The 7 Best Tankless Water Heaters for 2023

The Rheem Performance Tankless Water Heater is our top pick

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The Spruce / Lecia Landis

Tankless water heaters offer efficient, energy-saving alternatives to conventional water heaters with storage tanks. Instead of storing and heating water in anticipation of demand, tankless water heaters generate warm water as needed. Also referred to as instant water heaters, these appliances save space while ensuring that you never run out of hot water while showering, washing your hands, doing dishes, or doing any other household task.

Having said that, a tankless water heater can't help your household do all those things at once! Jeremy Jones, electrician and owner of BJ Electrical Service in Bradenton and Sarasota, Florida, points out that gas and electric tankless heaters can only sufficiently heat a set flow of water at any given time. "So there are limits on how many plumbing fixtures can get hot water at the same time while maintaining sufficient water pressure," he says. This is why you frequently see the flow rate, measured in gallons per minute (GPM), listed prominently in the product details. The flow rate can tell you definitively how much water a specific fixture is using.

A quality tankless water heater is space-saving and energy-efficient, heating only as much water as you need at any given time. We researched dozens of tankless water heaters, evaluating efficiency, flow rate, temperature control, ease of installation, and value.

Our Top Picks

Best Electric

Rheem Performance 7.03 GPM Tankless Electric Water Heater

Rheem Performance 36 kw Self-Modulating 7.03 GPM Tankless Electric Water Heater


What We Like
  • Wide water temperature range

  • 5-year warranty on heating elements

  • Electronic temperature control and display

  • Vent-free installation

What We Don't Like
  • Not compact for point-of-use installation

  • Requires complex wiring

We recommend the Rheem RETEX-36 as the best electric water heater because it offers a generous flow rate, up to 7.03 GPM, and supports hot water for simultaneous multiple fixtures. Part of the Rheem Performance series, this tankless electric water heater saves on space without sacrificing effectiveness. It also has a 99.8 percent efficiency rating, according to the manufacturer. Installation requirements include space for the unit, which measures 18.25 x 21.625 x 3.5 inches, and wiring to four 40-amp double pole breakers.

This electric tankless water heater can supply water, simultaneously, to five showers and two sinks, at 105 degrees F, depending on your incoming water temperature. Most households should have no problem relying on this as a whole-house tankless water heater, since it can still supply two showers and two sink fixtures with hot water when the groundwater temperature is as low as 37 degrees F.

You can adjust the water temperature output to as high as 140 degrees F, but higher temperatures reduce the flow rate. In addition, Jones points out that most people should set the temperature between 110 and 120 degrees F for the sake of safety.

This model retails for about $650, which is a good value when you consider its performance and long-term savings from its energy efficiency.

Price at time of publish: $650

Fuel Type: Electric | Wattage: 36,000 | Flow Rate: Up to 7.03 GPM | Heating Power: Not listed

Best Natural Gas

Rinnai RL75iN High-Efficiency Plus

Rinnai RL Series HE+ Tankless Hot Water Heater


What We Like
  • 12-year warranty on heat exchanger

  • Can be installed in a basement, crawl space, or attic

  • Wi-Fi compatible for remote monitoring

What We Don't Like
  • Only suitable for indoor installation

  • Additional components required for recirculation

The Rinnai RL75iN is our pick for a natural gas tankless water heater since it offers reliable performance, impressive heating capabilities, and the ability to be installed in just about any indoor space, including an attic or crawl space. The Japanese manufacturer of water heaters is frequently praised for its reliability, and it doesn’t hurt that the heat exchanger on the RL75iN carries a 12-year warranty.

This model is capable of a maximum flow rate of 7.5 GPM and generates 180,000 BTU of heating power. For climates with groundwater temperatures from 47 to 67 degrees F, the RL75iN can keep water flowing to three or four fixtures at the same time.

