Best Tankless Water Heater (2021) Reviews & Buyer Guide

When you are looking for the best tankless water heater 2021 , keep in mind that they all come with many features and choices. This guide will help you know what to look out for when buying one of the 10 best models on our list from 2021.

Tankless water heaters are the new and improved version of traditional storage tank-type water heaters. The key benefits include instantaneous heating, which means that you no longer run out and have to wait for your hot water when using a shower or washing dishes.

They only use energy when the water is on saving money on energy costs by lowering gas or electricity consumption from production; and fewer plumbing problems since there are no anodes to maintain and replace, which also means less potential contact with bacteria due to standing dirty liquid.

Most of these best tankless water heaters are compact so they are often the best choice in that they are easy to install and can work well, even in small spaces like condos or apartments.

In a Rush and don’t want to read or full review of the best tankless water heaters? 

These are Our Top Tankless Water Heater Choices for 2021

Rinnai V65iN

Rinnai V65IP Tankless Water Heater

  • 9.8 Max GPM
  • 96% Efficiency Rating
  • Gas Powered

Eccotemp i12-LP

Eccotemp i12-LP water heater, 4 GPM, Black

  • 9.8 Max GPM
  • 96% Efficiency Rating
  • Gas Powered

Rheem RTG-95DVLP

Rheem RTG-95DVLP 9.5 GPM Low NOx Indoor Direct Vent Tankless Propane Water Heater

  • 9.5 Max GPM
  • Gas, Whole House
  • 0.94 Energy Factor Rating

Best Tankless Water Heater 2021 Reviews

Best Tankless Water Heater (2021) Energy Efficient

The Best Tankless Water heaters use a highly efficient process that uses less energy than older style storage tank water heaters.

They are the eco-friendly option, and you’ll never have to worry about running out of hot water again!

Features to consider before buying a tankless water heater:

With so many different water heater options available it is easy to be confused about which type of tankless water heater you should choose. Here are some key features that can be helpful in selecting the best water heater for you.

Electric or Gas:

First of all, you need to know whether an electric water heater is best for your home requirements or natural gas water heater.

There are some minor differences between electric water heaters and natural gas water heaters.  Electric water heaters are a little more expensive to run than gas tankless heaters.

The reason is that gas water heaters are more efficient and gas is usually a cheaper energy source, making a gas water heater more economical in the long run than an electric heater. 

Of course, if you don’t have a gas connection in your area a gas heater is not an easy option for you, not impossible though, as you may be able to connect to bottled gas.

A big benefit to electric water heaters is they don’t need any ventilation, so they can be installed internally without an exhaust.

In short, we can say there are advantages and disadvantages to both gas and electric water heaters. It’s up to you, what are your house requirements. So, decide accordingly.

What Flow Rate Do You Need?

The second thing which you need to think about before choosing a tankless water heater is the hot water flow rate needed. Flow rate can be measured in gallons per minute, or GPM, with each fixture. Your needs will depend on how many people are in your house and the different uses of hot water in your house.

If you are unsure of what size you need, use the following as a guide to the needed flow rate for your tankless water heater.

A family of more than 4 adults should go for a water heater with a potential flow rate of 8GPM to 10GPM. If you are less than 4 people you can go for something as low as 3GPM to 5GPM flow rate. GPM is the number to look for that refers to the gallons-per-minute a water heater can produce.

The average shower has a water flow rate of 2.1 gallons per minute

Be aware that some High flow Gas Heaters may need an upgrade to the pipes to achieve the correct flow rate for them to operate efficiently. 

Upfront Cost V’s Ongoing Value Of a Tankless Water Heater

A good tankless water heater is not a small investment and will cost anywhere between a couple of hundred dollars to over $1,000 but if you choose the right unit, it will last you up to 20 years, maybe more.

So, a little more upfront expense can be a wise choice in this case, if it means a quality heater unit that will last a long time. Of course,  it also depends on the requirement of your house and your budget.

But what is the best tankless water heater for you?

Tankless Water Heaters Are Great Value

Tankless water heaters are the best value because they only heat water when it is needed. Providing hot water immediately, shutting down saving energy when not in need! Over time this can save you thousands of dollars on your energy bills.

If you’re looking for a tankless water heater, look no further. We’ve compiled the best tankless heaters in one place to help guide your decision-making process!


