Best Tankless Water Heater Reviews 2018

A tankless water heater provides a never-ending supply of hot water because it instantly heats water that passes through the unit.

The idea of having an unlimited supply of hot water is very tempting for homeowners. Who hasn’t wanted to have a nice, long hot shower only to discover that there was no longer any hot water?

If you’ve got a large household and you’re using a 40-gallon tank-based system, that hot water for a shower might disappear in as little as 15 minutes. Even if you take a 5-minute shower, that means only 3 people in your home are getting a hot shower. Then you’ve got to wait for the system to recover to take care of other hot water needs, like laundry and dishes.

If your current system could use an upgrade or your current tank-based model isn’t keeping up, then the best tankless water heater models could be right for you.

Let’s find out more.

Best Seller

Best Value

Stiebel Eltron Tempra PlusEcoSmart ECO 27

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Our Rating: 4.6/5.0Our Rating: 4.0/5.0
Market Popularity: HighMarket Popularity: High



Rinnai RL75iNRheem RTGH-95DVLN

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Our Rating: 4.2/5.0Our Rating: 4.1/5.0
Market Popularity: MediumMarket Popularity: Medium

Tankless Water Heater Reviews

  • The Stiebel-EltronTemura 24 Plus is best used for households that are 3-4 people in size, live in cold-to-moderate climates, and do not require simultaneous hot water use.
  • The EcoSmart is the best value option because of its overall versatility. Even in cold, northerly climates, this tankless system offers 2.7 GPM of hot water support.
  • The Rinnai RL75iN is an excellent medium-demand option for families that need consistent hot water without big simultaneous demands.
  • The Rheem RTGH-95DVLN is perfect for high-demand households that have a natural gas connection. It is 94% energy efficient and supplies up to 9.5 GPM.

Review of the Best Selling Tankless Water Heater

Tempura offers consumers a 5 GPM solution that is incredibly easy to install.

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The Tempura 24 Plus is a fantastic tankless water heater option for almost everyone in North America. At its maximum performance, it can create a temperature change of up to 92 degrees Fahrenheit. That means even homes where the average groundwater temperature is 42F can still receive a healthy GPM and hot water experience.

For the coldest regions, the maximum GPM households will receive is around 2.6 GPM. That is based on the desired water temperature of 115F and an average groundwater temperature of 42F.

In warmer regions, where groundwater temperatures average 72F, the Tempura 24 by Stiebel-Eltron operates at 5 GPM. It offers a water output range that can reach 140F, with a minimum 86F setting.

This model does not require venting.

This water heater can be installed almost anywhere. The design works well for virtually any installation point, thanks to its compact, wider frame when compared to similar systems. Users have access to digital temperature controls for a custom experience every time.

Several features are included with this tankless system to further customize the experience for homeowners in all geographic regions.

  • Energy use is reduced with this system, thanks to auto-modulation
  • Advanced flow controls help the system be able to maintain a consistent temperature
  • Solid copper heating chambers create consistency within the system

With the advanced flow control feature, the system will monitor simultaneous water use throughout the home.

If GPM levels exceed demand, then the system will reduce flow across the board in slight amounts. This feature prevents water temperatures from running cold, unlike other systems from competitive brands.

This system requires a 2 x 50-Amp DP breaker to properly operate

The minimum required wire size and number of runs for this model is 2 x 6/2 AWG. The minimum recommended household electric service to operate this unit is 150-amps. For older homes or homes in communities with outdated electrical infrastructures, there may not be enough amperage to fully support the unit.

The warranty with this product is 3 years for parts and 7 years against leakage.

We got the opportunity to view an installed unit and were quite impressed with the performance it provided. We tested the unit by drawing a bath while running the dishwasher simultaneously.

The total output for the two exceeded the capacity of the unit by over 1 GPM. As promised, the water heater adjusted to the higher demand without compromising the temperature of the water.

It did extend the amount of time that was required to draw a full bath. There were no functionality or pressure issues within the dishwasher. The dishes were cleaned, as expected.

If you’re looking for a model that is easy to install and offers a proven value, then give the Tempura 24 a closer look. There’s a good chance that it will be able to meet the needs you have in your home.

Review of the Best Value Model

The EcoSmart ECO 27 is affordable for every home, in every climate.

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One of the knocks that tankless water heaters receive is their lack of flexibility in cold-

One of the knocks that tankless water heaters receive is their lack of flexibility in cold-weather climates. Because the groundwater temperatures are colder, it takes the unit longer to produce hot water.

For entry-level units, often priced at $400 or more, homeowners would receive less than 2 GPM of hot water support.

The ECO 27 is a different option altogether. It is priced better than some entry-level models, producing better than some premium tankless systems that are on the market today. In warmer climates, homeowners can receive up to 6.6 GPM of hot water support.

