Never Run Out of Hot Water Again with These Top Tankless Water Heater (2024)

Our Top Picks

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. 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 (no vent is required).

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 (which reads on an electronic display) to as high as 140 degrees F, but higher temperatures reduce the flow rate. In addition, Jeremy Jones, electrician and owner of BJ Electrical Service in Florida, points out that most people should set the temperature between 110 and 120 degrees F for the sake of safety.

This model retails for under $650, which is a good value when you consider its performance and long-term savings from its energy efficiency. A 5-year warranty for heating elements is included as well.

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

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, basem*nt, or crawl space. It's 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. It does however offer a 12-year warranty on the heat exchanger, and 5- and 1-year warranties for labor and parts, too.

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.

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

A tankless water heater can be a smart upgrade for your home, paying off in energy savings and convenience. And, if you shop for a budget option, like the EcoSmart ECO 2, you can maximize your savings while minimizing your spending.

This electric tankless water heater supports a flow of 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 it does fall 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.

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

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 (the least on our list), which is still 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.

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

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. 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.

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

While you can expect to see energy savings with any tankless water heater, the Stiebel Eltron brand rates its Tempra 36 Plus as one of its most energy-efficient units. 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.

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

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 basem*nt 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.

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

The compact EcoSmart ECO 11 covers all the bases for a tankless water heater for an RV. Its small 3.75 x 8 x 11.5-inch footprint and 6.5-pound weight assures it can be easily mounted in tight spaces, which is ideal for installation in an RV, mobile home, or tiny house. This electric model requires no venting and carries a limited lifetime warranty on the stainless steel heating elements.

In keeping with its small size, the ECO 11 tankless water heater doesn’t have the most powerful flow rate, topping out at 3.1 GPM. But it's sufficient to support at least one shower, as long as the groundwater temperature is above 62 degrees Fahrenheit. As other EcoSmart models, you can set the temperature of your water supply from 80 to 120 degrees Fahrenheit using the digital temperature control feature.

_{Fuel Type: Electric | Wattage: 13,000 watts | Flow Rate: Up to 3.1 GPM | Heating Power: 11 kilowatts}

A large home has the potential for more fixtures to be turned on simultaneously, so you should choose a tankless water heater with an increased flow rate to meet the demand. The Rinnai RU199iN is a high-efficiency natural gas water heater that delivers hot water at a flow rate up to 11 GPM (the highest on this list). It’s a popular choice as a tankless water heater for large homes and worth considering if you frequently place many demands on your hot water supply (like, say, you don’t want to wait on the dishwasher or washing machine to finish a cleaning cycle before taking a hot shower).

With these specifications, this Rinnai model can support up to three showers, sinks, or appliances simultaneously. But as temperatures increase, this tankless water heater can easily support four to seven fixtures at once.This is a condensing natural gas tankless water heater, which is more energy-efficient than non-condensing models. So it’s no surprise that the Rinnai RSC199iN is Energy Star-qualified and has an impressive Uniform Energy Factor (UEF) rating of 0.95.

While the initial cost of this high-capacity condensing tankless water heater is higher than that of a basic non-condensing water heater, we believe it's worth it for this product, which offers impressive flow rates along with lower energy usage to offset the higher price point.

_{Fuel Type: Natural Gas | Wattage: Not Listed | Flow Rate: Up to 11 GPM | Heating Power: 199,000 BTU}

Final Verdict

For an electric tankless water heater, we recommend the Rheem Performance RETEX-36. 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 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.

FAQ

• 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.

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