Rinnai V65iN High-Efficiency Tankless Hot Water Heater

  • 9.8 Max GPM
  • 96% Efficiency Rating
  • Gas Powered
Eccotemp i12-LP water heater, 4 GPM, Black

  • 9.8 Max GPM
  • 96% Efficiency Rating
  • Gas Powered
Rheem 240V Heating Chamber RTEX-13

  • 8.4 Max GPM
  • 82% Efficiency Rating
  • Gas Powered
Stiebel Eltron Tankless Water Heater

Stiebel Eltron Tempra Plus 24
  • 4.0 Max GPM
  • 99% Efficiency Rating
  • Electric Powered
Rinnai RL Series HE+ Tankless Hot Water Heater

  • 7.5 GPM
  • 0.82 Energy Factor Rating
  • Gas, Outdoor
Camplux 5L 1.32 GPM Outdoor Portable Propane

  • 1.32 Max GPM
  • 99% Efficiency Rating
  • Outdoor Portable
Best Tankless Water Heater (2021) Energy Efficient

  • Max GPM 6.6
  • 0.83 Energy Factor Rating
  • Natural Gas, Indoor
Stiebel Eltron 233219 2.5 gallon, 1300W, 120V SHC 2.5 Mini-Tank Electric Water Heater

  • 2.5 Max GPM
  • 99% Efficiency Rating
  • Electric Powered
Rheem RTG-95DVLP 9.5 GPM Low NOx Indoor Direct Vent Tankless Propane Water Heater

  • 9.5 Max GPM
  • Gas, Whole House
  • 0.94 Energy Factor Rating
Marey Power Gas 10L 2.7 GPM Natural Gas Digital Panel Tankless Water Heater

  • 3.1 GPM
  • Gas, Point of Use
  • 54-87% Energy Efficiency

1: Rinnai V65iN High-Efficiency Natural Gas

Rinnai V65iN High-Efficiency

The V65iN is the perfect economical combination of high efficiency, comfort, and value in a tankless water and natural gas heater from Rinnai. This model is ideal for small to medium-sized homes or herbs, compact, easy to install, reliable, and suitable for interior areas; Rinnai products provide peace of mind with a warranty that exceeds the competition.

Endless Hot Water

As well you can also choose between taking a hot tub shower, doing a laundry service, or using a shower. Rinnai’s heater will never run out of hot water leaving you cold.

Rinnai heater is hot water with ThermaCirc360 technology that circulates hot water through your pipes to get hot water faster.

Save Valuable Space

Furthermore, your water heater shouldn’t be a behemoth! The compact design allows installation in non-traditional areas such as an attic, crawl space, or blanket. Save 16 sq. M. space is a Rinnai heater waterless tank only the size of a small suitcase.

Affordable and Efficient Saving

The efficiency included in the design of the tank means cutting out CO2 emissions (compared to the tanks), using less energy, and saving water. Use 40% less energy than traditional tanks because you only heat water when you need it.

100 Years of Confidence

This model is available in the market with 100 years of confidential experience. Rely on # 1 to sell wireless electricity in North America for all your heating needs. For technological advancements such as WiFi monitoring, your trusted Rinnai service provider can check the efficiency of your tankless water heater and face problems before getting a break from work.

Sustainable Reliability

It is a wise investment now and in the future when you combine stability and resilience. All parts of the Rinnai Tankless water heater are repurposed so that the parts can be easily replaced by buying a whole new system. The average life expectancy is 20 years vs. 8-10 per traditional tank. With a premium product, you will save – money and worry – over time.

  • Easy to install
  • Dependable Tankless unit
  • Take about 30 seconds
  • Temperature control
  • Bit Expensive

2: Eccotemp i12-LP water heater, 4 GPM, Black (Best Overall)

Eccotemp i12-LP water heater, 4 GPM, Black

The Eccotemp 12 Liquid Propane 3 GPM Tankless Water heater has innovative revolutionary features, value making it unlike any other waterproof heater on the market today. So, this model is ideal for vacation cabinets, kitchen sinks, and house use. The i12 only pumps at 2 watts while at idle and 1.07 Amps at runtime, making it a very efficient electric motor.

Modern Design And Efficient in working

it’s a sleek and modern design that is different from the other heaters and makes it more beautiful in shape than the other ones.

Efficient in working

Accordingly, this model is also working very efficiently and always shows good results during the heating of water and other timber material in different stages. The glass panel is set in front of this model, which makes it work more powerfully in dual side functions.

Liquid Propane Powered

The Eccotemp 12-LP has powered liquid propane and an internal model designed for the production of mid-range hot water where you need a lot of warm water at the same time.

The model also provides an increase in temperatures of 35-40 Fahrenheit when operating at a flow rate of 4 GPM and an increase of 78-degree Fahrenheit temperature at 1.5 GPM.

Overall Performance

The overall performance of this model is always pleased and good enough to work very accurately. The steel vent kit is included in this model which is stainless. As usual, the overall performance is efficient. Nevertheless, an excellent and huge power motor is beneficial for working. The performance is also good and secure enough in this model is due to the right bag setting for dusting in the dust during work and collects in the right way for more work.

