9 Best Tankless Water Heater – Ultra Experts Buying Guide & Reviews

Water serves as the most important source in our daily life, especially the hot water, we need it in taking a bath, washing hands, doing laundry, and for all kinds of washing machines.

In the past, a tank water heater occupies a large space in our hot water use, but the invention of the tankless water heater has totally changed the way people in getting hot water.

You can just turn on the tap, no matter for the showerhead or kitchen faucet, there will be flawlessly hot water to meet your demand.

With the instant heating performance and endless hot water supply of on-demand water heater, the best tankless water heater is becoming more and more popular and widely used.

Table of Contents show

What Is the Best Tankless Water Heater on the Market?

What Is a Tankless Water Heater?

The tankless water heater is a heating machine used for providing constant hot water and can be widely used for residential, commercial, RV, outdoor traveling, camping, and fishing, etc.

The best heater heats water in a second, it offers endless hot water once you turn the tap on. The flow rate is quite stable and consistent. According to the professional test, using a tankless heating system is able to save 22% in operating costs each year.

If you have a large family with multiple bathrooms and faucets, choosing a large flow and best unit will help you eliminate the trouble of waiting for hot water on a busy morning. Thus it has become more and more popular all around the world.

best value tankless water heater

What Is a Good Tankless Water Heater

Compared with a tank water heater, the tankless type is excellent in its instant heating performance and compact shape. Therefore, the major consideration of getting a good tankless hot water system is its size and working performance.

Now on the market, there are many types of efficient water heaters designed for different applications and needs, cold areas, warm areas, large family of multiple people, small studio, residential use, outdoor camping use, point of use… Therefore, it is hard to define which exactly one is the best one, what you need to consider is your actual needs and budget, the one that suits your needs most is, of course, the best one for you.

Top 9 Tankless Water Heaters Comparison Chart

How It Works

A tankless water heater heats water through electric heating elements, and controls the temperature, flow rate or power, etc through the circuit, so as to get the suitable temperature for showering or other uses.

Nearly all the best instantaneous hot water heaters are equipped with self-modulation technology, it activates at a certain pressure level, and heats water only when hot water is needed. Because of its instant performance, it is also called an instant hot water system or on-demand heating machine.

tankless water heater system
how it works


1. Instant hot water supply

A tankless hot water system heats water in a second, it does not storage cold water inside but turns on whenever you use hot water. Also, it provides endless hot water for you, eliminating the embarrassing situation of running out of water in bathing. Therefore, it is suitable to be used for barbershop, hospital, and schools wherever needs constantly hot water for a long period of time.

2. Energy efficient

Unlike the tank type, the instant heat water heater eliminates the heat energy loss in preheating. Because no water is stored in a tank, there is also no extra energy loss of unused hot water. It is proved that an instant water heater saves 10%-30% energy and electricity each month.

3. Safe and environmental friendly

Safe is regarded as the primary factor to all the heating machine manufacturers, in order to guarantee the safe working condition, they designed many safety measures and systems such as overheating system, leakage protection, and the digital control, etc.

4. Small and compact shape

As no storage tank and insulation are needed, hot water boilers are normally light weighted and are small enough for small studio use, some of which are even as small as a magazine.

Apart from the compact shape, the tankless hot water heater is also designed sleek and easy to be installed, many types and colors can be chosen.

5. Stable water temperature

The temperature of the tankless water heater is quite stable, and there are also advanced types to control the temperature automatically.

6. Long life expectancy

For on-demand heating system, the cold water is heated without passing through the heating element, which is called live water, thus no limescale is left on internal parts. That is why a water heater hardly needs maintenance.

Apart from this, temperature rise in the heating process is relatively low compared with tank type, thus it does little damage to the machine. Normally the service life of endless hot water system is 2-3 times more than tank type. A best instant water heater can be used as long as 20 years.

best performing tankless water heater

Best Tankless Water Heaters Reviews

In order to help you get the most suitable and top-rated types, we made a review of the best instant water heaters on the market of 2020 and made a detailed comparison on each type of hot water boilers as follow:

1. Best For Small Home – Rheem RTEX-13 240V Heating Chamber Electric Residential Heater

best tankless water heater
Rheem electric water heater reviews



This unit is the hottest selling type on Amazon and can be listed on the top-recommended best buy one.

  • Perfect for small studio

It is a small flow rate one, rating up to 4 gallons per minute and this is perfect for single bathroom use only. You can also use it as a point of use heater, so as to shorten the waiting time for hot water.

