Best Tankless Water Heater Reviews

tankless heaters

 Switching from a tank water heater to a high-efficiency tankless water heater is one of the smartest decisions you can make for your home. Not only will you immediately see energy savings of up to 60 percent, but you’ll also have continuous on-demand hot water.

Furthermore, a top-rated tankless water heater lasts at least 20 years, compared to a maximum of just 15 years for an electric tank heater and 12 years for a gas tank heater. Finally, even the largest tankless units takes up far less space and requires less maintenance than a tank unit with a storage tank.

But what is the best tankless water heater for you?

Most people are unsure about what to look for when selecting the perfect tankless water heater. We can help you figure it out with our comprehensive review and buying guide. As well as providing you with the information you need to assess your home’s specific water heating needs, we will compare tankless water heaters from all the top brands. 

Top 10 Tankless Hot Water Heater Picks 

  • 9.8 Max GPM
  • 96% Efficiency Rating
  • Gas Powered
  • 9.8 Max GPM
  • 96% Efficiency Rating
  • Gas Powered
  • 8.4 Max GPM
  • 82% Efficiency Rating
  • Gas Powered
  • 9.5 Max GPM
  • 94% Efficiency Rating
  • Gas Powered
  • 6.6 Max GPM
  • 83% Efficiency Rating
  • Gas Powered
  • 4.0 Max GPM
  • 99% Efficiency Rating
  • Electric Powered
  • 4.3 Max GPM
  • 99% Efficiency Rating
  • Electric Powered
  • 6.6 Max GPM
  • 99% Efficiency Rating
  • Electric Powered
  • 1.7 Max GPM
  • 98% Efficiency Rating
  • Electric Powered
  • 3.0 Max GPM
  • 99% Efficiency Rating
  • Electric Powered

Top Tankless Water Heater Models Reviewed

Let’s take an in-depth look at each of the instant hot water heaters listed in the comparison chart.

1. Rinnai RUR98iN (Top Overall)

Together with the other Rinnai model, the RUR98iN is the highest gallons per minute tankless water heater. It is also powerful in temperature rise — again, joint first — offering a rise of 60 degrees Fahrenheit. This means it is able to meet the whole-house needs of almost any home even in cold climates.

Arguably one of the best tankless water heaters of all, it also maintains an energy efficiency of 96 percent. In part, this is due to the dual heat exchangers, which allows the heater to use water condensation as an extra energy source.


  • Great efficiency rating- .96 energy factor
  • High-temperature rise- 60 degrees F
  • High flow rate GPM- 9.8
  • Condensing unit with dual heat exchanger


  • Expensive

2. Rinnai RUC98iN (Indoor)

Wherever you live, the Rinnai RUC98iN is an ideal tankless water heater. Cold climate or hot climate, it has you covered. With a temperature rise of 60 degrees Fahrenheit, you’ll receive sufficiently heated water even if your city’s water is quite cold.

Like the RUR98iN, this indoor model is designed for natural gas. However, there is also a propane and an outdoor stainless steel tankless version available. Unlike some gas hot water on demand units, this smart tankless water heater is very quiet, which means having it indoors is no problem. Plus, although it provides you with a very large amount of water, it takes up a minimal amount of space, especially when compared to a similar-capacity tank model.

Although it is one of the more expensive models, the RUC98iN deserves to be named as a top 5 tankless water heater in the gas range for its number of advanced features. For instance, it is WiFi enabled for monitoring and changing settings. There is also the option of recirculation. This eliminates the need to flush cold water out the pipes before any hot water can come through the faucet.


  • Great for any climate including cold climates
  • Powerful, high flow rate of 9.8 GPM
  • Suitable for large homes
  • Compact design


  • Expensive

3. Rheem RTG-84XLN (Outdoor)

The Rheem RTG-84XLN is one of the best instant hot water heaters if you want an outdoor model that is affordable and that will provide you with high flow rates of up to 8.4 gallons per minute. Reviews of the best gas water heaters rank this model at the top for providing everything you could need in an outdoor model. For instance, it has a remote control, which allows you to adjust settings without needing to access the heater itself.

This water heater also offers a decent energy efficiency of 82 percent and it is low emission. The lack of need for ventilation is appealing to many homeowners who want the cost savings of  gas water heaters without the hassle and expense of a complicated installation.


