine is very low. It starts working as low as 3psi water pressure.
  • Reasonable price: The price of this machine is very reasonable. The value for money of this unit is great.
  • Easy installation: Installation process of this machine is straight forward and easy. Therefore, professional technicians are not required.
  • Good service: Customers reviewed that the customer service of the company is very helpful if there is any problem.
  • Fire safety and anti-freezing: This machine is integrated with automatic fire safety and an anti-freezing system to ensure robust safety.
  • Portability: Compact size and lightweight of the machine have made it portable. It is so easy to handle that even a 12-year boy can carry it.
What we did not like
  • You must need to carry liquid propane to run this unit. This might be an extra nuisance.
  • This is not suitable for the bathroom and kitchen.


Camplux 5L 1.32 GPM is the best tankless water heater if you are finding out a portable one for camping or outing. The capacity of the machine is not good enough to cover up the water need for a bathroom or a kitchen. Therefore, if you think of this machine for the use of a heavy shower, you are probably taking the wrong decision. But for the outdoor uses, we have not found any better alternative to this machine so far.

Takagi T-K4-OS-NG [Best Outdoor]

Takagi is a reputed brand name for the manufacturing of water heater for more than 70 years.

Key features

  • Size: 8.5 x 13.8 x 20.3 inches
  • Run by:  natural gas
  • Flow rate:  Not specified
  • Temperature range: Not specified
What we liked
  • Higher flow rate: The maximum flow rate of the water heater is good enough to cover up to three bathrooms.
  • Space-saving for outdoor: This is an outdoor water heater. Therefore, if you are living in a small house, this can save you some space.
  • No venting required: No need to set up any gas venting system. Because you are setting it up outside, you need not install an exhaust gas venting system which is an extra hassle for indoor type tankless gas water heater.
  • Remote control included: Very few tankless water heaters we have found that has a remote controlling system.
  • Anti-freeze protection included.
What we did not like
  • Some users reviewed that they are not satisfied with the customer support.
  • Gas venting needs to be taken with extra care to ensure safety.


This water heater can be the best option for you if you are living in a small home and do not have enough space to set up the heater inside your room. On the other hand, if you are a bit more safety concern, do not want to keep a gas run heater inside your home, you can also choose this as a reliable option. You do not need to think about the water capacity because of the higher flow rate of the machine.


Do you really need a tankless water heater?

Water heater with a storage tank is very common in many houses, especially in old ones. To differentiate it with a tankless water heater, first, we should know what a tankless water heater is. Tankless water heaters are sometimes referred to as on-demand water heater. The reason is that these water heaters do not reserve the water inside a tank. Rather, with the help of a very powerful heat exchanger, the heater instantly heats the water and directly supply it to the faucet.  A person often gets confused making her decision to choose between a tank or tankless water heater during purchasing. Below are the pros and cons of both types so that it helps you make a better decision.

Advantages- storage tank and tankless

Storage tank

  • Tanked water heaters are usually of larger capacity than tankless.
  • Water flow rate is not an issue that you have to consider before making a purchase which is a big problem for a tankless water heater.
  • These are simple in construction. Therefore, easy to repair.


  • The most benefit you will get from a tankless water heater is energy efficiency. As there is no storage tank used, unlike a tanked water heater, it is necessary to heat a huge amount of water to make the heater functioning. Therefore, energy consumption is much less in a tankless water heater.
  • Usually, the service life of a tankless water heater is more than a traditional tanked water heater. If there is any issue you can easily replace the parts of the unit, this extends the life of this machine even more.

Disadvantages- storage tank and tankless


  • Standby Energy loss is a big problem for a storage-tank water heater. After the use of the heater, there is still hot water in the tank which will not be used and will remain idle.
  • These are big and occupy more space.


  • The water flow rate might be an issue. Some small capacity model of tankless water heater might not be good enough to supply sufficient hot water.
  • Although the expense of power consumption is less, the initial cost of a tankless water heater is more than a conventional water heater.

We have a full article on differences between tank and tankless water heater. You can check it out.

Gas  Vs Electric- Which one is better?

Among different types of tankless water heaters we have gas fueled and electricity fueled options. This is a very common confusion among the users to decide the suitable one. Let us find the pros and cons of both the types.