  • Easy operated digital control

The external digital temperature setting makes temperature adjustment easier, error codes and current temperature of water readout on the screen, and you can adjust it in an increment of 1 degree a time.

  • Short waiting time for hot water

The heating time or in other words, the waiting time of it is pretty fast, takes about 15 seconds for hot water flowing to the hand sink. And temperature stays stable during the using period even for long time use.

  • Easy to install

Multiple stranded wire makes the connection of it much easier, and it takes about only 1 hour to hook it up all by yourself, but remember to follow the instructions all the time in installing for safety.


  1. Affordable and unbeatable price
  2. Low energy costs
  3. Fewer energy savings
  4. 4 pounds lightweight and compact shape saves much space, perfect for studio family
  5. Water stays the same temperature for a long period
  6. Easy for installing


  1. Not suitable for whole-house use, which supports one bathroom or one faucet a time

2. Best Space-Saving – EcoSmart ECO 27 Electric Instant Hot Water System



EcoSmart hot water heating system is always designed as compact and small shape, that is perfect to install anywhere you want.

  • Wide temperature range

The temperature range of it is between 80 and 140 degrees F, it is capable of heating 3 gallons of water flow per minute at its lowest temperature. It is ideal to be used in the northern part where the incoming temperature reaches as low as 37 degrees F.

  • Two showers support

It processes a 3GPM flow rate in cold weather and it reaches up to 6 GPM in warm areas, thus it is capable of supporting two showers simultaneously. When you turn the machine on, it provides flawlessly hot water for you even for a long period of use, you do not need to worry about running out of hot water in bathing any longer.

  • Excellent quality level

The unit is well made, all the heating elements are easy to be replaced. Copper and stainless steel components enable its high corrosion resistance and heat resistance.

  • Super energy efficient

It is equipped with self-modulating technology, it draws energy only when you need it, thus for a long period of use, it saves about 50% on water heating costs.


  1. Work for whole home
  2. Unlimited hot water supply
  3. Self-modulation system equipped to save energy
  4. Well made unit
  5. Easily operated temperature control, adjust with one increment a time
  6. Save 12 cubic feet after installation


  1. The temperature cannot be set as right as EcoSmart promises
  2. Unable to produce pipe hot water at a high flow rate

3. Best For Shower – Rinnai V75IP 7.5 GPM Indoor Low NOx Tankless Propane Water Heater

best tankless water heater review
best Rinnai water heater



Rinnai is a world-famous brand in producing the best tankless water heaters. This unit adopts propane as a major power and needs venting for indoor installation.

  • Powerful design

It is a relatively powerful machine, maximum BTU is 180000 and flow rate reaches as high as 7.5 gallons per minute, able to support two bathrooms use the same time. It is especially suitable for a small or middle-sized family.

  • Easy installation

The installation of it is pretty easy and straight forward if you know a bit of plumbing and have good copper soldering skills. If not, then you can find a professional to help you, Rinnai promises to offer ten years warranty for heat exchanger and five years for other things.

  • Endless hot water

The waiting time for hot water is pretty short, takes only a few seconds and you can enjoy endless hot water. But the working noise can be heard clearly because of its propane power design.

  • Low NOx design

For indoor installation, you need to install venting facilities to let out wasted gas, and for venting instructions, you may get more information from manufacturers. The low NOx design helps reduce much carbon dioxide emissions.


  1. Easy installation
  2. Pretty powerful machine
  3. Additional controller available
  4. Ten years warranty for heat exchanger
  5. Handle 2 showers the same time
  6. Perfect for middle and small size family use


Working noise is a bit loud

4. Best For Large Family – Rinnai RUC80iN Ultra Series Tankless Heater

the best tankless water heater reviews
Rinnai tankless water heater



This is another series of Rinnai that listed on reviews of the best units, compared with V75IP series, this is pretty powerful and can be used for commercial heater also.

  • The high temperature for commercial use

The temperature range of this unit is between 98 and 140 degrees F, but if used for a commercial heater, the temperature raises up to 185 degrees F with a commercial remote, but you need to buy it separately.

  • Large water flow rate

Maximum flow rate is 9.8 GPM, which is a relatively high flow rate, and is capable of supporting three or four bathrooms use the same time in the southern part or warm regions. Once you warm it up, it will provide constant hot water for you.

  • High efficient

The power requirement of the unit ranges from 15200 to 199000 BTU per hour, and thermal efficiency is up to 0.95. Therefore, it is powerful enough to use for large family use and its high efficiency saves many heating costs for you each month.

