No matter the type of house you have, you want to be able to enjoy hot water. The traditional method would be with a water heater that features a tank, but many homes now use tankless water heaters.

But which is the best tankless water heater? And how do you know which one to select? We’ve compiled all the information you need to know about tankless water heaters and choosing the right one. After going through the basics and some general advice for choosing your appliance, we’ll take a look at our picks for the best tankless water heaters in 2021.

The Top 8 Tankless Water Heaters in 2021

With all that background in mind, here are our picks for the best tankless water heaters in 2021. Any of these units would be a great addition to your home, and we included tankless water heater reviews to help you choose. Use the above criteria to decide which one is best for your needs, adding your rating to ours.

1. EcoSmart ECO 18 Electric Tankless Water Heater


Key Features

  • 1.8 – 4.3 GPM
  • 17 x 14 x 3.75 inches
  • Electric


  • Compact size
  • Temperature control
  • Field-replaceable elements


  • Some homes require a larger unit

EcoSmart prides itself on delivering “endless hot water” while saving time, money, and space. Compared to a traditional storage-tank water heater, the EcoSmart ones, including this appliance, are 90 percent smaller. As for fuel type, it is one of the electric tankless water heaters.

To help you save energy, EcoSmart ECO units have self-modulating technology that allows them to use the minimum amount of energy to heat the water. The system also remains off unless you need hot water. They can also save as much as 50 percent on the energy costs of heating water, thanks to reducing heat loss. This appliance also puts you in control of the temperature, letting you adjust it from 80 to 140 degrees Fahrenheit. Maintenance is easier and less expensive, thanks to field-replaceable elements, improving the client rating of this unit.

This best tankless water heater, the ECO 18, features 18-kilowatts of power. Its flow rate is 1.8 to 4.3 gallons per minute, with variations depending on the water temperature control settings. It has the standard voltage of 240 and requires two 8 AWG cables and two 40A DP breakers. The maximum amperage is 75, and it uses a ¾-inch NPT water connection.

Thanks to its flow rate, you can run a shower and a sink in most climates and two simultaneous showers in warmer climates. This should be enough water heating for most homes.

For those concerned about size, this unit weighs 11.25 pounds and measures 17 inches by 14 inches by 3.75 inches. The brand also has the popular EcoSmart ECO 27. That EcoSmart ECO 27 is larger than this ECO 18.

2. Rinnai RUC98iN Ultra Series Indoor Natural Gas Tankless Water Heater, Twin Pipe


Key Features

  • Runs on natural gas
  • 18.5 x 26 x 10 inches
  • 199,000 maximum BTU


  • 12-year warranty
  • Ultra-low NOx emissions
  • Residential or commercial
  • 9.8 GPM


  • Commercial controller sold separately
  • 9.8 GPM rate only applies in warmer climates

This is a natural gas tankless water heater that is designed only for use inside. The design was engineered to save space. This helps ensure that you have enough room to install the unit inside.

The Rinnai heater has a temperature range of 98 degrees Fahrenheit to 140 degrees for residential use and 98 degrees to 185 degrees. You would, however, have to buy the commercial controller separately. You can use this unit with any of the Rinnai digital controllers.

Compared to other natural gas units, it has ultra-low NOx emissions. Other technical details include its weight of 61.7 pounds and dimensions of 18.5 inches by 26 inches by 10 inches. Both the gas and water connections are 3/4 inches.

The Rinnai non-tank heater has an energy factor rating of up to 0.96 and a uniform energy factor of up to 0.92. It also has a maximum of 199,000 BTU. This Rinnai heater also features 95 percent thermal efficiency with the option to use either propane or natural gas.

To improve its value, even more, this Rinnai heater has a 12-year warranty for the heat exchanger, as well as five years for parts and one year for labor, assuming you use it in a residential building.

3. Bosch Electric Mini-Tank Water Heater Tronic 3000 T 4-Gallon


Key Features

  • Electric
  • Point-of-use heater
  • 13.75 x 13.7 x 13.5 inches


  • 98% thermal efficiency
  • 6.8 GPM
  • Simple maintenance


  • Not for whole house use

This is the 4-gallon version of the Bosch Mini-Tank tankless water heater, and a 2.5-gallon version is also available. This is designed to be a point-of-use system, hence its smaller size. It was engineered to easily fit under a sink or in a similar location, thanks to its dimensions of 13.75 by 13.75 by 13.5 inches.

The point-of-use system is designed for one of three purposes. You can use it as a sink’s sole heating source, a buffer to complement a tankless system with intermittent cooler water (cold water sandwiching), or to supplement a heater that is too far from the sink.

The system has a quick recovery rate, as you can get hot water on demand. The hot water heater can supply two sinks simultaneously. The recovery rate at 90 degrees is 6.8 GPM. Expect a temperature range of 65 to 145 degrees and a water pressure range of 150 psi.