Advantages- gas and electricity fueled tankless

Gas Powered

  • The installation procedure of a gas run water heater is easier.
  • The cost of operation of a gas water heater is significantly less than an electric water heater.
  • A better output water flow rate is obtained from a gas water heater. When some of the on-demand tankless electric water heaters cannot supply sufficient hot water, then gas tankless water heaters can be the alternative.

Electricity powered

  • Generally, the energy efficiency of electric water heaters is more than 90%. This is significantly higher than the energy efficiency of the gas water heaters.
  • Electricity is a readily available source of power. Not every home has a natural gas supply to power the water heater.
  • These machines are comparatively safer to use. They need less regular inspection and surveillance. There is no risk of venting any gas.

Disadvantages- gas and electricity fueled tankless


  • Combustion gas needs to be vented of a gas run water heater. Sometimes, this can be an issue for safety. Therefore, regular inspection is necessary.
  • Gas-powered electric heaters need more space. Therefore, if you live in a small and medium-sized home, finding an appropriate location to set up the heater might be difficult.
  • Because you need to set up a proper venting system, the cost of installation of a gas water heater is higher.

Electricity powered

  • The operation of an electric water heater may cost you more than double the cost of operating a gas water heater.
  • To heat the same volume of water, an electric tankless heater takes more time than a gas heater.
  • During peak time, when the household needs a lot of hot water, an electric water heater is less efficient than a gas heater to supply sufficient water.

What to consider before buying the best tankless water heater

Let us find the most common points that must be considered before choosing a tankless water heater. The below tips can be helpful for you as a buying guide.

Deciding between Gas or Electric

At the very beginning of the article, we have discussed the advantages and disadvantages of having a gas or electric tankless water heater. We would recommend you read those carefully before making the purchasing decision. For example, if you are a heavy user, living in a big family, you should buy a gas tankless water heater to cut the cost of the utility in the long run. Gas is comparatively cheaper than electricity. On the other hand, if you are living in a small family, your hot water usage is limited, you do not like to install the troublesome gas venting system, then you can go for an electric tankless water heater.

Additional accessories

You might need to buy some additional accessories after purchasing your water heater. For example, scale inhibitor, additional pipeline, pressure valve kit, etc. Some companies might give you these for free and many of them will not. Therefore, make sure what are the components that will be necessary during installing the machine.  If you are buying an indoor gas water heater, you will need to set up your exhaust gas venting system. Therefore, ask the seller about the components you need to set it up. For an electric water heater, you might need to fulfill the electrical requirement of your water heater. For example, setting up a 240V, 120A line, etc. Make sure you have all the components you need to do this.

Your intended use

Are you a camper and looking for a portable water heater for your RV? You need to be sure that your tankless water heater can fulfill your intended use. The best tankless water heaters available in the market for the campers are fueled with propane gas with a very low flow rate. If you buy an electric water heater with higher flow, that might not be compatible with your RV. Therefore, make sure that the machine you have decided to buy can serve your purpose.

Your family size

If you are living in a big family, you need to connect the hot water line to at least three bathrooms, then you have to buy a water heater with larger capacity with a higher flow rate so that it can cover all the three bathrooms simultaneously. It is very common that people initially buy a tankless water heater not justifying the flow rate. After discovering that the unit they have purchased is not supplying enough hot water, they need to install an additional tankless water heater. This cost them even more than buying a higher-capacity water heater in the first place. Below is the list of capacity in GPM that is required for different types of water outputs for your understanding:

Bathroom faucet0.5-1.3 GPM
Water saver shower1.5 GPM
Regular Shower2-2.5 GPM
Kitchen faucet1.5-2.0 GPM
Dishwasher1.5 GPM
Washing machine2.0 GPM


Warranty conditions

What are the terms and conditions that need to be fulfilled to avail of the warranty? Make sure you have clearly understood everything. If you buy a specific model of tankless water heater, it might be written on the warranty terms that you need to install the machine with a licensed technician. The warranty for some of the models does not include labor costs. You still need to pay for something if you need any service during the warranty period. Many of the models of different companies cover warranty only for the heat exchanger. Therefore, do not misunderstand the terms. Read carefully before your purchase.

Temperature requirement

Most of the water heaters can raise the temperature to 120°F. But if your intended use necessitates more output water temperature, then you should be sure about it beforehand. Some water heaters might provide you higher temperatures given that you have installed some extra devices. Make sure what the terms and conditions are and what the additional cost is before you make the purchase.