  • 2 venting options

It offers two options on venting, both concentric PVC and twin-pipe so you can choose one that is easy to be installed. The heating time is pretty fast, takes about 20 seconds.


  1. Quiet working condition
  2. Offer 2 options for venting
  3. High flow rate
  4. Commercial use available
  5. High energy efficiency
  6. Need only 2 watt to keep machine up and running


  1. Difficult to install, you need to get a professional on installation

5. Best Propane – Takagi T-KJr2-IN-LP Indoor Type

best tankless water heaters 2018
Takagi tankless water heater



This unit is regarded as the lightest and smallest among all the Takagi line of products, thus it is a perfect one for small studio use.

  • 6.6 GPM flow rate

The flow rate of it is 6.6 GPM, in winter or cold regions, it drops to 3-5 gallons per minute. No matter for the climate or season, it can always provide constant hot water for you.

  • High-temperature support

The temperature range of it is up to 150 degrees F, the power input requirement is 140000 BTU per hour and thermal efficiency is 81%. It is not powerful enough for whole house use, but you can use it for small studio or point of use type.

  • High efficiency

It is a propane type, so you need to get venting kits to help to let out waste gas, thus the upfront costs may be high, but for long term use, it is still able to save a large amount of money in heating costs because of its high energy efficiency.

  • Long service life

Without tank equipped, the heater turns on only when you need hot water, thus no corrosion occurs inside the internal material. It proves that this one can be used for quite a long time and needs minimal maintenance in its using period.


  1. Easy to install
  2. Light weight and compact shape design
  3. Digital remote available
  4. Suitable for middle size or small house
  5. Large temperature range


  1. The working noise is pretty loud

6. Best Advanced with Efficiency – Stiebel Eltron Tempra Plus 24 kW Tankless Water Heater

the best tankless water heater on the market
Stiebel eltron tankless water heater



This is an electric instant heat water heater and needs 240v power for operating. Though small in shape, it is powerful enough for commercial use.

  • 5 GPM water flow

This unit has the power of providing about 5 gallons of water per minute and raises the water up to 54 degrees F at 3 GPM. It works in ideal performance in an area where supplied water is under 45 degrees F. When used in southern part or warm regions, it supports two bathrooms the same time easily.

  • Technologically advanced design

This unit is equipped with self-modulating technology to heat water only when you need it, and an advanced flow control system controls constant temperature and water pressure in different flow levels, which is suitable for people in demand of occasional hot water.

  • Full power modulation

It supports full power modulation, 99% energy efficiency enables nearly no water is wasted in the using process. Besides, it is designed with high-level electronic parts and equipped with a reliable cover.


  1. Quiet working condition with no mechanical switches
  2. The advanced built-in flow control system
  3. Compact design for small studio
  4. High efficiency
  5. Used widely for commercial property and home
  6. Full power modulation


  1. Difficult to install, need 240v power and heavy-duty wiring
  2. Unable to install more heating elements inside

7. Best Smart – Marey ECO150 220V/240V-14.6kW Tankless Water Heater 

list of best tankless water heaters
best buy the tankless water heater



This unit is another electric type that is used under 220v or 240v with 14.6 kW. It is designed with smart technology on saving energy.

  • Corrosion resistance element

It is said to be the only one on the market to include a German-designed and patented heating element with a stainless steel water channel. Thus it is highly corrosion resistance and eliminates hard water largely.

  • Easy operated

An LCD panel is set to adjust the exact temperature you want, it operates easy and can add temperature one degree F a time. The maximum of it is up to 41 degrees F at 2.5 GPM water flow rate.

  • Stylish compact shape

The small and compact shape enables you to install it anywhere that is possible and supports two sinks or one shower the same time. It requires 220v to 240v and 70 amp double pole breaker for operating.

  • Easy installation

Installation of it is pretty easy and is able to offer constantly hot water for you. You can also use it for indoor point of use or outdoor travel use because it weights extremely light, only 10.1 pounds.


  1. Less energy consumption
  2. Corrosion resistance component
  3. Space saver
  4. Light weight and compact shape
  5. Easy to install and provides steady hot water
  6. Activate by pressure from 5 to 85 PSI


  1. Not powerful enough for whole house use

8. Best For Outdoor Installation – Rheem RTG-95XLN 9.5 GPM Low NOx Tankless Natural Gas Water Heater

best tankless water heater you can buy
Rheem tankless water heater



This one is also a powerful heating machine, that is able to be used for a large family or even commercially.

