The Best Tankless Water Heaters in 2021 (Reviewed & Compared)

Looking for the best tankless water heaters? We tested more than 20 products from 10 reputable brands based on the following:

• Efficiency and energy conservation
• The value they offer for their respective costs (including installation)
• Flow rate
• Build quality
• Warranty
• Professional and user reviews
• Temperature rise

Read on and find the best tankless water heater for your needs.

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Overview

The Rinnai RU199iN was marked as our best tankless water heater, to start, because it’s a compact, indoor unit that uses natural gas. It’s easy to use and install, and you can place it in several spots around the house. This can range from three to six fixtures.

Important Specs

Its BTU range goes from 15,000 to 199,000, meaning it can heat the water at a highly impressive rate. This model is Wi-Fi capable, so you can monitor the temperature remotely. The maximum water flow rate of 11 gallons per minute is more than enough for most households. 

Durability

This is the best tankless water heater on gas power, it’s exceptionally durable, and it comes with excellent warranties. The residential heat exchanger has a 15-year warranty, the residential parts have a five-year warranty, and the residential labor comes with a one-year warranty.

Pros:

• Easy to install and maintain
• Efficient and durable
• Great value for the money
• Very high GPM

Cons:

• Slightly expensive because it’s a gas water heater

Overview

One of the most trusted industry leaders, Stiebel Eltron, came up with its Tempra Plus design to revolutionize tankless water heating. The brand’s best electric tankless hot water heater never runs out of hot water, even when the demand is very high.

Important Specs

The GPM of 4.5 is more than enough to keep the entire household continuously supplied with hot water. This product has such a compact design that it can fit almost anywhere in the house. It’s also utterly silent, which is a nice bonus.

Durability

The installation is a cakewalk, the service life is very long, but the warranty still is more than fair. You get a seven-year warranty for leakage and a three-year warranty on materials and craft. 

Standard Compliance

Finally, as the best tankless electric water heater, the Tempra Plus meets the ISO 9001, WQA, and UL standards, and it’s certified by each. These certificates are a huge plus because they assure customers of the product’s quality and safety. 

The ISO 9001 is an international quality management standard by the International Organization for Standardization. A Water Quality Association certification stands out as the most trusted and reliable. And Underwriter Laboratories has been issuing third-party certifications for more than a century.

Pros:

• Affordable yet durable
• Trusted brand
• Never runs out of hot water, even under heavy demand
• Environmentally friendly

Cons:

• Some users reported temperature fluctuations

Overview

Takagi is one of the best tankless water heater brands in the industry, with more than 60 years of experience. It sells exclusively through contractors and wholesale plumbers. The company offers a wide selection of tankless water heaters, but the T-H3-OS-N is one of the best outdoor models.

It’s a powerful heater, with a serious GPM that makes you forget about ever running out of hot water. What sets this unit apart is the copper-alloy primary heat exchanger, which is up to 25 times better than stainless steel.

Important Specs

This is an ultra-low-emission option, nearly the best gas tankless hot water heater on our list, even though it uses natural gas. 

Its maximum BTUs are up to 199,000. British Thermal Units represent the amount of energy required to elevate the temperature of a pound of water by one Fahrenheit—a high BTU rating equals more power. Tagaki’s model falls into the top end of the standard BTU range that most tankless water heaters offer.

Finally, there’s an Easy Link option that can support four units, but it goes up to a whopping 20 units via the remote control, which is always included. Last not least, there are safety features against surges, freezing, and overheating.

Durability

There’s a 15-year limited heat exchanger warranty and a five-year parts warranty. The secondary heat exchanger is 316L stainless steel, which is resistant to corrosion. 

Pros:

• Great warranty
• Certified and secure
• Terrific value for money

Cons:

• Some users complained about vibration

Overview

The Rheem RTGH-95DVLP-2 is an efficient condensing tankless gas water heater. It doesn’t run out of hot water, and it has a robust flow rate. 

Even better, its water savings setting saves about 1,100 gallons of water annually when activated. It slowly decreases the water flow until the set temperature is reached. 

Design Features

What’s excellent about Rheem’s best tankless hot water heaters is that they have low flow activation, perfect for low demand situations. There’s also a recirculation pump kit that saves up to 12,000 gallons of water a year.

Rheem even thought of temperature fluctuation, thus minimizing any cold water bursts by design. The installation is straightforward, and so is the service.

Important Specs

Finally, there’s a self-diagnostic system, maintenance notice settings for easier servicing, and a digital remote control. All of the best propane tankless water heaters from Rheem also come with EcoNet mobile app integration, available in the accessory kit.

Lastly, this unit can work even in high altitudes, up to 8,400 ft above sea level. The basic option can support up to six units, and the advanced control board supports up to 20 units.