In geographic locations where groundwater temperatures average 40F throughout the year, this EcoSmart system provides users with up to 2.7 GPM of hot water. It is configured to work with homes that have average groundwater temperatures as low as 37F.

This model also offers self-modulating technology.

EcoSmart has also incorporated modulation into the ECO 27. If water use levels exceed the maximum capacity of the unit, then water pressure levels are adjusted to maintain output temperatures. It is the largest electric tankless system on the market today that offers this feature at the time of this review.

At the same time, EcoSmart includes a lifetime warranty on the electronics, exchanger, and element with this tankless system. The warranty doesn’t include labor costs, however, so that may need to be taken into account by some users.

For further convenience, a remote control is available, though sold separately, which allows homeowners to control the flow temperature from anywhere in the home.

Power consumption requirements may exclude some homeowners.

Although this water heater offers the best value on the market today, it does require three 40-amp double-pole breakers to operate. The overall power consumption from this unit is relatively low, especially when compared to tank-based systems. It has higher start-up demands, which is why the triple setup is required.

We did notice a correlation between improper installations and a tendency for the unit to turn off unexpectedly. The water heater will operate at a reduced capacity if you don’t connect the three 40-amp double pole breakers. It will also increase the risks of the control card, deciding to turn off.

It won’t trip the breakers if this occurs. It will simply stop working. You may also find that you must cycle your breakers from time to time with an incomplete installation to keep it operating.

For the price, you can’t beat the features and output that the ECO 27 is able to provide. No matter where you happen to live or what your budget might be, you’ll want to take a look at the many strengths this product offers.

Review for the Best Medium-Demand Model

Rinnai helps families avoid schedule conflicts with consistent hot water access.

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The average home has 3-4 people living in 2-3 bedrooms. Maybe there’s a couple of bathrooms in there. If you’ve got a light-demand tankless heater, that’s too much for it to handle.

You’d save money by going with a lightweight GPM rating. You would also force yourself into a specific schedule to allow each person the hot water access they may need.

At the same time, you don’t need a high-demand tankless system when you meet the definition of “average.”

The Rinnai RL75iN fills the gap nicely. Providing up to 7.5 GPM of hot water support, this gas-powered system is compact, mounts in almost any room, and can be directly vented with a roof or single-wall penetration.

The 7.5 GPM rating is based on geographic location and a 120F setting.

Under certain conditions, some households may receive over 9 GPM of hot water support.

We did find it necessary to pay very close attention to the installation specifications with this particular tankless system. It requires a 3/4-inch gas pipe.

You will need to check with your local utility and jurisdiction for building codes. Some homeowners may find themselves excluded from this installation because of this requirement.

Once installed to specs, this Rinnai unit performs as expected. There can be some delays in hot water at the furthest faucets in the home.

For the most part, however, the user experience with this unit is what you’d receive from any other water heater that doesn’t use a recirculation pump as part of its standard insulation.

Check the load on your gas supply lines before ordering as well if you are replacing a gas tank-style water heater.

Tank-style water heaters often operate at 40,000 BTUs per hour. This unit requires 180,000 BTUs per hour. If you don’t have the proper gas supply available, then the unit will not perform as it should.

There are some maintenance needs with this unit, though not outside of the ordinary. Flushing the system is pretty simple and comparable to any other system.

The biggest risk of a breakdown is within the modulation feature, which controls the gas and water flow to the tankless system.

The operation of the unit is very quiet. The water temperature it provides is very consistent.

There is an issue with the burners in this Rinnai unit where they are very sensitive to debris. If the unit senses anything with the burners, then it will flash an error code at you that remains until you clean the burners. Under regular operating conditions, expect to clean the burners 3-4 times per year.

For medium-use homes that want consistent hot water access, we feel that there isn’t a better option on the market today than the Rinnai RL75iN. It may offer some owners a few challenges, though we feel the positives here far outweigh any negatives that might be experienced.

Review of the Best High-Demand System

Rheem offers homeowners up to 9.5 GPM of hot water for large families and households.

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If you have high-capacity hot water needs in your home, then a gas tankless water heater is one of the few options available that can meet your needs. Under certain geographic conditions, this unit can provide up to 9.5 GPM of hot water. That is one of the best rates available in the industry today for residential installations.

That isn’t the only benefit you’ll find with this Rheem unit. It has several performance features that help to enhance the user experience – from our perspective, anyway.

  • It offers a water-saving setting that further reduces water waste in the home. When activated, up to 1,100 gallons of water can be saved each year with this feature.
  • Low-flow activation is available with this tankless system, as well. With hot water available at .40 GPM, low-demand circumstances still receive the right water temperature.
  • This system works with a recirculation pump, making it possible for hot water to be instantly available at the faucet. When installed properly, some homes may save more than 12,000 gallons of water per year.
  • There is a hot-start feature that minimizes cold water bursts from the unit as well.