  • Large flow rate

The flow rate of it is up to 9.5 gallons per minute, thus it is perfect to support three or four bathrooms use the same time in warm areas and two bathrooms in cold regions. Once heated up, it provides flawlessly hot water for you and you can hardly run out of water in bathing.

  • No venting kits required for outdoor installation

It is both propane and natural gas available, if lacking proper gas line, you may choose propane type. It needs to be installed outdoor and thus no venting facilities are required, saving much upfront money for you.

  • High thermal efficiency

The thermal efficiency of it is pretty high, up to 94%. Together with the low NOx design, it produces less carbon dioxide gas and saves a lot of money on heating costs each month.

  • Remote control

The EcoNet smart home technology supports remote control via app, so you can easily turn the machine on and off as well as adjusting the temperature when staying indoors.


  1. Propane and natural gas both available
  2. Remote control via an app
  3. High energy efficiency
  4. Dual stainless steel heat exchangers, give the option to connect both vents when water demand is high
  5. Large flow rate
  6. 10-year warranty for heating parts


  1. Needs to be installed by professional

9. Best Condensing – Noritz NRC661-DV-NG Indoor Direct Tankless Hot Water Heater

what is the best tankless water heater
Noritz tankless water heater



This heating machine is a condensing type, which means most gas is used and seldom energy is wasted, thus saves much money on heating costs.

  • Large flow rate range

The flow rate range of it is from 0.5 to 6.5 gallons per minute, supporting 2 bathrooms used in southern parts and 1 and a half bathrooms in northern parts. The working of it is pretty quiet, you can hardly hear the noise in working.

  • High energy efficiency

The gas consumption runs between 15000 and 120000 BTU per hour, and thermal efficiency reaches as high as 93%. Low NOx design ensures less energy loss and saves a lot of money on heating costs.

  • Two venting choices

There are two heat exchangers that can be chosen, one is made from the copper while the other is from stainless steel, it can be vented with schedule 40 PVC pipe and fittings. Noritz promises to keep 12 years warranty for the heating parts.

  • Freeze protection system

Freeze protection system protects the machine from getting frozen in cold climate, it automatically takes action when senses the cold weather. Besides, you can also control the temperature remotely but you need to buy the controller separately.


  1. Compact shape
  2. Freeze protection
  3. Double venting options
  4. Quiet working condition
  5. High energy efficiency
  6. Easy installation


  1. Coldwater sandwich

Tankless Water Heater vs Tank Water Heaters

Instant hot water system and tank water heater are two types of heating machine that are frequently used in our daily life. The conventional type is tank heater, water stored in the storage tank and you need to wait a quite long time for the water being heated up. It uses a large capacity storage tank to solve the contradiction between small heating pressure and large using capacity. And when you choose a tank water heater, you need to estimate daily hot water use to determine which capacity you should choose.

The hot water system is a relatively new and advanced heating machine. It heats water without storing cold water in the tank.

Both of the tankless water heater and tank water heater have their advantages and shortcomings, here we made a detailed comparison between the two so you can make a clear determination on which one to choose based on your needs.

water heater vs tankless
tank or tankless water heater

1. Appearance

The instant heater is designed small, and lightweight, some even weight 10 pounds so you can install and use it even when going out for traveling. The colorful design and multiple shapes give you more choice in choosing.

The tank water heater is large in size because of its tank, the design of it is normally single, nearly all of the tank types are designed into white round or square types. So the options on appearance are quite single.

2. Price

Tank water heater price is largely influenced by its capacity, the larger capacity it gets, the more expensive it will be.

On the other hand, a tankless water heater price varies according to its types and performance. But of course, the portable or point of use types are much cheaper than whole-house type.

3. Installation

The instant heater has some requirement on water pressure, circuit and electric or pipelines.

A tank water heater has a requirement on the wall load bearing but has no requirement of power.

4. Using experience

A tankless hot water heater can constantly provide hot water and is quite convenient, it saves water and electricity to a large extent. Because no waiting time is needed on heating cold water, it also saves much time for you, especially on the busy morning. But in winter, the temperature rise is not stable.

A tank water heater heats the water slowly, you need to wait for at least half an hour waiting for hot water, the preheating time is quite long. Also, it has the trouble of running out of water in bathing and temperature is not so stable. The unused heated water is stored in the tank for a long time, thus the large sum of water is wasted.

5. Maintenance

A tankless hot water heater heats water when you need it, thus no heat loss and circulate heat situation occurs and thus is more efficient. It heats water directly thus no limescale is left inside the machine. Thus it needs little maintenance.