Pros:

• Remote control and smartphone app control
• Provides support for up to 4 bathrooms
• Works even in very high altitudes

Cons:

• Some users complain about cold water bursts

Overview

Tankless water heater reviews highlight the smart controls the EcoSmart ESG-95 offers for increased security and performance. It’s a mid-efficiency tank that can conserve up to 1,100 gallons of water a year thanks to its reduced water flow.

The minimum flow rates are 0.26 GPM and 0.40 GPM for activation. This translates to a constant influx of hot water, even when the demand is low. The recirculation pump kit is there to give instant access to hot water.

Important Specs

There’s a maintenance notification setting that lets you know it’s time for a service check. Even the tankless water heater installation is intuitive, and you can set the unit up almost anywhere you want.

The concentric vent system has a built-in condensate collector. The smart design of this tankless water heater minimizes instances of blasts of cold water.

Combining Units and Safety

If you need to link up two tankless heaters, you can do that with the EZ Link cable. Finally, even though this is a gas unit, it has an ultra-low NOx burner that meets safety requirements. NOx stands for nitrogen oxides, which are reactive, toxic greenhouse gases. 

The best tankless water heaters will often have ultra-low NOx units like this one, which emit only 7–15 parts per million. In other words, ultra-low NOx technology is two times safer, if not even more. Not only that, but it’s also more efficient.

Pros:

• Eco-friendly despite running on gas
• Robust design that always delivers hot water
• Quality build

Cons:

• A bit expensive for a mid-efficiency unit

Overview

The Eemax HA018240 water heater is labeled for residential use—for multiple or single points of use. It provides steady, never-ending, on-demand hot water. It has excellent temperature control with a 60° F leeway.

Durability

The materials used for this unit are very sturdy. The cover material is stainless steel, and so is the color. The element material is copper. The minimum operating pressure is 35 pounds per square inch, and it goes up to 150 PSI.

Important Specs and Standard Compliance

Overall, the design of this best-rated electric tankless water heater is simplistic and functional. It serves its purpose but lacks many of the fancy add-ons you get from top-tier units—which are significantly more expensive than this one.

This Eemax electric heater has an adjustable thermostat. It’s UL listed and certified. It complies with low-lead UL standards and the Uniform Plumbing Code, which governs the inspection and installation of plumbing systems to improve the public’s health, welfare, and safety.

Pros:

• Superb temperature control
• Can fit anywhere
• Sufficient for small to medium households

Cons:

• Warranty details lacking

Overview

In the point of use category, the SioGreen IR 288 is one of the best tankless water heaters on the market. It has a good flow rate at a 30° F temperature rise. Plus, it reduces energy costs by up to 65%, so it’s well worth the buy.

Durability

Put simply, it’s durable, lasting over 10 years. It is corrosion-free and self-maintaining. The setup is intuitive and straightforward. Even though it provides a sustainable flow, it uses low amperage—the voltage is 220 volts, and the wattage is 8.8 kW, while the amperage is 37 Amperes.

Important Specs

This model comes with a thermostatic intelligent temperature controller, fully modulating power control, and an LED temperature display. For all these reasons, it’s one of the best electric tankless water heaters on the market.

You’ll save energy and space with this product. It’s also very safe, with overheat thermal cut-off fuses, anti-scald protection, and residual current leakage detection.

Pros:

• Easy setup, maintenance, and use
• Low energy consumption
• Significant savings for a cheap tankless water heater

Cons:

• The temp monitor is in Celsius

Overview

The Bosch Greentherm 9000 is one of the best tankless water heaters with gas heating. It has an extraordinary design with integrated drain ports and top connections for water. Additionally, it has an auto-calibrating sensor, which makes its operation seamless.

Important Specs

Not only is this heater functional, but it’s also very stylish and sleek. This model comes with integrated Wi-Fi controls and a glass front. You can even install its app on your smartphone or tablet to wirelessly control the temperature and recirculation pump.

Durability

The heat exchanger warranty is for a whopping 15 years, while other parts have a five-year warranty, and the reasonable labor warranty is for one year. In terms of the warranty, this is the best tankless natural gas water heater.

Special Notice

There are different iterations of the Greentherm 9000 for residential or commercial use, so make sure to consult a contractor about your needs so they can suggest the right fit. 

Pros:

• Seamless operation and setup
• Long-lasting warranty for reassurance
• Clever, high-quality design

Cons:

• Could be pricey due to high-end features

Overview

The Titan N-120 made our list of the best tankless water heater choices in 2021 because it’s truly the best buy option. Even considering its fair price, the company offers a month-long return warranty. There’s a free USPS shipping special included with the purchase, meaning the product will only take up to three business days to reach you.

