🥇 Best Tankless Water Heater Reviews of 2021

If you’ve ever had to wait for hot water, you must understand just how frustrating it can be.

Tankless water heaters are the solution to your frustration. These units will not only give you direct access to hot water but they also help you save on your utility bills by up to 40 percent.

After 100 hours of research by our team, we have found the best tankless water heaters for you. Let’s dive in.

Rinnai RUC98iN – Our Top Pick

The Rinnai RUC98iN has a high thermal efficiency set at 96 percent. It can produce up to 199,000 BTUs and its overall design allows for easy installation. This unit also comes with multiple venting options and it uses either propane or natural gas.  

Best Tankless Water Heater Reviews of 2021

1. Rinnai RUC98iN – Best Tankless Gas Water Heater

Best Tankless Water Heater

There is a good reason why the Rinnai RUC98iN comes highly recommended. It has a durable and stylish build quality that is easy to install plus it produces enough heat for two showers running at the same time.


The Rinnai RUC98iN features a space-saving design that enables easy indoor installation. It’s a quiet unit according to user reviews. It’s also energy efficient at 96 percent thermal efficiency when on natural gas as well as propane. You can use it both in residential as well as commercial settings. However, you will need to buy a temperature range commercial controller separately if you plan to use it in a commercial setting.


Most users found this unit easy to install. With a maximum of 199,000 BTUs, this unit will achieve constant temperature levels even if you have multiple faucets running at the same time. When it comes to maintenance, the unit comes built-in isolation valves that allow a mineral dissolving solution to clean the system without the need to remove any of the pipes.  The unit also features an automatic scale detection that keeps the unit from failing while increasing its overall durability. In the case of a power surge, this unit comes with a built-in chip built prevents short-circuiting in order to keep your home safe. The Rinnai RUC98iN is designed to meet California and Texas Nox Emissions standards. It also comes with a variety of venting options and you can even vent it through the wall if you want to.


  • Remarkable energy efficiency
  • Installation is easy and straightforward
  • Consistent and reliable heating performance
  • A variety of venting options


  • The temperature range commercial controller is bought separately

2. Stiebel Eltron Tempra 36 – Best tankless electric water heater

Stiebel Eltron Tempra 36 Plus

The Stiebel Eltron Tempra 36 Plus tankless electric water heater comes from a manufacturer that has been making home heating appliances since the 1920s.


This is one of the largest units in the Stiebel Eltron Tempra Plus series of tankless heaters. There is no venting requirement with this unit since it’s powered by electricity. It features a 99 percent energy efficiency level not to mention a capacity to raise your water temperature as high as 82F at a 4 gallon per minute water flow rate. It also comes with a digital display plus a dial selector that lets you control the output water temperature. With a design that easily fits in a small space, this unit is easy to install as well.


The Stiebel Eltron Tempra 36 Plus performs well when it comes to heating up your water supply. The dial selector offers a lot of flexibility since you can use it to adjust the water flow and the temperature as well. Simply put, it’s a must-have unit especially if your water supply has inconsistent water flow. Another interesting part about its performance is that it is an electric tankless water heater that does not require any venting. Ultimately this makes installation easy.


  • It comes with easy installation
  • Convenient  water flow and temperature controls
  • Great level of energy efficiency
  • Affordable pricing


  • It requires a circuit breaker
  • A bit of throttle at maximum settings

3. Bosch 3000-T Electric Mini-Tank Water Heater

Bosch 3000-T

The Bosch 3000-T Electric Mini-Tank Water Heater will stay quiet while giving you instant access to hot water at any time. It’s a small and compact water heater that fits well in small spaces.


Whether you want to fit it right under your kitchen sink or in a cabinet space in the bathroom, the design of the Bosch Tronic 3000T will easily fit in any small space. The unit can be mounted on the wall since there are brackets included in the package for vertical mounting. However, if you need to mount it horizontally you might need to buy brackets separately. It comes with a sleek design that blends with existing décor in the kitchen or in the bathroom in case you want it out in the open.  It has a water supply capacity of 7 gallons when installed vertically and 5.1 gallons when installed horizontally. The unit draws about 120 volts of electricity to heat up water to a maximum of 145F.

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Once the Bosch Tronic 3000T gets your water heated up, it performs well to maintain the temperature even for a whole day. This unit comes with a thick foam insulation built inside to ensure maximum energy efficiency. In fact, most users noted that it only cost them about $30 while using it over the course of a year; that is a huge saving on your utility bills. Thanks to the Bosch Tronic 3000T’s overall design, you can either use it as the sole water heating source or as a supplement to an existing heater. No matter how you configure it, the unit is set to produce minimal standby loss meaning you won’t experience intermittent cold water flow while taking showers. Installation is also quite the cinch; however, since some plumbing and hard wiring modifications are required, you might need to get some adapters for the connections.