Tank water heater stores water in a storage tank, when it is used for a long period of time, much limescale will be left on the water tank and pipeline, so it needs regular maintenance and cleaning.

best tankless hot water


There are many types of tankless water heaters on the market for different applications and using conditions.


According to the usage, there are whole house heater, point of use instant heater, RV use heater, commercial heating system, and instant hot water system for a camper.

1. Whole-house tankless water heater

Whole-house tankless hot water heater refers to the machine that is powerful enough to support multiple bathrooms and faucets use the same time. The flow rate and power requirement are quite large and of course it more expensive than a point of use or small type. We have made detailed best whole house heater reviews for you, please feel free to check out on it.

2. Point of use tankless water heater

Point of use type is used mainly for small studios or to support one bathroom or one faucet a time. The flow rate is quite small and less powerful. It is relatively small in shape and can even be installed in an underwater sink. If you want to know more details, please look at the best point of use heating system reviews.

3. RV tankless water heater

RV (recreational vehicle) is used mainly for outdoor travel or camping, anyway, a tankless water heater for RV can be installed on the vehicle and used on your travel way. Most of the RV heaters are designed into electric and propane types for convenient use. Click the best RV use heater reviews for more.

4. Commercial tankless water heater

A commercial use heating machine is widely used for hotel, hospital, bath center and schools, etc. The demanded flow rate and capacity are quite large, and it needs a constantly hot water supply. You can cascade several of them together if one single unit is not powerful enough. For more information, click our best commercial water heater reviews.

5. Tankless water heater for camper

Tankless water heater for the camper is similar to RV type to some degree, but camping heater needs to be lighter in weight for convenient carrying. Also, as it is installed and used in complicated situations, the requirements of it are different a lot. You can get more information on our best heating machine for a camper.

best rated tankless hot water heater
RV tankless water heater


According to the size, there are small and portable types. As the size of the hot water heating system is all compact, so we do not talk about large types here.

1. Small tankless water heater

Actually, a small instant hot water system does not only mean the small shape but also for its small flow rate. Some of the tankless types are designed to compact in shape, yet get the same size as whole-house type do. The small unit is normally used for small or middle size studios, cabins, or garage. Please feel free to get more details on the best small type reviews.

2. Portable tankless water heater

As the name suggests, the portable units should be light-weighted enough so that you can take it anywhere that is possible. For most occasions, a portable tankless water heater is used for travel, camping or you can also use it as a point of use heater at home. A flow rate of it is small and supports one single bathroom or even only one faucet a time. Check the best portable reviews for more.


According to the installation spots, it can be divided roughly into the indoor heater and outdoor heater.

1. Indoor tankless water heater

The indoor type is, of course, installed indoor, no matter inside your home or inside your RV. It frees the machine from being damaged by complicated weather outside, but for gas or propane one, installing venting facilities can be a large cost upfront. You can get more information on our best indoor hot water heaters reviews.

2. Outdoor tankless water heater

For outdoor heaters, the ventilation devices are not needed in installation, but you need also to spend much money on getting protection cover to prevent the machine from a long period of bad weather. There are many elements on choosing, installation tips, and best outdoor use types recommendations in our reviews.

best tankless hot water heater reviews
tankless water heater outside


And finally, there is three major power for the instant hot water system that is frequently used in different situations. They are natural gas type, propane type, and electric type. We will make a detailed comparison of the three kinds.

Gas Or Electric Tankless Water Heaters

The gas heater is powered mainly by natural gas or propane, while electric tankless water heater uses electricity, you can easily use it by plugging it into the outlet. Next, we will discuss the difference between the two major types from different aspects as follow:

1. Power

The gas water heater is more powerful compared with electric type, it can support multiple bathrooms and faucets use the same time, thus it is frequently served as a commercial one or whole house type.

While the electric instant heater is less powerful and only supports one single bathroom or even one faucet a time, so it is designed mostly for small studio use or travel one as well as point of use type.

2. Working noise

Because of the special working principle of natural gas tankless water heater, the working noise of most gas types is quite large. But the electric type seldom occurs in the situation. Therefore, if you mind much about the working noise, you may choose an electric type.

3. Energy efficiency

It is tested that natural gas tankless water heater is 3 times more efficient than electric types, over 90% of energy is used without being wasted in the heating process.

4. Price

In terms of price, we do not only refer to the purchasing price but also include the using costs.

On purchasing price, gas tankless hot water is more expensive than electric type because of its large power and high flow rate.