Durability

You get a 10-year warranty for the casing and a one-year warranty for the parts. In terms of protection, you’ll also get a dual Microtemp thermal fuse and a manual resettable thermostat. 

Important Specs

Other electric tankless water heater reviews note that the temperature rise decreases drastically as the flow increases, going from an 81° F rise at 1 GPM to 20° F at 4 GPM. This is actually a positive feature—it means the water heater is conserving energy while providing a sufficient GPM for a smaller household, or separate unit needs.

Its available voltage goes from 220 to 240 Volts, the maximum wattage is 11.8 kW, and the max amperage is 54. Neither the voltage nor the amperage should be an issue in an average household. But these specifications are there to let you make any necessary adjustments. However, it’s advisable to put an electric tankless water heater on its own circuit or circuits.

It’s the best RV tankless water heater, but you can also install it in a house or condo. This model is what an average home needs—it’s incredibly popular, cheap, and useful. Its energy efficiency is 0.99, which is exceptionally high for this price range.

Pros:

• Among the cheapest on the market
• Safe, efficient, and durable
• Ideal for an average household

Cons:

• Not the prettiest design

Overview

Eco Touch isn’t necessarily the best tankless water heater brand. However, it’s worth considering for smaller households and those with limited hot water needs. 

The Eco Touch ECO90 is a perfect point of use water heater for kitchen or bathroom sinks. Its modern design fits into any stylish home, whether you choose the black or white model. 

Important Specs

The optimal energy efficiency of this device is a whopping 99.8%. The electricity bill reduction alone is worth this investment. It’s so effective because of the smart power adjustments, which decrease with the water flow.

Speaking of this powerful element, it can heat water at 1.5 GPM, from 67° F to 106° F. The device’s voltage is 240 V, the wattage is 9 kW, and the maximum amperage is 37.5 Amperes.

Durability

This final entry on our best tankless hot water heater list provides perfect hot water, but not too hot, and of course, it’s designed to avoid flashes of cold water. The lifespan of this point of use tankless water heater is extended with the anti-corrosion build in the heating element. 

Pros:

• Safe and built to last
• Intelligent design for self-regulation
• Perfect for sinks, dishwashers, or washing machines

Cons:

• Eco Touch doesn’t have an official website

Picking the very best tankless water heater in 2021 is no joke. It’s a big investment, at least if you’re looking for a powerful unit that will last up to two decades. Of course, there are also budget options that can do the job just fine.

Here are some of the crucial selling points that made the products we chose rank higher than the others on the market:

Material Quality

Quality is always essential if you want a product that will last. That’s why some top-tier products can be quite expensive. They use stainless steel for the cover and copper alloy for the heating element.

Some cheaper materials can work as well, but these provide the best efficiency and durability. Skimming on the best outdoor propane tankless water heater, for example, can be very dangerous. With this in mind, we suggest these materials for your safety, not just the longevity of the heater.

In other words, getting a tankless water heater from Home Depot, or a similar store, without thoroughly investigating its materials is not so wise. 

Total Gallons per Minute

Our list features tankless water heaters with a wide variety of flow rates, i.e., GPM. If a device has a higher flow rate, it can support higher demand. So if you have a big house and many family members, we suggest getting a high-GPM heater. It’s the best tankless water heater for a large family.

This would be about 9.5 GPM, for reference. However, even 7 GPM could be enough, depending on your needs. Some point of use heaters have a very low GPM, but that doesn’t mean they’re faulty. They just have limited use, such as supporting sinks or dishwashers.

Temperature Rise

The best tankless water heaters with gas generally have higher temperature rise capabilities, but this doesn’t mean they’re always a better choice. You should look for a unit that has about 60° F temp rise capability.

Temperature control is just as important, and the best devices reduce the temperature with the flow reduction. More energy is conserved this way, and you don’t end up getting burned when taking a shower, for example.

Energy Efficiency

Energy efficiency is one of the critical factors when choosing the best tankless water heater. Tankless heaters are almost always more efficient than heaters with a tank. They’re built to conserve energy and reduce electricity bills.

The electric heaters are also more eco-friendly since gas heaters emit gases that are bad for the environment. Conversely, gas heaters are more powerful, so it’s a trade-off.

Warranty

Warranties are essential for any significant investment, and they reassure customers that they’ve made a safe choice. The longer the warranty, the better the investment.

We purposely chose products with very long warranties. These products also come from reputable, well-trusted brands. Some of the cheaper units don’t have extended warranties, but they’re still a good investment.

Buying, Installation, and Servicing Costs

Getting the best tankless hot water heater usually doesn’t come at a one-time price. It can also require a professional installation, which can be pricey. Furthermore, they’ll need servicing, which adds to the cost.