  • Solid heater
  • Sleek and works great
  • Decent look
  • Propane on-demand hot water
  • Digital temperature control
  • No extension

3: Rheem 240V Heating Chamber RTEX-13 Residential Water Heater

Rheem 240V Heating Chamber RTEX-13 Residential

Rheem has been manufacturing the best domestic tools, but this one is far more special than its previous products, which is durable and easy to use. This model is Durable Copper dual-sink ignition, Serviceable, Self-modulating temperature control.

LED Display

240V model of Rheem has a digital temperature control system with the display of LED (+/1 degree accuracy). This model also included 99.8% energy efficiency. Exterior controls for adjusting the temperature at elevations of 1 ° f. Head of Water-Saver Shower – 1.5 GPM.

Easy to Install and use

Furnished for easy replacement, easy installation, and digital heat display 54 A. 13kW Model Flow Rate: up to 3.17 GPM. Rheem gives durable copper two-way heating element and serviceable. Self-modulating control field and simple installation – 1/2 NPT adapters included; side 1/2 inch Connected water connection.

Lightweight Design

Rheem has set the new model of the best tankless water heater 2021, which is excellent, lightweight, and most sturdy in the shape and design. The 240V is portable and very light in weight for shifting it from places in different range zones. The sliding and heating adaptability in the model of water heater is so helpful for ease to use.

  • Greats work
  • Replace with better flow
  • Heats faster
  • Digital control panel
  • Economical

4: Stiebel Eltron Tankless Water Heater (Heavy Duty-Overall)

Stiebel Eltron Tankless Water Heater

The Stiebel Eltron has set the new model of Tempra 24 plus with excellent and accurate heating settings in the heater. This model is ideal for hair salons, kitchen sinks, and house use. Good German technology is also used in the water heater for different heating brackets in the glass materials.

Continuously Flow

The advanced German Flow patented technology, developed by Stebel Eltron, keeps itself at constant water temperatures for maximum comfort. It will reduce the flow less if the demand for hot water exceeds the capacity. Hot summers will never be interrupted again.

Space and Energy Saver

Its sleek, minimalist design saves space yet providing endless hot water for your entire home, and no access is needed. The Eco-friendly unit saves energy through auto-modulation and the ability to measure electric flow. Increased savings also show how much you save on energy costs.

Easy Operation

The electronic flow sensor is switching to a heated indoor heating system. It’s audio while in use and there’s a digital heat display and temperature memory buttons set.

Warranty Included

The Stiebel Eltron is rated higher than the standard wireless water heater that produces the highest levels of comfort and reliability. Our 7-year warranties and 3-year warranties are included with the purchase.

  • Worth every penny
  • Lightweight
  • Mounting installers
  • Pre-Set temperature buttons
  • Not returnable

5: Rinnai RL Series HE+ Tankless Hot Water (Efficient for work)

Rinnai RL Series HE+

The R75LSe delivers about 7.5 liters of hot water per minute (GPM), making it ideal for two to three bathrooms. Easy to install on any exterior wall, the R75LSe freezes the interior space and saves on installation and construction costs.

Circ-Logic Technology

Circ-Logic technology allows you to set repetition patterns to suit your regular habits. Hot water is available when you need it! In this model, the Valve kit is included and the killer feature of the Rinnai RL series is that it gets instant hot water on demand and with a built-in re-circulating pump.

High Efficiency

Enjoy the endless supply of hot water with this top-notch use of Rinnai’s waterproof tank spray. Only the smallest suitcase size, the RL75eP is compact, easy to install, reliable, and suitable for outdoor environments. Rinnai products provide peace of mind with warranties that exceed the competition.

Impressive Quality

This model is impressed by the quality of construction and by the inclusion of isolation valves and pressure relief valve in the kit. For some models, you will need to install an additional reuse pump but the Rinnai Series hot water model it is readily available for showers, sinks, and kitchen appliances such as washing machines or one bathroom because the pump is built into the tank.

Easy to Install

This model is easy to use everywhere. You can press a button on the side, or use a motion detector, or a timer, or an app (Rinnai has many options) and as you enter the main toilet, cold water circulates in the tank and you get heat water right there. The good thing here is that you can never drain that water, back to the cold climate.

  • Built-in recirculation system, no “cold water sandwich” problem
  • A digital controller that allows to schedule the recirculation to align with usage patterns
  • Multiple venting options
  • Can be used with or without a dedicated recirculation line
  • Less draining water
  • Bit pricey

6: Camplux 5L 1.32 GPM Outdoor Portable (Long-lasting Water Heater 2021)

Camplux 5L 1.32 GPM Outdoor Portable Propane

CSA has authorized a waterproof heater for the US and Canadian markets. Very low water pressure is just beginning to require 3.0 PSI! It also works well with the Camplux 12V 1.2GPM fuel pump.

Low Water and Gas Pressure Required

It only requires 2.5 PSI of water pressure to work. Once open, there will be an endless supply of hot water and you can enjoy hot water at any time on the go. The quality gas pressure used is 0.4PSI with a maximum output power of 28,000btu / hour.