On using costs, electric tankless water does not need venting facilities when installing indoor, and the installation of it is quite simple and straight forward, therefore, it saves a lot of money on upfront costs. While on the other hand, the gas tankless water heater needs ventilation devices for letting out wasted gas, and installation of it is pretty hard, you may need a professional to help you. Both of the installation costs and venting costs are a large sum of money.

However, natural gas heater saves more money in later using costs than the electric type.

5. Environmental friendly

Natural gas is regarded as a clean and green source, therefore, it does little harm to the environment, but it also let out carbon dioxide outside. On the other hand, the electric tankless water heaters do not directly emit greenhouse gas.

6. Maintenance

A heater heats water directly and has little damage to the machine in the heating period, therefore, both of the two types require less maintenance. However, compared with natural gas type, the electric instant machine needs more regular maintenance for safety. And you need to take the maintenance costs into consideration on your budget.

7. Temperature stability

Water temperature rise may be influenced by the cold climates or the altitude of your using spots, when you use it in cold weather or high altitude, the temperature of the electric tankless water heater dropped and so does the flow rate. But to the natural gas tankless hot water heater, it changes less.

In conclusion, the natural gas heater is cheaper in use, powerful, and suitable for those already use a gas or propane line for heating. But the upfront cost is quite high, and you need to install it somewhere airy instead of in the bathroom, the water pressure must be large enough for ignition.

An electric tankless water heater is more affordable and environmentally friendly, but the low power and flow rate determines it hard to be used for the whole house. It can also be a helper for those who plan to install solar panels.

top tankless water heater

Buying Guides

A best hot water heating system can be an excellent helper in your daily life for hot water, not only the quality level, but you should also consider the flow rate, pressure, and all sorts of performances in selecting. Because the living conditions of each family are different, only the most suitable one can be regarded as the best one for you.

Here are some factors you should consider getting the best one:

1. Flow rate

Because there is no tank installed on the heating machine, you do not need to worry about the capacity of it, but still, you need to estimate the amount of water for your daily use. And decide what conditions you are going to use it for, whether it is for commercial use and for large family use. Then you can choose the suitable flow rate to depend on your applications.

For the dishwasher, 1-2.5 gallons per minute of water is needed, and bathroom faucet needs 1.5 GPM, while kitchen faucet ranges between 3-5 GPM. For two-bathroom use the same time in winter or cold areas, you need to get one that reaches at least 6 GPM.

2. Power source

As we have introduced before, there are altogether three types, which include propane tankless water heater, natural gas type, and electric type.

If you need to use it for whole-house use and support two or three showers at the same time, gas and propane tankless hot water can be used, but for small studio or point of use, we suggest electric type for you.

3. Home location

Your home location is also an important factor that needs to consider. If living in the southern part or warm areas, you can choose according to the exact flow rate. Cold weather and climate will have a large effect on temperature rise and flow rate, it may drop 2-3 gpm in cold areas, thus on buying a water heater for cold climate areas, you should consider the factor and choose a relatively high flow rate type.

4. Energy efficient

Gas and propane types are more efficient than electric types especially for a long period of use, thermal efficiency reaches as high as 90% for some types. The electric heater is also able to save 60% energy savings.

For some gas models, there are condensing technology equipped, recovering the unused energy in non-condensing types and greatly improved the efficiency and reduced greenhouse gas emissions.

5. Installation costs

The installation of a tankless hot water system is quite simple and straight forward, but it has a special requirement on pipes, lines, and pressure. If you need to replace a tank water heater with a new tankless one, you may change the entire wire system if it is not compatible with the old one. And for professional installation, you need also to pay a large amount of money. For this, we will discuss it later.

6. Indoor & outdoor installation

Are you still worried that there is no much space at home? Then you can choose an outdoor type. It is able to be installed outdoor and thus needs no venting facilities. But remember to get a protection device for preventing damage from complicated outside weather.

7. Price

Tankless water heater price varies from $200 to $2000, the natural gas type is more expensive than the electric type. For lacking enough budget or gas pipeline, you may choose an electric model or propane model.

Apart from purchasing price, there are also venting costs and using costs you should consider. Natural gas and propane types for indoor installation need venting facilities. Gas types are more costly upfront, while electric is cheaper in installation but costly on later using.

Top 5 Best Tankless Water Heaters

How To Size A Tankless Water Heater

Determining a proper size heating system for your home is a vital step in choosing, if you think buying a large one will solve all the troubles, then you are wrong. On getting an oversize type, you need to hardwire more heating elements and it is really costly and wasteful. On the other hand, buying a too-small one, you may find you need to get a second or even third heater to meet your hot water demand. That would be the last thing you want to occur.