While this model is compatible with Rinnai’s Re-Circ technology, you need to purchase additional components to take advantage of the hot water recirculation feature, which slowly and constantly circulates the water in the hot water pipes back into the water heater for reheating. It’s something to consider, since a common complaint about this model is it wastes a fair amount of water before sufficiently heating up sink or shower water.

Its compatibility with home Wi-Fi networks means it’s easier to control and monitor, even if you install it in an out-of-the-way location. If that feature is important to you, you need to purchase a separate control module.

Despite the prospects for adding to the listed price, we still recommend the Rinnai RL75iN as a top-performing natural gas tankless water heater and a worthwhile upgrade if you need to supply piping-hot water to multiple fixtures.

Price at time of publish: $1,130

Fuel Type: Natural gas | Wattage: Not applicable | Flow Rate: Up to 7.5 GPM | Heating Power: 180,000 BTU

Best Budget

Ecosmart ECO 27 Electric Tankless Water Heater

Ecosmart ECO 27 Electric Tankless Water Heater


What We Like
  • Limited lifetime warranty on heat elements

  • Flow rate up to 6.5 GPM

  • Flow sensor to maintain operation

What We Don't Like
  • Maximum temperature of 140 degrees F

  • No Wi-Fi integration

A tankless water heater can be a smart upgrade for your home, paying off in energy savings and convenience. You can maximize your savings while minimizing your spending if you shop for a budget option, which costs around $500 for a tankless electric model that can support an average household of three to four people. We recommend the EcoSmart ECO 27 as an affordable choice for an instant water heater.

This electric tankless water heater supports a flow up to 6.5 GPM and has self-modulating heating technology to keep water temperatures consistent. Instead of a flow switch, as you’d find on some tankless water heaters, the EcoSmart ECO 27 uses a sensor. This prevents a burst of cold water if water pressure drops while the unit is heating.

Temperature settings for this model range from 80 to 140 degrees F, which is plenty of heating power for most applications. But that falls short of the maximum 160 degrees F some tankless water heaters are capable of.

The EcoSmart is compact and doesn't take up much room when installed since it measures 17 inches tall and wide and only weighs 14 pounds.

If you’re looking for a space-saving alternative to a conventional water heater but need a tankless version that is easy on the wallet, the EcoSmart ECO 27 is a solid pick in terms of purchase price and long-term energy savings.

Price at time of publish: $407

Fuel Type: Electric | Wattage: 27,000 watts | Flow Rate: Up to 6.5 GPM | Heating Power: Not listed

Best Point-of-Use

Rheem 240V Heating Chamber RTEX-13 Residential Tankless Water Heater

Rheem 240V Heating Chamber RTEX-13 Residential Tankless Water Heater

Courtesy of Walmart

What We Like
  • Fits under sinks or in closets

  • Electronic temperature control

  • Relatively simple wiring

What We Don't Like
  • Only 5-year heat exchanger warranty

A point-of-use tankless water heater is a good choice if you need to ensure that a specific fixture in your home has a ready supply of hot water at all times. This type of water heater is usually installed close to the fixture it supports, such as under a sink cabinet or near the primary shower. For that type of tankless water heater, the Rheem RTEX-13 is a popular pick that provides instant hot water.

This small tankless water heater delivers up to 3.17 GPM, which is more than sufficient to supply a single fixture. It measures 12 inches high and 8.25 inches wide, so it’s compact enough to be installed inside a bathroom vanity or closet. Its electronic temperature control gives you the option to set the water temperature in 1-degree increments, from 80 to 140 degrees F.

The only downside to this affordable, electric point-of-use instant water heater is its 5-year warranty on the heat exchanger, which isn’t as long as the warranty period on some other models. Also, this unit only requires wiring to a single 60-amp double pole breaker. But we strongly recommend that you secure professional installation.