A gas water heater cannot be used for drinking water. The propane water heater line for camplux without the recommended lift is over 2000 ft.

High Quality

It weighs in and operates at 1.32 liters of hot water per minute. Due to its cheap price and high-quality inexpensive operation, it is considered a great value to recommend a waterproof camper heater or travel trailer. It is also the oldest retail store in the market for several years.

Anti frozen protection

With an external installation, it can meet the condition under a zero temperature. When the unit experiences a low temperature, the ice protection system works and takes precautions on time.

Corrosion resistance to internal materials

It is fitted with a stainless steel burner and a copper water tank, both of which are highly resistant to corrosion. The burner has 2 D cell batteries so it makes it ideal for off-grid or other areas where electricity is not readily available.

  • Compact shape, wonderful for camping shower
  • Two buttons settings for water temperature adjustment
  • Endless hot water supply
  • Light-weighted
  • Unbeatable cheap price
  • Temperature control with gas and water flow

7: Takagi T-H3-DV-N-Condensing Indoor  (Best Budget Water Heater)

Best Tankless Water Heater (2021) Energy Efficient

Another Japanese waterproof heater, the Takagi T-KJr2 is more expensive than most gas models but offers the same quality. This model is available in the market at a low price which is under 1000 $.

To buy this product connects with Amazon and other sellers that are related to this company.

Endless Hot Water

You can also choose between taking a hot tub shower, doing a laundry service, or using a shower. Takagi’s heater will never run out of hot water leaving you cold.

Takagi heater is hot water with ThermaCirc360 technology that circulates hot water through your pipes to get hot water faster.

Overall Performance

The overall performance of this model is always pleased and good enough to work very accurately. The steel vent kit is included in this model which is stainless. As usual, the overall performance is efficient. Nevertheless, an excellent and huge power motor is beneficial for working. The performance is also good and secure enough in this model is due to the right bag setting for dusting in the dust during work and collects in the right way for more work.

Easy to Install

With the installation of 199,000 BTU gas, the T-H3-DV-N can produce enough water for four bathrooms in warm climates or three baths in very cold conditions. Computer security features, No driver light to worry about. It satisfies the 2012 SCAQMD Rule 1146.2 Ultra-Low NOx Emissions.

  • Available in low cost
  • Easy to use
  • Temperature control
  • Honestly good performance
  • Low flow rate
  • Mid-efficiency

8: Stiebel Eltron 233219  (Best Performance)

Stiebel Eltron 233219 2.5 gallon, 1300W, 120V SHC 2.5 Mini-Tank

The smaller Stebel Eltron SHC tanks are manufactured in Germany. They are designed to put hot water where you need it to be used quickly, smoothly, and save water. European, attractive design includes any decorations to be revealed to look or be hidden under the kitchen.

Coupled with cold water and used as hot water traveling alone, or mixed with hot water from a remote tank such as a buffer tank to reduce delays, SHC always releases hot water when needed.

Easy installation plus saves water and electricity

All three popular sizes are simply connected to a standard 120-volt outlet for easy installation. By placing hot water in use, the flow of the pipes is reduced and the use of water and power is reduced.

A small tank with its obvious landfills and low loss of industry saves you money all day, every day by reducing energy needs.

Convenient temperature adjustment

A simple thermostat dial is easily accessible from the top to adjust the temperature from 86-140 ° F. A special snow protection setting can be selected to keep the tank temperature above freezing.

Combination of Hot and Cold Water

The SHC mini-tank frees up valuable space while providing plenty of hot water for hand washing or kitchen use. Coupled with cold water and used as the only supply of hot water, or hot water pipes from a remote tank to reduce delays, SHC always releases hot water when needed.

Suitable for Commercial and Residential Use

The Stiebel Eltron SHC mini-tank water heater is ideal for office buildings, shops, supermarkets, truck stops, food trucks, restaurants, petrol stations, schools, hotels/cars, and retail, industrial and institutional.

SHC is also a perfect model for Laundromat, in baths for a Jacuzzi tub, kitchen sinks, cabinets/toilets, basement showers, and showers. A comparison of commercial and residential use shows that this model is essential for both sectors.

  • Relatively low price
  • No venting
  • Automatic control
  • Not make a noise
  • Available in small size
  • Performs worse and consumes more energy in northern climates

9: Rheem RTG-95DVLP (Best Portable)

Rheem RTG-95DVLP 9.5 GPM Low NOx Indoor Direct Vent Tankless Propane Water Heater

Rheem RTG-95DVLP Direct Vent Indoor Propane Waterproof Tank Water Tanks – this model provides you with the right solution for heating your home water. Imagine never running out of hot water again.