Inlet water temperature

When you compare two water heaters, you probably see the rated water flow to understand the capacity of the heater. But keep in mind that the flow rate of a water heater is a variable number. It depends on the inlet water temperature. The less the inlet water temperature is, the less the outgoing water flow at a certain temperature. Therefore, you should compare apple to apple. Try to know what is the inlet water temperature at which the maximum flow rate is declared. Although this data might not be available on the internet, you may ask the seller directly to know this.

Maintenance requirement

Every tankless water heater requires regular maintenance. This is because of the scale formation inside the heater. Scale and sediments prevent the heat exchanger from performing well, produce an excess of heat and lower the service life. The frequency of the maintenance largely depends on the quality of your incoming water. If the water is fresh, forms less scale to the heat exchanger, you might need less maintenance. Know about these before you purchase.


Installation of your gas tankless water heater:

  1. If you have an old water heater that is outdated, you have to remove it first from the gas or electric line.
  2. Normally, the specification and requirement of the gas line of a tankless water heater are different from a traditional storage-tank water heater. Therefore, if you have replaced a traditional water heater, set up a new gas line.
  3. Check the water line requirement of both inlet and hot water. Install the waterline as per requirement.
  4. Mount your heater on the wall. keep some distance between the wall and the water heater. You can make a wooden platform having a thickness of 3-5 cm.
  5. Now install the vent as per the manual.
  6. Turn on the heater and check whether everything working well.



Where should I install my tankless water heater?

It largely depends on the type of water heater. In the market, you’ll find three different types- indoor, outdoor and portable water heater. For indoor water heater, try to connect it near the point of use. Otherwise, there’ll be a few seconds delay because the cold pipe water after the water heater has to be removed first. But if you have brought your machine for multiple faucets, then you have no option other than connecting it at the main pipeline. The water heater for the kitchen can be installed under the sink. Lastly, portable water heaters can be set anywhere as per your needs.

Should I purchase an electric or gas-fueled tankless system?

Gas is comparatively cheaper than electricity. Therefore, if you have continuous natural gas connectivity, you can choose a gas-fueled heater. It’ll save you money on operating costs. But the installation cost of a gas heater will be higher because of the need for setting up a venting system.

Can I install the water heater by myself?

If you are good at plumbing, you still might need to take help from professional technicians. Gas tankless water heaters for indoor set up are the most difficult to install because of the requirement of setting up gas venting pipes. Portable propane heaters are the easiest to install. You can set these up by yourself.

What kind of tankless water heater can I choose for RV?

You should buy a portable propane-fueled tankless outdoor water heater for RV. These kinds of water heaters usually powered by battery for ignition. The flow rate of these kinds is limited to use at most two faucets at a time which is good enough for outing purposes. The price range for these machines will be no more than 200 bucks.

If I do not maintain a tankless water heater, will the longevity be impacted?

If the hardness of your tap water is too high, the heat exchanger of your water heater will generate heat due to scale formation. Therefore, you will need regular maintenance. Every tankless water heater company will suggest you have maintenance in every 6-12 months. But if the water is very hard, you need to do it more frequently. Otherwise, the service life of the heater will be impacted.

Can a tankless water heater cover the whole house?

A water-saving shower has a flow rate of about 1.5 GPM. Theoretically, if your machine has a rated maximum flow rate of 3GPM, you can not connect it to more than two showers. In practice, you can not use more than two showers at a time but can connect your heater to as many showers as you wish. Therefore, your water heater can cover the whole house, but you need to be careful regarding how many faucets you are using at a time.


From our study of so many types and models of water heaters, we have found that many people get confused to choose the correct machine among so many options in the market. Tanked, tankless, electric, gas, propane, indoor, outdoor, portable, etc all are different kinds of options that will make you confused. That’s not the end of the story. There are multiple of reputed brands which have different models to offer you that will make you further puzzled.

We have tried to present comprehensive research on all such kinds of water heaters so that readers can make the right decision. We have found so many negative reviews of the users solely for the reason that they did not know well about their machine that produced dissatisfaction. If you do not know the suitable utility of a portable water heater then you might try to use it for heavy household purposes and ultimately end up with negativity.


Leave a Comment