Price at time of publish: $330

Fuel Type: Electric | Wattage: 13,000 watts | Flow Rate: Up to 3.17 GPM | Heating Power: Not listed

Best Propane

Rinnai V53DeN Outdoor Tankless Water Heater

Rinnai V53DeN Outdoor Tankless Water Heater


What We Like
  • Performs as low as minus-4 degrees F

  • Also natural gas capable

  • 10-year warranty on heat exchanger

  • Flow rate of 5.3 GPM

What We Don't Like
  • Temperature controller sold separately

While most tankless water heaters are installed inside your home, installing one outdoors avoids having to rip out drywall, reroute gas lines, and vent the unit. Also, some basements are just too small to accommodate an installation. If you want to go the outdoor route, you should only purchase a tankless water heater designed for outdoor installation.

We recommend the Rinnai V53DeP, a whole-house tankless water heater that has the features and durability needed for outdoor installation. It’s not as powerful as some other tankless water heaters but is sized right for small to medium homes. The unit's maximum flow rate is 5.3 GPM, and it can support two showers simultaneously in most conditions.

This model uses liquid propane as a fuel source but can be converted to natural gas. (If your home lacks a natural gas line, you need to have one installed.) In either case, venting is usually required, according to Jones, and for this reason, these types of units are often installed outside the house.

Another key feature that qualifies the Rinnai V53DeP for use as an outdoor tankless water heater is its anti-freeze protection. The unit should continue to function in cold weather conditions, even as low as minus-4 degrees F.

The manufacturer recommends that for cold-weather climates, you also install an optional drain-down system to ensure that water inside the unit can drain if there’s a power failure, gas outage, or component failure. You also should ensure that it is protected from direct wind exposure.

Price at time of publish: $620

Fuel Type: Natural Gas | Wattage: Not applicable | Flow Rate: 5.3 GPM | Heating Power: 120,000 BTU

Best Energy Saving

Stiebel Eltron Tempra 36 Plus Whole House Electric Tankless Water Heater

Stiebel Eltron Tempra 36 Plus Tankless Water Heater


What We Like
  • 99 percent energy efficient

  • Extremely quiet operation

  • Maintains steady output temperature

  • Minimum 68 degrees F

What We Don't Like
  • Requires 300 amp electrical service

Tankless water heaters offer significant savings on energy costs when compared with conventional water heaters, Jones says. “Rather than slowly heating and then storing water for use, a tankless water heater heats very quickly and only when there is a demand for hot water,” he explains.

While you can expect to see energy savings with any tankless water heater, Stiebel Eltron rates its Tempra 36 Plus as one of its most energy-efficient units. (This is a manufacturer estimation: Energy Star doesn’t issue energy factor ratings for electric tankless water heaters.) It offers up to 7.5 GPM of hot water to three or more fixtures, and operates with virtually none of the noise associated with water heaters, according to the manufacturer.

Some tankless water heaters are known for reducing the temperature when another tap is turned on. The Tempra 36 Plus eliminates this "cold water sandwich" with an advanced flow control feature that reduces the flow of water by a marginal amount if the demand for hot water increases. This allows the heater to maintain the output temperature, so you don’t wind up with a cold burst of water in your shower, sink, or anywhere else the tap is turned on.

A frequent complaint of instant hot water heaters is the water gets too hot, too soon. However, with a minimum temperature setting of 68 degrees F, this Stiebel Eltron model has one of the lowest temperature thresholds of tankless water heaters.

Installing this unit requires 300 amp electrical service; consult an electrician to see if your home’s electrical panel is properly equipped before purchasing this powerful electric tankless water heater.

Price at time of publish: $810

Fuel Type: Electric | Wattage: 36,000 watts | Flow Rate: Up to 7.5 GPM | Heating Power: Not listed

Easiest to Use

Rheem’s 18kW Tankless Electric Water Heater

Stiebel Eltron Tempra 36 Plus Tankless Water Heater


What We Like
  • Digital display with control knob

  • 1-degree temperature increments

  • Minimal installation requirements

What We Don't Like
  • No freeze protection

A tankless water heater offers efficiency and simplicity. We believe the easiest to use is the Rheem Performance tankless water heater. You can adjust the water output temperature in 1-degree increments with the sleek control knob on the front of the unit, and verify it’s set correctly by checking the digital display. You can adjust the target temperature any time you like. 