  • Conveniently reduces water-heat-up lag time
  • Compact design that saves space
  • Easy to install
  • Versatile functionality
  • Features built-in insulation for energy efficiency


  • Water pressure performance could be better
  • Brackets for horizontal installation are not included

4. Stiebel Eltron 240 plus – best Electric tankless water heater

Stiebel Eltron 240 Plus

The Stiebel Eltron 240 plus is another water heater from Stiebel featuring a sleek design that will fit anywhere.


This unit comes in a compact build quality that does not require venting.  It also has a quiet operation making it a decent choice for small residential settings.  The Stiebel Eltron 240 plus brings about an intelligent self-modulation technology that allows for 99 percent energy efficiency. With this unit, you can control the flow of your water maintaining a constant stream of hot water during your showers. The digital display makes it easy to monitor your setting. To top it all off, it comes with a 7-year warranty with 3 years on its parts. Now that’s what a generous warranty is all about.


Like most tankless water heater, this unit does not have any standby losses that are common with a tank water heater. The unit is capable of reducing your electricity bills by as much as 20 percent compared to conventional tank water heaters. Although this is not much compared to other units in the list, you can set it to auto-modulation mode to further increase its energy saving capacity. In terms of control, the Stiebel Eltron 240 plus gives you multiple options to choose from with a dial for controlling the water flow as well as the temperature. Plus, the display makes monitoring your settings straightforward. It is also easy to install thanks to its small and compact design that does not require venting.


  • Ideal for heavy-duty usage
  • Easy mounting and installation
  • Decent water flow control
  • Quiet operation
  • Reliably keeps water temperature constant
  • Comes with a generous warranty period


  • It requires circuit breakers that are bought separately
  • Slight water pressure drop at maximum settings

5. Takagi T-KJr2-IN-LP – Best Natural Gas Tankless Water Heater

Takagi T-KJr2-IN-LP

The Takagi T-KJr2-IN-LP Indoor is a budget option you do not want to miss especially if you are on the lookout for a compact unit with anti-freeze protection.


Since it is a small sized tankless water heater, you can easily fit it in small spaces. It is powered by natural gas and has a capacity to heat up water at about 19.5k to 140k BTU per hour. Therefore, the unit can deliver between 99F to 167F of heat to your water supply. Its maximum water flow of 6.6 gallons of water per minute can be adjusted depending on the incoming water temperature of your area. In terms of actual energy efficiency, the unit is capable of 82 percent energy efficiency which is great for keeping your bills from skyrocketing.


Although its installation process is easy, some users reported spending as much as four hours. The instructions are detailed and therefore be sure to check them carefully even if you decide to hire a professional. Venting is required for this unit and you can either choose from vertical or horizontal venting. Additionally, the unit comes with surge protection that does a great job at protecting the unit during electrical spikes. The overall design of the unit best fits a cold climate thanks to the freeze protection that is built inside. Although it only works with direct outside venting, it offers easy access to the control settings for convenience. You also get a generous warranty of 10 years on the heat exchanger and a 5 years warranty on the parts.  

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  • Generous warranty
  • Ideal for cold climates
  • Easy maintenance
  • Smart performance
  • Safety features included


  • Installation takes time
  • A bit noisy
  • Requires outside venting

6. Rinnai RUC98iP Ultra – Best Propane Tankless Water Heater

Rinnai RUC98iP

Rinnai’s is a renowned brand that has existed for over 90 years. Most of their products feature high functionality and extra long warranties. That explains why the Rinnai RUC98iP, comes with a 12-year warranty not to mention a capacity to produce up to 199,000 BTUs.


This unit can supply up to 9.8 gallons of heated water per minute. It is propane and natural gas powered tankless water heater that can easily suit the needs of a residential or commercial setting. It comes with a sleek and compact design that will not only save space but also allow for easy installation anywhere. It is an indoor unit with a variety of venting options including a concentric or twin-pipe PVC option. If you live in an area with an extremely cold climate, you will love Rinnai RUC98iP’s anti-freeze capacity that only uses up 144watts of electricity to stay functional over cold winters.


This tankless water heater has a 0.96 energy factor. It will only draw 2 watts during standby mode and most of this power goes to its electric ignition system. When it’s actively working, you can expect it to only consume about 64 watts. The unit has ultra-low NOx emissions and offers multiple venting options. Thanks to its 9.8 gallons of water per minute, this unit can fill a whole tub with hot water in no time. Most users reported that installation was easy. It also runs quietly making it ideal for both residential and commercial uses.


  • Reputable brand
  • Space saving design
  • Variety of venting options
  • Decent hot water flow rate
  • High energy efficiency
  • Quiet operation


  • Only designed for indoor use
  • It’s pricey but worth it

7. Rheem RTGH-95DVLN 9.5 GPM – Best Indoor Tankless Water Heater

Rheem RTGH-95DVLN 9.5

The Rheem RTGH-95DVLN is a smart tankless heater that comes with built-in intelligent controls to increase energy efficiency by up to 94 percent.