  • Ideal for average-size homes
  • Lower cost than other gas models
  • Remote control
  • Low emissions
  • HIgh flow rate- 8.4 GPM


  • Mid-efficiency
  • Only suitable for warm climates

4. Rheem RTGH-95XLN (Best Outdoor)

This high-capacity tankless water heater offers 9.5 gallons per minute, making it an excellent option for large homes. At 94 percent, it has better efficiency than the other Rheem models, although this along with the greater power does increase its price tag. The good thing is that it is an outdoor heater, which means there is no need for ventilation.

In fact, when you compare tankless water heaters for outdoor use, this insta heat water heater is right near the top. It is rare to find an outdoor unit with such high energy factor ratings. Plus, it is manufactured by Rheem, a brand known for top quality.

Finally, with a temperature rise of 35 degrees Fahrenheit and protection from the elements, it is suitable for warm and even rainy climates.


  • Perfect for average-size to large homes
  • High efficiency for gas
  • No need for ventilation
  • High flow rate, 9.5 gallons per minute


  • Expensive
  • Low-temperature rise

5. Takagi T-KJr2 IN-NG (Indoor)

Another Japanese tankless water heater, the Takagi T-KJr2 is much less expensive than most gas models but offers close to the same quality. It is ideal if you are looking for a slightly lower flow rates of around 6.6 GPM from your tankless water heater. Japan brand Takagi is well-known in the water heater industry for its innovation, something which is apparent with this heater. As an example, the heater is designed with maintenance in mind — you can take it apart and access all the parts with ease.


  • Low cost
  • Easy maintenance


  • Lower flow rate/GPM than other gas units
  • For hot climates only
  • Mid-efficiency

6. Stiebel Eltron Tempra Plus 24 (Best Electric)

This German tankless water heater is the flagship product from Stiebel Eltron. It has a GPM of 4.0, which is decent for an electric instantaneous water heater. One of these heaters is suitable for a small home, whereas two can provide enough power for a large home. The heater also has a reasonably high-temperature rise of 43 degrees Fahrenheit along with 99 percent energy efficiency.

If you compare all of the best electric tankless water heaters, you’ll see that the Stiebel Eltron Tempra Plus 24 consistently comes out on top. The European tankless water heater has a slightly higher price tag than some of the other models. This is likely due to its digital controls and convenient design, which allows it to be a wall-mounted water heater or for it to be hidden out of the way under the sink, behind a furnace, or within a utility closet.

These features combined make the Tempra Plus 24 one of the best tankless water heaters in the electric range.


  • High efficiency
  • Digital controls
  • Great design
  • Average flow rate of 4 GPM


  • Point of use or small home only
  • Expensive for an electric unit

7. Eemax EEM24027 (Electric)

The Eemax EEM24027 can supply enough water to a small home while wasting almost zero energy. Provided that your city water temperature is not too low, you can even run several appliances at once. The heater has self-modulating technology to adjust energy usage to demand at any given time.

Although it is reasonably powerful for an electric tankless water heater, it is small in size. This allows you to install it wherever you want, including in a closet for a bathroom or under the sink in the kitchen as a point-of-use heater.


  • Excellent efficiency rating
  • Self-modulating technology
  • Compact


  • Point of use or small home only

 8. EcoSmart ECO 27 (Electric)

A high GPM of 6.6, a decent temperature rise of 43 degrees Fahrenheit, and an excellent efficiency of 99.8 percent make the EcoSmart ECO 27 a top choice. Combined with a price tag of just $450, this is another strong contender to be included as one of the best-rated tankless water heaters in the electric range.

One of the larger insta-hot water heaters in the EcoSmart ECO series, the ECO 27 can function as either a point-of-use heater in an average-size or large home or as a whole-house unit in a small household. Manufactured by a reputable (although lesser-known) brand, it is one of the most reliable models you’ll find.

You’ll also receive a lifetime warranty for the heating elements, provided you receive professional installation.


  • High GPM for an electric model
  • Excellent efficiency rating
  • Lifetime warranty


  • Warranty requires professional installation

9. Sio Green IR288 (Best Small Point of Use)

The smallest tankless heater on the list, the Sio Green IR288 has a GPM of just 1.7. It is also the lowest cost, but it still has a high energy rating of 98 percent and a perfectly fine temperature rise of 40 degrees Fahrenheit.