The most expensive units on the market are mostly gas tankless water heaters. They cost a lot and need regular servicing, but they pack the most heat. With such a device, you can supply a massive household with endless hot water.

Electric water heaters are a bit more practical, are easier to install and maintain, and have cheaper up-front costs.

Buying a tankless water heater is no small investment. As such, it should be researched and thought out. We’re here to help you find all the answers in one place and make the right call. 

If you’ve never had the chance to use a tankless water heater, don’t worry. The following sections will explain the essential characteristics and details you need to know. 

Note that some of these virtual characteristics were used as determining factors in our top 10 best tankless water heaters’ reviews. So it’s essential to know their impact on our decisions.

How Does a Tankless Water Heater Work?

Even though their design is intuitive and smart, tankless water heaters operate simply. Basically, they heat your water without using a tank. When the hot water tap is enabled, the water heater transfers cold water through a pipe directly into its unit. Then, the electric or gas unit heats the water.

This way, there’s always hot water, and you don’t have to wait for the tank to fill. It’s elegant and practical, but it has a few drawbacks.

Flow Rate

The flow rates of the best tankless water heaters on the market vary. In general, heaters that operate on gas have higher flow rates than those that work on electricity. 

The hot water flow rate is usually capped at 8 gallons a minute, but it can be as low as 2 gallons a minute. Even the largest gas models sometimes can’t supply an entire household, if it’s a big one.

When hot water is used only in one place, these heaters are great. However, if you use it, for example, for your shower and to wash the dishes simultaneously, it can be problematic. 

Temperature Control Capabilities

Besides providing more gallons of hot water per minute, the best gas tankless water heater also has a higher temperature rise capability. They can produce a 70° F temperature rise with a 5 GPM flow rate.

The optimal temp rise capability is about 60° F, or higher, depending on the household’s needs.

Gas vs. Electric

We’ve already touched upon this division. As you’ve noticed, gas water heaters pack a punch, but this comes at a cost. They harm the environment due to gas emissions. However, their differences are not as drastic when comparing a tankless water heater vs. a tank heater.

Electric tankless water heaters are more energy-efficient. This translates to increased savings, and they usually make a smarter investment in the long-term. Even though we said that gas heaters generally have better flow rates, this isn’t always the case.

Both types of heaters are excellent and have their pros and cons. However, gas systems are more costly, can be more difficult to maintain, and have shorter warranties and service lives. 

Indoor vs. Outdoor

This tankless water heater distinction is self-explanatory, but let’s elaborate on it for the best tankless water heater reviews. Outdoor units are more durable because they have to endure the elements. Still, you should use caution if you live in extreme living conditions—indoor heaters are better options in this case.

However, outdoor heaters have some advantages over indoor heaters. First, they don’t need specialized venting. This is a must for indoor heaters because condensation should never come into contact with the heater. In other words, you need additional pipes and drains. Put simply, plumbing is much simpler with outdoor water heating systems.

Setting up an indoor unit works much better in new homes because adding it later can affect many things and alter a home’s infrastructure. Overall, an indoor unit will be safer than an outdoor tankless water heater because it’s protected from any extreme weather conditions. As such, it’s a more secure long-term investment.

Whole House vs. Point of Use

A tankless water heater for the whole house will, unsurprisingly, supply the entire house with hot water. Point of use tankless water heaters only provide hot water to a specific outlet or location in the house. For example, it can supply only the bathroom—or even just the shower.

Point of use heaters need to be near the outlet they supply. In most cases, these will be electric tankless water heaters, and they have vertical or horizontal mounts.

Advantages

The main benefits of a tankless water heater are as follows:

• Tankless water heaters are energy-efficient, i.e., they pay off in the long run.
• They are very durable, meaning they last a long time.
• Because they lack a tank, they use up less space than water heaters with tanks.
• You can never run out of hot water when using this heater.
• They’re ecological—at least the electric ones are.
• Some of these units net you a substantial federal tax rebate.

Disadvantages

Nothing in life is perfect, and neither are water heaters without a tank. Here are their main drawbacks:

• Tankless water heater prices can be high.
• They might need an additional electrical circuit if they’re electric, or they might require an added natural gas line if they run on gas.
• Heaters running on gas emit greenhouse gases.
• Tankless heaters can potentially expend a large amount of gas or electricity.
• Water waste might increase due to the time necessary to heat the water.
• Gas tankless water heaters need yearly servicing. 

Wrapping Up

Choosing the best tankless water heaters is not simple, but hopefully, we made the job easier for you. If you want to conserve energy, space, and time, then a tankless water heater is the right choice. They bring many benefits to the table, and they’re well worth the investment. 

Once you go tankless, it’s hard to imagine ever going back. This article should answer all your burning questions and help solve any dilemmas as you look for the right water heater for your family.

Some of the most common questions are answered below.