This model, which has a flow rate up to 3.51 GPM, is small enough to be installed for point-of-use applications. Or it can be installed in other locations such as a basement or attic. Keep in mind that it’s not impervious to freeze damage, so it shouldn’t be installed anywhere that temperatures may fall below freezing.

As an electric tankless water heater, installation is straightforward. The manufacturer recommends professional installation, but it’s worth knowing that this model is ventless and requires only a connection to two 40-amp double pole breakers.

Price at time of publish: $425

Fuel Type: Electric | Wattage: 18,000 watts | Flow Rate: Up to 3.51 GPM | Heating Power: Not listed

Final Verdict

For an electric tankless water heater, we recommend the Rheem Performance RETEX-36. It's a capable, efficient tankless water heater with electronic temperature control and a convenient display. It delivers up to 7.03 GPM, which is plenty of capacity, even for a large household that requires hot water from multiple fixtures at once. If you’re shopping for a natural gas tankless water heater, check out the Rinnai RL75iN. Its maximum heating power is 180,000 BTU, and it is sufficient to supply at least three or four showers with hot water. For added convenience, it is Wi-Fi compatible, making it a good pick for a smart home. For the best propane-fuel tankless water heater, we recommend the Rinnai V53DeP, a whole-house tankless water heater that has the features and durability needed for outdoor installation. Its maximum flow rate is 5.3 GPM, and it can support two showers simultaneously in most conditions.

What to Look for in a Tankless Water Heater


There are two basic types of tankless water heaters to consider: whole-house and point-of-use.

  • Whole-house models have flow rates substantial enough to support multiple fixtures simultaneously. Although the number of fixtures may vary significantly, based on the temperature rise and the flow rate of the fixtures, many whole-house tankless water heaters are designed to support at least three fixtures at once under most conditions.
  • Point-of-use water heaters are usually electric and heat up water as needed for a sink, a shower, or other single fixture. Their compact size makes them suitable for installing underneath a cabinet or in a closet, close to the fixture being supplied with hot water. They also have small storage tanks, which makes them less energy efficient.


Before delivering hot water to your showers, sinks, or appliances, a tankless water heater must first warm the water to your preset temperature. To heat the water, tankless water heaters rely on fuel sources such as natural gas or propane, or heat water electrically by being hardwired to your home’s electrical system.

If your home is already equipped with a natural gas line or a propane tank, it makes the most sense to replace the water heater with the same type of unit. The same is true if you replace an existing electric water heater.

The differences among natural gas, electric, and propane water heaters can be summed up this way:

  • Natural gas tankless water heaters offer high-capacity flow rates and are good choices for large households. Usually, they cost less to operate than propane or electric units. However, they frequently carry high initial costs, which may include installing a gas line if none exists.
  • Electric tankless water heaters cost more at the purchase point than natural gas units. But this differential can quickly disappear if you need to install a natural gas line. Also, electric tankless water heaters are usually about 10 percent more efficient than natural gas models.
  • Propane tankless water heaters are often used if the homeowner wants the unit outdoors, or for an RV or motor home. Because propane can be expensive, these units frequently cost more to operate than natural gas or electric tankless water heaters.

Flow Rate

The flow rate of a tankless water heater is measured in gallons per minute (GPM). This is important to consider when picking the right size water heater for your house since it determines how many fixtures the water heater can supply simultaneously.

Flow rate is impacted by the temperature of incoming ground water and the "rise"—the difference between the groundwater temperature and the target temperature you set for your tankless water heater. As the rise increases, the heater's flow rate decreases. “Imagine the difference between trying to heat water from the ground during the summer versus the winter," Jeremy Jones, electrician and owner of BJ Electrical Service in Bradenton and Sarasota, Florida, says. "The starting point of the temperature of the water will absolutely affect how much water can be heated and how quickly.”