These characteristics make it a great option for an RV or point of use need. In fact, the simple installation means that it could work as a dual-purpose water heater: you can remove it from your RV when not on the road and install it under a sink or next to an appliance.

The Sio Green IR288 is free from metallic elements, which means that there is no risk of corrosion. You can simplify maintenance even further by purchasing a water softener — water heater units that are processing hard water will always benefit from a softener.


  • Inexpensive
  • High efficiency
  • No risk of corrosion
  • Ideal for an RV


  • Low flow rate with GPM of 1.7

10. Rheem RTEX-18 (Electric Point of Use)

Rheem doesn’t just manufacture gas models — it also has the RTEX-18, one of the top electric wall-mounted hot water heaters. With an external thermostat control, you have great control over the temperature. You can also leave the heater to use self-modulation. This will adjust the power to heat water to the extent you need it without wasting energy.

The Rheem RTEX-18 is also the quietest tankless unit around — it makes no noise at all. This means you can install it wherever is most convenient in your home without needing to worry about being disturbed. Features like this are what makes the RTEX-18 a top choice for a point of use model.


  • External thermostat control
  • Self-modulating technology
  • Quiet
  • Excellent efficiency rating


  • Low flow rate 

Other Tankless Water Heater Brands We Reviewed

So far, we have seen the tankless water heater brands Rinnai, Rheem, Takagi, Stiebel Eltron, Eemax, EcoSmart, and Sio Green. However, when drawing up a list of the top 10 models, we also considered several other water heater manufacturers.


Noritz is a supplier of premium water heaters for both residential and commercial usage. All the brand’s water heaters are tankless; they range from mid efficiency to high efficiency. The most powerful can provide enough hot water demand for at least five bathrooms.

The highest-rated tankless water heater from Noritz is the NRC98-DV-NG. It is praised for its high flow rates and condensing system. Plus, it is an indoor water heater, which means there’s no need to worry about finding a secure place to install it outdoors.


Eccotemp manufacturers gas and electric tankless units as well as mini water heaters, all at a reasonable cost. You can purchase the heater alone or with a service kit, with a venting kit, or in a portable bundle. If you’re looking for an off-grid tankless unit, Eccotemp is a good choice. For instance, the brand has water heaters designed specifically for use in cabins. All the heaters stand out for their unique look — for instance, some models are available in black as well as the standard white and gray.


Navien only produces condensing water heaters with dual stainless steel heat exchanges. This allows for the lowest possible energy consumption and greenhouse gas emissions as well as for the longest possible lifespan. All the heaters are energy efficient and energy star  certified and they come with a 15-year warranty for the heat exchangers.

One of Navien’s top models is the NPE240S-NG. This natural gas-powered heater is quiet enough to be anywhere within your house, thanks to intelligent preheating. It is also easy to install and is even field convertible.


Producing only electric water heaters, Atmor is one of the most popular manufacturers in the world. The heaters allow you to choose between four different temperature levels according to the season, any of which will provide you with hot water in just 15 seconds.

Atmor is a top choice for an inline tankless water heater. The heaters in its inline series connect straight to your home’s main hot water line for use with appliances like low-flow showers.


Bosch promises to help you save up to 50 percent on your utility bills by changing from a  water heater with a storage tank to one of the brand’s tankless versions. All the water heaters are gas-powered, energy-efficient, whole-house units. The smallest offers 8.3 GPM along with a 35-degrees fahrenheit temperature rise. The largest is a condensing unit with 12.1 GPM and up to 98 percent efficiency. All the water heaters come with a 15-year warranty on heat exchangers and have a 20-year life expectancy.


Marey produces gas and electric models, with free shipping for products within the mainland U.S. The gas heaters are available as duct exhaust, force exhaust, or portable, whereas the electric heaters are point-of-use, whole-house, or mini models. All are very affordable, especially considering that they offer mid-range efficiency.


Designed for residential or light commercial use, Paloma water heaters are available as indoor and outdoor units. The gas heaters feature carbon monoxide safety protection. This means that if the system detects carbon monoxide, it shuts down and shows an error code. Paloma has one energy star tankless water heater: the PHH-32. This is the only condensing model. It is also Low NOx and has a high GPM of 9.5.