Lightweight Design

Rheem has set the new model of the best tankless water heater 2021, which is excellent, lightweight, and most sturdy in shape and design. This model is portable and very light in weight for shifting it from places in different range zones.

Continuous Supply

Rheem provides you with innovative, wireless products that provide a continuous supply of hot water from efficient units and space-saving applications. This model is easy to replace a 75-gallon heater and it’s easy to repair anywhere.

Rheem Brand More Models Check Now 

Direct Vent System

This model has some specifications that are 9.5 gals ./min. at 35A-Degree F climb max. – 7.4 gal./min. at 45A-Degree F increases max. New features are 3-Inch / 5-Inch Direct Vent System with consensual condensate collector which connects to metal Fab Inc., 3-Inch / 5-Inch Concentric Venting without an adapter.

Generation Burner Technology

Generation Burner Technology is 26 GPM Minimum Flow Rate and 40 GPM Minimum Flow Rate at the industry level.

This model also has a UMC-117 remote control and 10 ft of thermostat wire included with the EZ-Link cable is available for high throughput applications to connect two wireless units to operate as one.

  • Endless and consistent supply of hot water
  • Vent system designed for PVC pipes
  • Compact sizes
  • Easy to use
  • Easy to install
  • Noise is a common problem

10: Marey Power Gas 10L (Best Powerful)

Marey Power Gas 10L 2.7 GPM Natural Gas

This compact model saves space and allows for easy installation almost anywhere. It fires lowes water volume as needed and allows you to control the flow of water and gas flow at better temperatures.

High Altitude

Gas-free water heaters are less efficient at higher temperatures. As a rule of thumb for any altitude 4000 ft high, a gas tank unit will lose 4% of its BTU at every 1,000 ft above that altitude. Electric units are not affected at high altitudes.

Save Water

It saves 60% more water and less electricity than a conventional water heater, making it more expensive. Only gas is used when the water is flowing. This model has a cleaning kit that cleans the internal save water.

Compact Design

The design on the computer saves space and allows for easy installation in almost any location. There is no use of electricity (works with 2 D Cell batteries). To get the hot water immediately then use this model of best tankless water heater 2021. This model is also great for DIY.

Marey Power is used for hydronic heat which is suitable for hot water. So if you’re in hurry and looking for a hot water grade, this is the product for you! It is also a good alternative to those homes that suffer from power outages because the heater does not need electricity.

  • Digital temperature display
  • Great for DIY
  • Provide constant airstream
  • Lightweight
  • Fire hazard

11. Rinnai RUR98iN (Best For High Flow Situations)

Ideal for a large family, the Rinnai RUR98iN is capable of supplying constant hot water to multiple locations at the same time with very little pressure drop. Imagine being able to have your dishwasher, washing machine, and a few showers going at the same time, no more arguments because someone turned the hot water on while you were in the shower. 

The technology in this unit is impressive, recirculating, super-insulated with double heat exchangers, this innovative design gives an endless supply of hot water and unparalleled efficiency too. Achieving an energy factor of .96, in simple terms, almost all of the heat energy is transferred to the water, very little is wasted. Lowering energy bills and reducing your carbon footprint.

It is also a surprisingly compact design that can be fixed anywhere in the house if it is connected to exhaust. The best thing is that it can be monitored with WIFI as well. Absolutely, this is one of the best water heaters for use.

Flow rate:

The Rinnai RUR98iN has a high flow rate 9.8 gallons per minute, which is why it is perfect for a large household, and what we really like about this unit, is it can be installed using 1/2 inch pipes.

Other features:

Rinnai has made this unitto last, built from stainless steel, and comes with a 12-year warranty on the heat exchanger.

It also has a condensing unit with dual heat exchangers and a recirculation pump. This basically means your hot water is pretty much instantaneous to the outlet with the Rinnai RUR98iN. There is a pump inside and a device that helps the cold water from your pipes come back to the heater. So you will always have hot water, on demand!


The size of the Rinnai water heater is 12.5 inches wide x 10 inches deep x 26 inches tall, think the size of a small carry on suitcase.

After a lot of research and testing, we have found that this is the best tankless hot water system. It has a high flow rate and efficiency, which means it will last for years without any problems. This makes it worth the investment!.
  • High flow rate GPM- 9.8
  • Instant hot water system
  • Equipped with WiFi monitoring and control
  • Fast temperature rise
  • Solid warranty and aftercare
  • Premium Price Point
  • Overkill for small homes

12. Rinnai RUC98iN Ultra Series

Rinnai RUC98iN

The RUC98IN by Rinnai is a gas-controlled tankless water heater that comes outfitted with an advanced control front panel. And as you would expect this is in no way different in quality from and has all the advantages you can expect from Rinnai. It is also WiFi-enabled for monitoring and changing settings.

Flow rate:

The flow rate of the Rinnai RUC98iN Ultra Series (indoor) is 9.8 gallons per minute. It has Up to 0.96 Energy factor and Up to 0.92 Uniform Energy factors with 199,000 max BTU.