Size comes into play in two important ways: It impacts the flow rate and determines installation options.

Larger tankless water heaters deliver more water. Smaller tankless water heaters may not output as much hot water per minute, but they can be installed in tighter spaces. Point-of-use tankless water heaters are the smallest instant water heaters. They typically are installed in bathroom vanity cabinets or underneath kitchen sinks to provide a boost of hot water to a single fixture.

  • What size tankless water heater do you need?

    Size doesn't matter if you're shopping for a point-of-use tankless water heater to supply hot water to a single fixture such as a shower or bathroom sink. However, it does make a difference when considering a whole-house unit. In that case, your primary concern should be flow rate, as measured in gallons per minute (GPM). To determine how many GPM you need for your home, add up the flow rate of the fixtures or appliances you’re most likely to use simultaneously. This tells you the target flow rating.

    Since tankless water heaters are significantly smaller than conventional water heaters, physical dimensions are usually less important in choosing the water heater. However, this can come into play if you work with very specific installation requirements such as in an RV, or if you need to install a tankless water heater in a home's closet or other confined space.

  • Is a tankless water heater efficient?

    When compared with conventional water heaters with storage tanks, tankless water heaters are more efficient. As Jones points out, “A lot of energy is used but only for a brief amount of time, so they are more efficient than slowly heating and reheating water in a tank.”

    To compare the efficiency of water heaters, look for the unit’s energy factor rating. Energy Star uses a metric known as the Uniform Energy Factor criteria. According to Energy Star, the higher the UEF, the more efficient the water heater. Many water heaters with storage tanks have UEF ratings ranging from 0.60 to 0.85, although some high-efficiency electric water heaters may have UEF ratings of 0.90 or above. 

    Note that Energy Star does not have UEF ratings for electric tankless water heaters. If energy efficiency is your primary concern, Jones says, “Generally, electric tankless are considered more efficient than gas, and both are more efficient than a conventional tank.”

  • Do tankless water heaters need venting?

    Electric tankless water heaters do not need venting, but this usually is required for gas or propane units. There are two types of vented tankless water heaters: non-condensing and condensing.

    • Non-condensing tankless water heaters release steam or water vapor immediately. This type of water heater usually costs less to purchase, but the ventilation materials may cost more because they need to handle the high temperature of the released steam. These models typically have low efficiency ratings, in the range of 0.80 to 0.85, because the released steam translates into lost heat. 
    • Condensing tankless water heaters are more energy-efficient than non-condensing units and more cost-effective in the long run. They also are usually more expensive to purchase initially. This type of water heater captures the steam using a condenser, reusing the heat before venting the exhaust. Efficiency ratings for condensing tankless water heaters are about 0.98. Also, the lower temperature of the exhaust brings about a savings in the cost of ventilation materials required for safe operation.

Why Trust The Spruce?

This article was researched and written by Erica Puisis, a writer and product tester specializing in large and small home appliances, home improvement features, and plumbing fixtures. Since 2017, Puisis has been writing for The Spruce about everything from home saunas and infrared heaters to water softeners. To choose the best options for this article, she compared products' flow rate, heating power, and energy efficiency. She also evaluated each model's installation requirements, along with features such as recirculation technology and Wi-Fi compatibility.

Puisis also interviewed Jeremy Jones, electrician and owner of BJ Electrical Service in Bradenton and Sarasota, Florida. Jones provided information on the advantages and efficiency of tankless water heaters and how to choose the right one for the needs of your home.

Updated by
Timothy Dale

Timothy Dale is a home repair expert and writer with over a decade of hands-on construction and home improvement experience. He is skilled in residential, commercial, industrial and institutional plumbing, electrical, carpentry, installation, renovations, and project management.

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