Titan only manufactures tankless water heaters. It currently has eight different products, designed for a range of applications. Many of its most powerful are suitable for all climates, including for the northern-most parts of the country. Its top-range models feature a digital control interface for settings and diagnostics.


Richmond manufacturers a variety of water heater products including traditional storage tank models. Its gas tankless heaters are either mid efficiency or condensing. Both types use a self-diagnostic system for improving troubleshooting. The electric range features both point-of-use and whole-house water heaters. The smallest have a GPM of up to 0.9, whereas the largest has 8.8 GPM, which is plenty for an average-size home and can even suit a large home, provided that it is unlikely you’ll need hot water for many appliances at the same time. These more powerful models also have self-modulating power control to heat just the water you need and nothing more.


Hot water systems from State come with a 15-year warranty. All the heaters are gas and can use either natural gas or propane. They are also all either Low NOx or Ultra-Low NOx. The largest of all have a GPM of more than 10, which is more than enough for any home and sufficient for more commercial uses. Technologically-forward, many of the models feature digital displays and come with remote controls for changing settings without needing to access the heater.

How to Select the Right Size and Type of Tankless Water Heater for Your Home

It can be hard to figure out which model is best for your home just from reading the above comparison chart. What GPM do you require? What about temperature rise? Is gas or electric better for your home? Is installing indoor or outdoor better? All this depends on the size of your home and your needs. 

Below, we will walk you through how a tankless water heater works to help determine what size and type of heater is best for your needs.

1. Determine the Flow Rate You Need

The flow rate of a tankless water heater is represented by its GPM. This is the maximum gallons per minute you can expect to receive. You can work out what flow rate you would need for a whole-house unit by adding up the requirements of each of your appliances in your house.

Appliances with the lowest needs from a tankless water heater are sinks. Both the kitchen and bathroom sink require only about 0.5 GPM. Next, you have the dishwasher: at 1.0 GPM, this has needs twice as high. A washing machine requires a slightly greater flow rate still, at 1.5 GPM. Finally, you have your showers. A standard shower requires a GPM of 2.5, whereas a low-flow shower needs just 1.5 GPM.

Flow Rate (GPM)
Bathroom Faucet
bathroom faucet
0.5 GPM
Kitchen Faucet
kitchen faucet
0.5 GPM
shower head
2.5 GPM
1.0 GPM
Clothes Washer
washing machine
1.5 GPM

You’ll need to consider how many of your appliances you’ll likely want to use at the same time. Add them together to pick the appropriate flow rate for your water heater.

Alternatively, you could consider the average GPM for your size of home. For instance, an apartment or condo with one bathroom will need an automatic instantaneous water heater with about 3.0 GPM, whereas a small house of less than 1,000 square feet will need 4.0 GPM. An average-size home (between 1,000 and 1,600 square feet) with two bathrooms will need a residential tankless water heater with a GPM of around 7.5.

Finally, a large house of more than 1,600 square feet with three or more bathrooms will need a high-flow tankless water heater with a GPM of close to 10 — or maybe even more.

All the above assumes that you have a local water temperature of at least 67 degrees Fahrenheit. If your water temperature is lower than this, you’ll need a slightly higher GPM. In such a case, you should either pick a recommended tankless unit that offers high power or install more than one of the point-of-use heaters named in our guide.

2. Pick the Right Temperature Rise Capability

Your local water supply impacts the temperature rise you require. In the warmest regions of the country, the local water supply can be as high as 77 degrees Fahrenheit. In the north of the U.S., though, it can be as low as just 35 degrees Fahrenheit.

This temperature can also have an impact on how long it takes for your water heater to heat up.

The US groundwater map below will show you your local water supply temperature.

us groundwater temperatures

To figure out the temperature rise you require, you need to consider the ideal temperature for different appliances. A shower is most comfortable at between 102 and 105 degrees Fahrenheit. You may like to have the kitchen sink slightly hotter still — at as much as 110 degrees Fahrenheit.