It comes with a stainless steel build that can withstand the elements. You get a remote control that allows you to control the water flow or even further increase the unit’s energy efficiency. The unit also comes with anti-freeze protection that offers protection from temperatures as low as -30F. This means you can use it in extremely cold climates. Since it’s a gas powered tankless water heater, venting is required; however, it comes with a variety of venting options that suit both indoor and outdoor use.


The EZ-Link Wire technology that comes with this unit is a great feature for connecting two independent tankless units and have them working as one. That way, you can get even more powerful performance, especially in a commercial setting. The 0.96 energy factor that the Rheem RTGH-95DVLN comes with is also quite impressive. This unit will outperform most conventional water tank heaters even in high altitude regions. It comes with a freeze protection mechanism that makes it a perfect fit for areas with extremely low temperatures.  Thanks to the high 9.5GPM flow rate, this unit can easily be used with three full-flow showers at once.


  • Offers both indoor and outdoor venting options
  • Features a freeze protection mechanism
  • Easy to use
  • Designed for heavy-duty usage
  • Reliable heating performance


  • Warranty policy could be better
  • Installation might require a professional

8. EcoSmart ECO 27 – Best RV Tankless Water Heater

EcoSmart ECO 27

EcoSmart prides itself on its eco-friendly products. Their EcoSmart ECO 27 Electric Tankless Water Heater features a self-modulating technology that is capable of saving up to 50 percent of water heating expenses.


This unit is built with copper and stainless steel components for durability. The unit can heat up 3GPM in areas like North America that receive groundwater temperatures as low as 37F. It also has a digital control panel that makes it easy to control the water flow as well as the water temperature. While drawing about 112.5amps of electric power, this unit will heat up your water continuously with enough flow to supply hot to water to all the faucets and taps. Plus, the overall sleek chromatic finish requires low-maintenance and blends quite well with another contemporary décor in the house.

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At its price range, the overall performance of the EcoSmart ECO 27 presents a decent bargain. Its modulating technology enables the unit to adjust energy consumption based on how much hot water is needed. This enables up to 50 percent savings on water heating costs. The unit is made with easily replaceable components making it easy to maintain. Most users found it easy to install.

It comes with a compact build that fits in tight spaces which is great for small families. Its digital temperature control can be set anywhere between 80F-140F. Add that to the fact that it can handle water heat up to 6 gallons per minute and you have a heater that can be used with multiple sinks running simultaneously. All in all, the EcoSmart ECO 27 is a mid-range unit that works well for small families living in an area with a moderate climate.


  • Inexpensive
  • Reliable energy efficiency
  • Compact size that fits anywhere
  • It has a high flow rate in warmer climates


  • The water flow rate in cold climates could be better
  • It does not have anti-freeze protection

Buyer’s guide: Factors to consider while buying a Tankless water heater

1. Brand

When you are looking for a high-quality tankless water heater, it is always a good idea to know the best brands. With a reputable brand, you can guarantee quality and reliability in terms of performance. Here are some of the top brands to keep an eye on while in your search.

  • Rinnai – This brand has been around for a century and boasts of decades of creating groundbreaking innovations. It’s a Japan-based brand that constantly improves on its water heating appliances.
  • EcoSmart – EcoSmart puts out a bold claim of producing tankless water heaters that are twice as fast as conventional tank units. Well, looking at units such as the EcoSmart ECO 27, it is easy to see how this claim is true. On top of fast and reliable performance, EcoSmart also prides in producing eco-friendly products.
  • Stiebel Eltron – This brand is from a German manufacturer with close to a century’s worth of skin in the game. Stiebel Eltron is a popular brand among tankless water heaters for a reason. Their products are ideal for high altitude areas plus they boast of safety solutions that meet industry standards.

2. Size

Getting the right sized tankless heater is important since differently sized units feature different hot water flow rates. You will find that most gas-powered units are often larger with a higher flow rate than electric systems. Therefore, before picking a unit, be sure you understand the flow rate you need according to your area.

3. Type of fuel

Since the whole idea of a tankless water heater is to have an uninterrupted supply of hot water, tankless water heaters require a constant supply of fuel/energy to heat up the water. There are three main types of fuel sources; electricity, propane, and natural gas. Propane and natural gas heaters are typically more powerful and faster at heating water than electric heaters.

4. Energy Efficiency

A tankless water heater does not need to continuously heat water while on standby mode. Since the water is only heated once you turn on the shower, most units will be efficiency form the start. However, some manufacturers incorporate additional technology to their products to increase energy efficiency.

5. Venting

Venting options that come with your tankless heater is also an important consideration. Electric heaters don’t require venting, gas-powered heaters (on the other hand) must vent in order to remain functional in the long run. In fact, only indoor units require the most venting. However, if you go with an outdoor unit, be sure to check that it can handle the elements.


With our list of the options, there is no doubt you will be able to find a unit that suits your needs. Whether you live in a cold or warm climate, getting a tankless water heater can afford you the convenience of a fast heated shower. Also, tankless water heaters are not cheap so be sure to pick a unit that comes with a generous warranty as well.

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