On most occasions, the more water you need, the bigger and more powerful unit you need to get so that enough hot water will be provided in use. But the temperature drops in different climates and weathers.

If living in somewhere warm, you can get a small capacity type because it needs less energy to warm up cold water, a heater with 3-5 GPM can support two showers use the same time easily.

But for cold areas, more energy and pressure are needed in activating the machine. And you should get a large electric or powerful gas models to support multiple showers in a large family.

The following is the chart for the average water temperature in different regions in America:

RegionAverage Groundwater TemperatureTemperature Rise
Northernmost States40° F80° F
Midwestern and Southeastern States50° F70° F
Southern California, the Southwest, and Gulf States60° F60° F
Hawaii and Puerto Rico75° F45° F

You can check out on the official website of the manufacturer for a more close estimate of your temperature in your country. Besides, online calculators and your energy bills are also helpful in deciding your home water use. After making clear of the exact water temperature rise in your area, you can find a suitable one for your home.

Tankless Water Heater Brands

There are now many heater brands on the market, the top-selling and widely praised brands including Takagi, Rheem, Rinnai, EcoSmart, and Noritz.


Takagi heater is normally affordable, and it focuses on producing the best electric products. Flow rate is not so large, perfect for a single room, and small studio use, many of them are portable enough to be used travel or camping use.

For more products detail on Takagi tankless water heater, you can check our reviews.


Rheem is always regarded as one of the best brands, it produces both electric types and gas types. It is quite expensive but is pretty powerful, able to be used as whole-house types, and supports multiple showers at the same time. Constantly water supply frees your trouble of running out of hot water in bathing.

If you intend to know more, please find it in our best Rheem tankless water heater reviews.


Rinnai is a famous brand expert in natural gas and propane kinds, products of it are normally large power and the large flow rate type, able to meet the demand of two or three bathrooms use the same time in any climate. Its top-selling product is RUC98iN Ultra Series. Get more information on Rinnai tankless water heater review.


EcoSmart, as the brand name suggests, dedicates on producing high technological products. Most of its heaters are electric models, flow rates are quite low but are designed compact and small, so you can install them anywhere you want. They can also be a good helper as a solar panel.

If you are interested in the brand, you can get more information on EcoSmart tankless water heater reviews we made for you.


Noritz instant heaters are suitable for middle-sized and small-sized homes, but some of them are also suitable for large family use with their large flow rate and large power. The warranty time is quite long, reaching 12 years on the heating parts, and service attitude are proved to be satisfying. You can check out more product details and price on Noritz tankless water heater reviews.

Apart from the six brands listed above, there are also many other best brands on the market, each has its advantages and shortcomings. You should select based on the working performance and after-sale service attitude.

tankless water heater brands  different brands of tankless water heaters best water heater brand best brand tankless water heater best water heater brand to buy

How We Pick the Best One?

On picking the best one, several steps are made to make it more reliable and trustworthy.

First, we started with the famous brand and top-selling models, read the customers’ reviews and feedback carefully, and then classify the different types of each brand for different applications.
And then according to the types, we compared the selected units from technology, flow rate, energy efficiency and quality levels, service life, etc.

Reliability is also an important factor in our choosing, we checked the warranty time, warranty method, and after-sale service from customers’ feedback and our own test. Some brands with unsatisfying service attitude are abandoned.

You can get more information on our choosing period if you have interested in such an item. In a word, we are not a manufacturer or a seller but only dedicated to recommending the best one for you.

Tankless Water Heater Price

The price varies according to the types and flow rates, normally the larger flow rate or capacity is, the more expensive it will be. Compared with electric types, the natural gas one is more expensive but more powerful, it is widely used for a large family and supports multiple showers use.

For a point of use or portable travel tankless water heaters, the prices are of course much cheaper, but they are designed as flow rate types and unable to support large family use.

Apart from purchasing price, you should also consider the whole using costs. Tankless water heaters can be used for around 10-20 years, the using costs are much more expensive than the machine price itself. Therefore, you should never get a bad quality unit in order to save money, if so, you will need to buy and replace it with a brand new one after several months or even several weeks. Even it can still be used, you need also to get a large sum of money on repairing and maintaining.