Rheem offers a 5-year warranty program for this system, which includes commercial installations, on parts. Labor is included for the first 12 months of the warranty.

Residential installations have a 12-year warranty on the heat exchanger, while commercial installations have a 5-year warranty on the exchanger.

Follow all installation instructions with this Rheem unit to the letter.

If the installation is not followed properly, including the installation of the vent, then the warranty could be voided.

Once installed, there are quite a few nice additions to this water heater that makes life better. It offers a built-in condensate neutralizer, which reduces the issues with dampness that some water heaters in this category can cause.

It offers a high-altitude capability as well. Elevations of up to 8,400 feet above sea level are supported by this tankless system.

Homeowners can vent up to 150 feet when using 3-inch PVC or 60 feet using 2-inch PVC.

One of the nicest options, however, is the self-diagnostic system. It will notify you after 500 hours of use to call for an optional service check to ensure it is operating properly. A digital remote control and 10-feet of thermostat wire are included as well.

We found this gas tankless water heater to be fully capable of meeting the needs of virtually any household.

If you have a large home, bigger than 3,500 square feet, or a large family that uses a lot of hot water simultaneously, then this is the water heater you’re going to want to purchase today.

Buyer’s Guide for Tankless Water Heaters

Although tankless water heaters are just starting to become popular in the United States, this isn’t a new technology. The first electric tankless water heater was invented in 1929 by Stiebel-Eltron.

The problem with tankless water heaters has always been related to the efficiency of the unit. It takes time to turn cold water into hot water. Until the 1990s, when water use wasn’t a concern for most communities, tankless systems could not keep up with the amount of water being used.

Older faucets used to operate at 5-7 gallons per minute (GPM). Showers operated at the same level. Even today, industrial-strength tankless systems typically support 10 gallons of hot water per minute or less.

Thanks to technology improvements in water pressure and water flow, most faucets operate at 2 GPM or less (source). Showerheads operate at 2 GPM or less as well (source). That means a tankless system with 6 GPM of hot water support can theoretically support 3 simultaneous showers with an endless supply of hot water.

In the past decade, innovations within the tankless industry have helped to push down costs per unit as well. The cost of a new tankless system, either gas or electric, is comparable to the cost of a brand-new tank-based water heating system.

Yet a tankless water heater may not be the right choice for some homes. Here are some of the important key points to consider.

Gas vs. Electric

Electric water heaters are the easiest to install. They can save water, save energy, and can be placed virtually anywhere.

Gas water heaters are much more difficult (and costly) to install. In return for the investment, however, you receive higher GPM ratings and better efficiencies in your hot water system.

Tank vs. Tankless

The conventional tank-based system stores water that is constantly heated. Tankless systems will take cold water, heat it with an element or gas burner, providing on-demand hot water.

Hot water tanks can be stored in garages, closets, or a basement. Top models today can store up to 80 gallons of hot water and may have a first-hour rating (FHR) of 100 gallons or more.

Tankless systems can be wall-mounted. Although they require venting, they also free up a lot of floor space. They’ll also reduce energy consumption, for households that use 41 gallons of hot water, or fewer, by at least 20% in almost every circumstance.

GPM Flow Rates

In the average home, a dishwasher, a shower, and a washing machine would use 7.5 gallons per minute of hot water if operating simultaneously.

That means you’d need to purchase a premium model to meet that demand. After all, entry-level models provide 2 GPM of support.

You can reduce your simultaneous GPM needs by staggering your hot water usage. If you’re on a budget, purchase a unit that can meet the peak demand needs of your largest appliance.

A dishwasher requires 2.5 GPM of hot water. Washing machines can use 3 GPM. Older kitchen faucets may require an upgrade since they can use 7 GPM.

In the average home, a dishwasher, a shower, and a washing machine would use 7.5 gallons per minute of hot water if operating simultaneously.

That means you’d need to purchase a premium model to meet that demand. After all, entry-level models provide 2 GPM of support.

You can reduce your simultaneous GPM needs by staggering your hot water usage. If you’re on a budget, purchase a unit that can meet the peak demand needs of your largest appliance.

A dishwasher requires 2.5 GPM of hot water. Washing machines can use 3 GPM. Older kitchen faucets may require an upgrade since they can use 7 GPM.

Add another 0.5 GPM for each sink in simultaneous use. Then add all your peak demand needs together to reach a target GPM for your tankless system.

Climate Impact

Tankless systems struggle to operate when ground temperature averages are quite cold. You must think about what the actual temperature change will be to determine the strength of the system you require.

Some geographic regions in the United States have an average ground temperature that is as low as 35F. That is a 12-month average. If you want 120F hot water, you would be required to purchase a tankless system with a maximum heating capacity of 85 degrees.

Most systems do not have the capability of making that happen.