Example Home 1: One Bathroom, Hot Climates

Based on the above criteria, a no-tank water heater for an apartment with one bathroom and one kitchen sink, a single shower, and a dishwasher but no washing machine would need to offer 4.0 GPM. Of course, if you decide to run fewer appliances at once, you could manage with a lower GPM.

Next, let’s suppose that this home is in a hot location where the incoming water temperature is 75 degrees Fahrenheit. You would only need a temperature rise of 35 degrees Fahrenheit, which allows you to pick from any of the models named in our review.

Example Home 2: Two Bathrooms, Average Climates

For a second example, let’s look at the needs of an average-size home with two bathrooms. Such a house would likely have two bathroom sinks, two showers, one kitchen sink, a dishwasher, and a washing machine. A tankless water heater for a 2-bathroom house, therefore, would need to offer a GPM of 8.5 to provide all the appliances with water at the same time. However, since it is unlikely that water needs would ever be this high, the house would manage fine with 7.5 GPM.

In addition, we need to think about the temperature rise. To provide hot water in an average climate (where the incoming water temperature is around 54 degrees Fahrenheit), the water heater would need a temperature rise of at least 48 degrees Fahrenheit.

Example Home 3: Three Bathrooms, Cold Climates

Finally, let’s consider a large home — for instance, with four bedrooms, three bathrooms, and an in-law suite. Such a home would likely have three showers, three bathroom sinks, two kitchen sinks, two dishwashers, and two washing machines.

To choose the right GPM, the homeowners would need to think about how many appliances they are likely to use at the same time. They would probably need a GPM of at least 9.0. For this reason, they should consider only one of the high-powered gas models that is suitable for suburban whole house use. Alternatively, they could install multiple point-of-use electric heaters.

To manage the cold climate, an instant-on water heater would need the highest possible temperature rise. Supposing that the incoming water is 47 degrees Fahrenheit, the heater would need a 60-degrees Fahrenheit temperature rise. This would be extra important to keep receiving close to the maximum GPM — as the GPM a heater is able to supply is lower when it needs to heat water to a greater extent.

3. Choosing Between Gas and Electric On-Demand Water Heaters

gas vs electric fuel

It is possible that your home only has access to one type of energy source. In this case, it isn’t necessary to consider the power source for your flow-through water heater. For instance, if you have no gas line, it will likely be too complex to install a gas heating system. On the flip side, if you do have the option for either a gas or electric tankless water heater, you’ll need to know the pros and cons of each.

Do You Want Whole House or Point of Use?

Gas will usually provide you with the best whole-house option. The higher GPM of gas tankless boilers means they are better able to provide hot water to multiple appliances at once.

On the other hand, if you’re looking for a point-of-use heater, such as one for your shower water or for a hot tub, electric will be sufficient. Similarly, electric is fine for small homes with low water heating needs.

Compare Tankless Water Heater Costs

Another advantage of gas is that the operating costs tend to be much lower than for electricity (although there is the chance that fuel prices could change in the future). The exception is if you are using solar panels installed on your house.

However, whereas operating costs for gas tend to be lower, upfront expenses are higher. The purchase price and installation costs are almost always more for gas than for electric. The price rises still further if you choose an indoor gas continuous hot water system, as it will require ventilation. This means that, although a gas-powered unit will likely provide you with the better value over time, it will be more expensive in the short term.

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

What Is More Environmentally Friendly?

Electric heaters are more environmentally friendly than gas heaters, even when compared to gas units with the highest ratings. You can make your electric heater more environmentally friendly still by gaining power from a clean energy source. In addition, many homeowners find electric heaters more appealing as they do not directly emit CO2. This lack of emissions as the added advantage that less maintenance is necessary to keep the heater safe.

So, Which Tankless Water Heater Do We Recommend?

Whether your tank water heater is reaching the end of its life and you want to upgrade to a model that will last longer or you just want to stop spending so much on your energy bills and instead see energy savings, you need to make the switch to an insta hot tankless water heater.

As you have seen, the right choice for your home will depend on your unique water heating needs. What you need in terms of GPM and temperature, your budget, and whether you would prefer gas or electric. The above tankless water heater reviews and buying guide will help you make the right decision.

But, if we had to recommend one whole house model that would take care of your home water needs and do it efficiently and powerfully we would suggest purchasing the Rinnai RUR98IN model.

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