Other features:

It has a compact design which is even suitable for both big and small houses. Rinnai also takes tankless water heating one step further with condensing technology that delivers more efficiency than ever before.


It has a space-saving ultra size design with twin pipe which allows Indoor Installation. The complete measurement size of this product is Width: 18.5″ Height: 26″ Depth: 10″ Weight: 61.7 lbs

You may need to upgrade your feed pipes as this unit requires a 3/4″ Gas Connection & Water Connection to function properly.

This is a model that is designed to use indoors with natural gas.
  • Powerful
  • Energy saving
  • 9.8 GPM of flow rate
  • Suitable for indoor use
  • Expensive

13. Rheem RTG-84XLN 8.4 GPM Low NOx (outdoor):

Rheem RTG-84XLN

Rheem is a company that provides you with all innovative, new tankless products. Rheem RTG-84XLN, is an outdoor and natural gas Residential Tankless Water Heater. This great little unit provides a continuous supply of hot water from an energy efficient and space saving units.

Flow rate:

RTG-84XLN maintains a flow rate of 8.4 gallons per minute when working on a 35-Degree water temperature rise.

Other features:

A small but unique feature of the Rheem RTG-84XLN 8.4 GPM Tankless Natural Gas Water Heater is that it comes with a remote control so you can adjust the output water temperature from anywhere in your home easily.


The Rheem RTG-84XLN features a compact design for installation in small areas. Measuring just 8.88 inches deep x 13.88 inches wide x 23.63 inches high.

Afterward, it has a structure of self-modulation which is to maintain a consistent outgoing water temperature.
  • Low in cost
  • Remote controller
  • No venting required
  • High flow rate- 8.4 GPM
  • Water saving
  • Anti freeze protection
  • Only suitable for outdoor use
  • Hot water is not instant

14. Rheem RTGH-95XLN Prestige Natural Gas

Rheem RTGH-95XLN

Indeed, when you think of tankless water heaters for outside use, Rheem water heaters will always be one of the top 3 recognized brands. Their quality and customer service has earned them this reputation.

The Rheem RTGH-95XLN Prestige series are an extremely versatile option. They can operate with very low water flow, and will tolerate extremes in temperatures well too.

Flow rate:

This is a high-capacity tankless water heater. It offers 9.5 gallons per minute making it an excellent option for big homes, and can easily supply hot water to multiple bathrooms at the one time. The Prestige series Tankless Water heaters will also operate at very low water flow rates too, as low as 0.26GPM. So, even if you are just trickling hot water while having a shave, this unit will not drop out and give you any unexpected cold water bursts.

Other features:

This water heater is made by Rheem, a brand known for its top quality. Being an outdoor unit there is no need for ventilation. It has a .94 Energy Factor with a long-lasting stainless steel condensing heat exchanger. Besides, The Rheem RTGH-95XLN is made of stainless steel and the innovative Rheem Guardian Overheat Film Wrap prevents the unit from overheating.


This is considered an energy-saving and compact item. 27.5 x 9.75 x 28.5 inches in total. Its space-saving design is perfect for all types of houses.

Rheem is the business chief for absolute warming, cooling, and water warming arrangements.
  • Energy efficient
  • Noneed for ventilation
  • Suitable for rainy climate
  • Excellent unit of good size
  • Low temperature rise

15. Takagi T-KJr2-IN-NG Indoor Tankless Water Heater, Natural Gas:

Takagi T-KJr2-IN-NG

The T-KJr2-IN-NG Indoor Tankless Water Heaters is a fully modulating gas-fired tankless water heater designed to produce enough hot water for two locations in the house at once. Making it the perfect choice for small to medium-sized homes or buildings where space and efficiency are key.

Flow rate:

The Takagi TKJr2-IN NG indoor tankless water heater can produce enough hot water for up to two bathrooms in warmer locations. It can produce up to 6.6 gallons of hot water per minute.

Other features:

This water heater features copper heat exchangers, which are more efficient than stainless steel but they don’t last as long.


This Takagi is pretty typical in size to other tankless water heaters, measuring 20.25 inches x 13.75 inches x 7.75 inches

The T-KJr2 model is the baby unit in the Takagi line-up. The T-KJr2 is ideal for light private use.
  • Low in cost
  • Easy to install
  • Lower flow rate/GPM than other gas units

16. Stiebel Eltron Tankless Water Heater – Tempra 24 Plus (Electric):

Stiebel Eltron

As far as electric tankless water heaters go, the German made Tempra 24 Plus is surprisingly good and maintains water temperature for constant comfort. It features advanced flow control technology to control the flow of water if more hot water is needed. Making them very energy efficient, but just as important, hot then cold showers will be a thing of the past.