Most tankless systems work best under conditions where a 60-degree or less water temperature change is required.

Installation Costs

Installing a brand-new tankless system can be an expensive proposition for some households. Gas-powered systems can be especially problematic because of their venting requirements.

You cannot stack vent a gas tankless unit with a furnace or other appliance.

According to Home Advisor, the average cost to install a new tankless system in the U.S. is $1,783. Costs may be as high as $2,740. That is because there are venting requirements that must be fulfilled for some systems. Gas lines may need to be added. Water lines may need to be shifted or changed.

As a general rule of thumb, it is a good idea to consider a tankless system if you have a new construction project, or you are replacing a current system if gas is your fuel source.

If you’re replacing a gas water heater tank, it is cheaper for most homes to purchase one of the best gas water heaters instead.

Location of the Installation

Some people may also be wondering where they should install a tankless water heater in their home. While it might not seem like a major consideration to keep in mind, it definitely will prove to be. The location you choose for installation will ultimately also determine how it functions.

You want to be sure that it is put where you will have easy access to it. This is in the case of any adjustments or maintenance that is needed or any repairs that the water heater requires.

If you already had a tankless water heater in the home and you are installing its replacement, then that same location is probably going to be just as ideal as it was for the last model. The plumbing is also already done, so that’s always a bonus too.

You should also be sure to read the instruction and owner’s manual for your new tankless water heater to see if there are any special requirements or recommendations when it comes to installing the unit.

Once you find the space, pay close attention to the electrical outlets, shared plumbing lines, and other areas close by that could ultimately cause complications or disaster like fire or flooding.

Tips for Tankless Water Heaters

What better advice than getting it from people who already own and use tankless water heaters? They recommend understanding your power needs that your new system will require. Sometimes you may require additional room on the electrical panel and that is definitely something you will want to know ahead of the installation process.

Tankless water heater owners also want to remind people that it may be a few years before they can begin seeing the savings and energy efficiency that this kind of water heater affords. So, they suggest not looking at the tankless water heater as an investment but more of a convenience.

The Pros and Cons

Finally, we have some pros and cons for you to consider before you make your purchase.


You will have hot water on demand. This is especially good for families that have four or more people in the household.

Endless hot water. Hot water on demand is nice as we have already touched on, but there is also something to be said about an endless supply of hot water that is immediately available. You won’t have to worry about running out of hot water during another shower again.

They last a long time. Regular, standard tank hot water heaters were designed to last upwards of 18 years with proper care and maintenance. Tankless hot water heaters, on the other hand, are said to last twice that long. All you have to do is make sure to keep up with all the maintenance that is required.

Ideal for small spaces. If you don’t have much room to work with in your home, then this kind of water heater can save you some space.

Environmentally conscious. You will find that most tankless water heater models have a 95% plus energy rating and don’t emit any greenhouse gases.

Add value to the home. Finally, adding this premium feature to your home lends to its overall value. It is a great selling point down the road if you decide it is time to move and you want to strive for top dollar for your home.


It is a luxury. Energy star certified appliances are good, but you won’t see the savings on your energy bills for years which makes a tankless water heater seem more like a convenience and luxury item rather than an energy saving investment.

Higher costs. With this kind of system, you will also find that the costs may be much higher than standard water heaters. If you have hard water, you will need to have a water softener installed to avoid wearing out and damaging your tankless water heater. Some homes may also need additional plumbing for it as well.

Varying levels of hot water. Depending on how many people are using the hot water, there may be small variances and fluctuations in the hot water supply. If more than one person is taking a hot shower and laundry or the dishwasher are also being run at the same time, then that may also have a significant impact on the consistency of the hot water.

Warranty Concerns

Most tankless systems void the warranty for their water heater if the unit is self-installed. Some void the warranty if the unit is not purchased from an authorized dealer. A warranty might be voided if a utility technician does not install the electrical or gas lines.

Be sure to read through all warranty stipulations before finalizing any purchase to ensure you receive the full protection levels you deserve.

What Is the Best Tankless Water Heater for Your Home?

Tankless water heaters provide a lot of convenience for the modern lifestyle. They supply hot water on-demand, eliminating the need to constantly store and re-heat water.

That means you eliminate almost all standby energy costs. At the same time, you can receive unlimited hot water as long as your demand levels do not exceed the peak capacities of the unit you’ve installed.

There are several considerations that must be evaluated by each household. Every tankless system offers specific advantages and disadvantages for homeowners, no matter what their geographic location may be.

Without a careful evaluation of each feature, the costs of purchasing and installing a tankless system could seem like a waste of money.

Keep your family size in mind when shopping. Think about your average groundwater temperature – not what the temperature might be in Summer. Evaluate your simultaneous hot water consumption needs.

Once you have that information, then you’ll be ready for the best tankless water heater reviews. Make the investment, which makes sense for the needs of your family.