Getting an energy-efficient tankless water heater saves a lot of money. Electric types are cheaper in purchasing, but it is more costly for long term use. However, gas or propane models require much money on installing venting facilities and buying all kinds of pipes, but the using costs are pretty low. If you have interested in getting more information on the price, please feel free to check on Amazon.

The Installation Cost

In terms of tankless water heater price, the installation cost is a major concern that you should never neglect. The first is the tankless hot water heater type, for each different kind, including electric, natural gas, and propane, the installation price and process are different.

Electric types are much cheaper than gas models for its straight forward installation requirement. And for the flow rate, each size of heaters may require different installations.

The safest and most reliable way of installing is, of course, finding a professional or an expert to help. And for the installation cost on labor, here are some you need to know:

Firstly, you need to get a permit. Most of the countries or cities require you to get permission for the project and costs around $45-$200 depending on the difficulty and time for the whole installation process. Most installation firms choose to charge according to the hours, it costs about 50 dollars per hour but the price of which is not the same anyway.

If you intend to replace your old tank water heater with a new tankless model, then you also need to uninstall it if the new machine is not compatible with the original system, it costs about $500. For a new home installation, you need to buy the gas or power lines. The whole installation takes about 2 or 3 hours.

  • How about installing a tankless water heater by myself?

While, it is a pretty sensitive task on installing a water heater, for electric types, you need to deal with 220v or 240v power outlet, and for gas types, there needs to be pipelined to be added. The most important thing is the majority of manufacturer warranty works only when a licensed expert installs the unit. If you do it by yourself, the warranty may lose its effect. On account of such situations, we suggest it be installed by experts especially for large flow rate or whole house models.

However, if you do know a lot about plumbing, you can install the point of use or portable types all by yourself, the installation of them is pretty simple and needs fewer tools, but you still need some hours to finish it.

top tankless water heater review
how to install


-For indoor tankless water heater

  1. Install the unit somewhere airy especially for gas or propane one, they should not be installed in the bathroom
  2. Leave a safe distance between the unit and other things in the installation
  3. Install it somewhere that is convenient to operate
  4. Keep the heater dry all the time
  5. Do not put anything on the machine
  6. Always use under instructions
  7. Do not allow a child to operate by himself or herself
  8. Turn it off if you stop using it for a long period of time
  9. Stop using immediately once it operates in unique ways
  10. Check the machine regularly for safety

-For outdoor tankless water heater

  1. Get a protection cover to protect the machine from complicated weather
  2. Do not put an inflammable thing on it


1. Do I need to wait a long time for hot water?

No, one of the features of a hot water heating system is offering instant hot water for you. It heats water and reaches peak temperature almost the time you open up the tap. The only waiting time for hot water is determined by the distance between the heater and using destination. The longer the distance is, the longer it takes for hot water flowing through the pipe.

2. Does a tankless water heater change the way on using the shower?

In order to get the best performance, most manufacturers suggest you use hot water by turning the hot water tap on full and to cool delivered water by opening the cold water tap.

3. Can my heater still work when power is out?

For most of the electric units, water is still allowed to flow even when power is out, but the heating element does not work. If you have a battery backup or other source of electricity, they can still work without power.

4. Are tankless water heater temperature or flow rate impacted by altitude?

Yes, altitude and climate both affect water temperature and flow rate especially for natural gas and propane models. When it arrives 4000 feet, a natural gas heater begins to lose its efficiency at the rate of 4% per 1000 feet. And flow rate drops 2-3 GPM for large flow rate types.

While for the electric tankless water heater, working efficiency is not affected by it.


Tankless water heaters are now becoming more and more popular because of their instant hot water supply performance and compact shape. Especially for the rapid development society, it saves a lot of time for you waiting for hot water in every busy morning.

After reading our reviews, we hope that you have got enough knowledge and got the point of buying the best unit based on your actual needs. If you have any other problems on that, you can ask the manufacturer for help at any time, they will and should always stand for solving all the problems of yours.

Best TypesProducts
Hot Selling TypeRheem RTEX-13
Best One For Middle Sized FamilyEcoSmart ECO 27
Best Large Flow TypeRinnai RUC98iN
Best Whole House TypeTakagi T-KJr2-IN-LP Indoor
Best Energy Efficient TypeNoritz NRC661-DV-NG

And if you want to get more details on other kinds of tankless water heaters, please check out Amazon freely.


David: Penn State-educated Mechanical Engineer and Business-savvy Fluid Dynamics Specialist. Balances family plumbing business support with a thriving engineering career at a top, undisclosed company. (they want it that way) I help Will with plumbing and HVAC needs on his Real Estate.

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