Stiebel Eltron’s top-rated electric tankless water heaters perform to the highest standards for comfort and reliability. Furthermore, it is almost silent and features a digital temperature display.

Flow rate:

It has a GPM of 4.0, which is decent for an electric instant water heater. Besides, all the uses This heater has a high-temperature rise of 43 degrees Fahrenheit along with 99 percent energy efficiency.

Other features:

This amazing item is best for the whole house, and no venting is required. With an energy efficiency rating of 99 it will save you money. It comes with a 7-Year Leakage and 3-Year Parts Warranty.


It has a small, sleek white design that saves space yet still provides endless hot water to the whole house.

This German product tankless water heater is a Progressed flow control licensed innovation created by Stiebel Eltron.
  • Good design
  • Flawless unit
  • Digital control
  • 4 GPM flow rate
  • Expensive for electric unit

17. Eemax EEM24027 Electric Tankless Water Heater

Eemax EEM24027

You more than likely have never heard of Eemax, but they have been making some of the best electric water heaters for over 25 years. They pride themselves on being the absolute best, featuring innovations such as a copper and brass replaceable heat exchanger unit.

Flow rate:

This water heater can manage to maintain a flow rate of 7 Gallons per Minute. Moreover, It also can produce enough hot water for up to 1 shower and 2 sinks simultaneously in colder climates.

Other features:

These units are cheap to run and achieve an almost perfect energy rating of 99.8. In hotter atmospheres, it can create enough high-temperature water for up to 4 Showers or sinks all the while maintaining good water pressure.


Eemax definitely has a compact size 17 inches in height x 17 inches wide x 3.75 deep saving valuable storage space when installed in a closet. Although compact the EEM24027 is capable of supplying all your hot water needs in a house.

  • Very efficient water heater
  • Emphasis on energy efficiency
  • Quick and painless installation
  • For small homes only

18. EcoSmart ECO 27 Electric Tankless Water Heater

EcoSmart ECO 27

Eco-Smart items are innovatively best in class and are utilized around the world. And these tankless electric water heaters are super easy. In fact, every EcoSmart tankless electric water heater produces endless hot water. While, at the same time it saves space, time, and money. It also allows us to reduce our overall energy and water use.

Flow rate:

Eco smart will activate with a flow as low as 0.3 GPM. It just heats up the water as it passes through the unit. Hence, Instead of storing hot water like a traditional tank water heater, its self-modulating technology gives water at the required time.

Other features:

EcoSmart ECO 27 is a tankless electric water heater that is ideal for providing hot water for apartments, condominiums, townhomes, and other whole houses. Even, it really saves time with its point-of-use, installation and on-demand heating cut down on waiting for hot water.


Conventionally, all tankless heaters occupy a great deal of room, yet EcoSmart’s smooth, divider mounted plan opens up floor space for more stockpiling and is 90% smaller than a tank.

  • Reasonable price
  • Unmatched quality
  • Lifetime warranty
  • Conversion option to Boiler Mode
  • Warranty requires professional installation

19. Sio Green IR288 v2 POU Infrared Electric Tankless Water Heater – None Corrosion – Extends The Life of Tankless Water Heaters:

Sio Green IR288 v2 POU Infrared

The Sio Green is different from other tankless water heaters because it uses infrared technology to heat the water, this gives them an exceptional life span with no ongoing maintenance needed. This is a premium little unit that will surprise you with how efficient it is.

Flow rate:

Sio Green IR288 has a GPM of just 1.7. Of flow rate. This is a really ideal flow rate for home installation. Furthermore, this is also a space-saving and ultra-practical tankless water heater system.

Other features:

This electric tankless heated water storage has an activated Power Technology. Its Manual Mode can also undoubtedly tailor its presentation to your family’s needs.


The ergonomic size and simple yet innovative construction will allow you to install it almost anywhere or use it as a booster. The manufacut=rer reports the dimensions as being 17.3 inches high x 11 inches wide x 3 inches deep.

This is really the smallest tankless water heater on the list. But it still has a high energy rating of 98 percent.
  • Easy to install
  • Impressive quality
  • Low flow rate

20. Rheem RTEX-18 18kW 240V Electric Tankless Water Heater:

Rheem RTEX-18

With durable twin copper immersion elements, the Rheem RTEX-18 18kW 240V Electric Tankless Water Heater produces no sounds at all so it can be installed it anywhere in the home. The power of this water heater is adjustable just to avoid wasting energy. In this way, you will have your own control on the energy of the water heater at your home.

Flow rate:

The flow rate of this smallest and amazing product is up to 4.4 GPM which means 7 gallons per minute. .it also has an easy replacement, simple installation, and digital temperature display as well.

Other features:

The features an electronic control allows for temperature adjustment in one-degree increments from 80 degrees to 140 degrees (F).


it is really small in size. Users can easily get the benefits of this product.

Rheem-18 is one of the top electric divider mounted boiling water warmers. You can likewise leave the radiator to utilize self-tweak and spare temperature.
  • Not noisy
  • Best in quality
  • Efficient rating
  • Self-modulating technology
  • Low flow rate

Things You Need To Look Before (Review and Buying Guide)

tankless water heater buyer guide

The continuous flow of hot water from every tap in every home right now is one of the most important things for all homeowners. For many people, having a large tank in which to heat water underground can be frustrating as it takes up more space and consumes many resources that can be saved and used. In some places, people use a boiler combo water heater.

There are some factors that you need to consider before you decide to buy the tankless water heater for your domestic work

 Selecting the Energy Savings / Efficiency 

Since power saving is one of the main benefits of switching to a water heater, it is a factor that you should take great care in choosing the right unit to meet your needs. One thing to review in mind is that the efficiency and cost of the utility system are decreasing as the demand for hot water in houses increases.

 Power Saver/ Efficiency 

But even so, you would expect that Minnesota would outsource the traditional water heater to a power reserve. Water slides are one of many machines that use an Energy Factor (EF) rating to measure wing performance.

 Select the Proper Size to Meet Your Needs 

Manufacturers measure their units by determining the temperature increase required to achieve a specific flow rate. When calculating these two features for your family, you will be able to choose a waterproof heater system that can meet your family’s hot water needs.

 Flow Rate 

As a general rule, you can expect your water heater to deliver within 2 to 5 liters (flow rate) of hot water per minute. On consumer reports gas systems, tend to produce higher flow rates than electrical systems in the world.

 Select the fuel energyType for your Tankless Water Heater​ 

The most common options are natural gas, propane, and electricity. Usually, the type of fuel you choose will be determined by the fuel available locally. If you are lucky enough to have a choice, you should compare each fuel for the money and the efficiency of the tank unit before making your decision.

 Size and Efficiency 

This is a critical decision, since the type of fuel you choose will affect the size and efficiency of your wing, and will ultimately determine your annual operating costs. Changing fuel sources can be a huge expense, so this is worth the decision if you chose a new home.

What Size Tankless Water Heater Do I Need?


Money can buy the main source of heating systems. The entry requirements are different from the traditional best tankless water heater 2021 . However, there is more flexibility when removing a wireless unit because the vents can penetrate the roof or directly to the sidewall, but this also makes power penetration more difficult.

 Maintenance of Tankless Water heater 

If the annual maintenance work is not done on a traditional water heater, the water stored inside the tank will eventually destroy the unit by not eating the tank until it leaks. The only solution when this happens is a new water heater.

A tankless water filter will not leave a huge hole in the water if you fail to do repair work every year, but it can send an error code that prevents the unit from getting warm at all.

 Hard Water 

Hard water is the first enemy of an on-demand electrical generator. All water contains minerals such as calcium and magnesium and the highest concentration of these minerals, the “hard” water. Different areas have different levels of hardness, but the more minerals in the water the faster the mineral will build up within a hectare.

Frequently Asked Questions ( FAQs )

1: What is a tankless water heater?

Most North Americans currently use a heater tank for storing hot water in their homes. A water heath tank keeps water heated 24 hours a day, whether you’re at work or sleeping. A waterproof heater, on the other hand, does not store hot water. It burns the water the way you use it.

2: How can the best tankless water heater heat water instantly?

When you open the soup, the flow of water causes the heater to open. Whether you use gas or electricity, powerful electric heaters or appliances will turn on, heating water faster as it passes through the unit.

The water is heated immediately, and the time it takes to get hot water is directly related to the distance from which the hot water has to evacuate the water heater. Heaters or objects then turn off when you turn off the hot water. The energy consumed is only for the hot water used.

3: What If I live in an area with high altitudes?

Gas-free best tankless water heaters 2021 are less efficient at higher temperatures. As a rule of thumb for any altitude 4000 ft high, a gas tank unit will lose 4% of its BTU at every 1,000 ft above that altitude. Electric units are not affected at high altitudes.

4: Is this a new technology?

No. Europe, Asia, and South America, where energy costs are more expensive than in North America, have been using unmanned water heaters for 75 years. Bosch Water Heating has been selling and supporting tankless water heaters in the United States since 1979. However, most Americans are now learning this technology and its benefits. Japanese are also learning about this technology.

Final Words

You went through the top selection of tankless water heater 2021 on the market. Hopefully, you can find a reliable and powerful product that can provide enough heat to your tank and will last for many years.

You can see a more detailed breakdown of our tankless water heater cost guide.

To summarize, if you need a cheap heater, I would recommend the Rinnai V65i. It has the latest quality, long-lasting performance, and long warranty and is widely used by heater growers. By using this guideline selection is very easy for me, which water heater is on sale and easy for a travel trailer.

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