The unit has a high thermal efficiency of 98 percent for reduced energy costs. Other important specs include 120 volts and 12A amps. That 120-volt requirement comes from the 36 to 37-inch cord. This helps with the unit’s flexibility. It is also easy to mount, thanks to an included bracket for wall-mounting or the ability to place it on the floor. The water fitting is a ½-inch male NPT.

Bosch Electric designed this tankless water heater to be simple to maintain, thanks to its glass-lined material. The system also has CFDC-free foam insulation that is thick, helping to maximize its energy efficiency.

4. Takagi T-H3-DV-N Condensing High Efficiency Natural Gas Indoor Tankless Water Heater


Key Features

  • Runs on natural gas
  • 10 GPM
  • Up to 199,000 BTU


  • Computerized safety
  • Can heat up to four bathrooms
  • Improved heat transfer compared to stainless steel
  • Energy Star certified


  • Expensive

This Takagi heater is compact and saves energy as well as space, especially compared to tank units the size of a large box. There is no pilot light to give you one less worry. There are also computerized safety features, including troubleshooting diagnostic codes and protection against surges, overheating, and freezing. The controls are conveniently integrated into the heater.

Emissions are not a concern, thanks to its ultra-low NOx emissions. The heater is also highly efficient thanks to the commercial-grade copper alloy in the primary heat exchange. This improves the heat transfer 25 times over stainless steel.

It comes standard with a power cord for easy installation and use. This heater can handle heating up to three baths if you are in a cooler climate or up to four bathrooms if you are in a warmer climate, assuming you have a natural gas input rating of 199,000 BTU.

The brand has a strong history, as the Takagi T H3 DV and H3 DV N are both popular tank heater options, as well.

5. Stiebel Eltron 224199 240V, 1 Phase, 50/60 Hz, 24 kW Tempra 24 Plus Whole House Tankless Electric Water Heater


Part of the popular Tempra line from Stiebel Eltron, this 24 Plus unit does not require any venting and has proven reliability. The company has been in the industry for more than 90 years, giving more confidence. You control the temperature of the unit with digital controls. It is one of the electric tankless hot water heaters on this list.

Stiebel Eltron says that the unit can save you 15 to 20 percent or more on the part of your electric bill related to hot water. This Tempra unit has a 99 percent energy efficiency rating. It also has intelligent technology that self-modulates to minimize energy use. There is also Advanced Flow Control to keep the temperature constant.

Like most of the other options on this list, it is sleek and compact, making it easy to fit wherever you need it. It is also silent even when in operation. For compatibility, it uses 240 or 208 volts, requires a minimum flow of 0.5 gallons per minute, and should be used with at least 150A in your home.

There is a 7-year warranty for leakage and a 3-year warranty for parts.

Key Features

  • 99% energy efficiency rating
  • Electric
  • 21.7 x 20.1 x 9.6 inches


  • 7-year warranty
  • Reliable company with 90 years of history
  • Can handle up to three showers


  • May only handle a shower and a sink in cooler climates

6. Stiebel Eltron Tankless Heater – Tempra 12 Plus


Key Features

  • 4.63 x 16.63 x 14.5 inches
  • Electric
  • Heats up to 140 degree


  • 7-year warranty
  • Budget-friendly
  • From reliable brand


  • Only good for small homes or as point-of-use
  • Can only handle one shower at a time

Similar to the Tempra 24 Plus already on this list, the Tempra 12 Plus has the Advanced Flow Control feature from Stiebel Eltron. This feature automatically keeps the water temperature consistent by slightly reducing the flow if the demand for hot water goes above the unit’s capacity.

You save space in your home with this tankless water heater, thanks to its small design. At the same time, it is eco-friendly, thanks to its auto modulation that saves energy, combined with the electronic control of water flow. For those who are switching to tankless heaters to save money on energy, the savings monitor is a great additional feature.

This system is easy to use, thanks to its digital temperature display, preset temperature buttons, and memory buttons. It operates silently for no disruption and uses an electronic switch to activate the unit.

As the Tempra 12 Plus, this unit uses 12kW and 240V. You should have an electric service that is at least 100A. Expect a temperature output between 68 and 140 degrees.

You get an even better value, thanks to the warranty on this unit. It includes seven years of protection against leaks and three years of protection for parts.

7. Eemax EEM24027 Electric Tankless Water Heater


Key Features

  • Electric
  • 5.3 GPM
  • 17 x 17 x 3.75 inches


  • 5-year warranty
  • Handles up to four showers
  • Self-modulating technology for efficiency


  • Some homes require higher GPM

This compact unit takes up minimal space in your home and delivers hot water continuously. The unit’s advanced self-modulation tech lets it adjust its energy use based on the amount of hot water you need.

The compact size means that the tankless water heater only weighs 13.75 pounds and measures 17 by 17 by 3.75 inches.

This particular tankless heater uses 27 kilowatts and 240 volts. It is designed to heat enough water for two sinks and one shower at the same time if you live in a colder area. If you live somewhere warmer, it can handle up to four sinks or showers simultaneously. Those who prefer a gas-powered heater should look at the other options on this list.

The warranty covers five years of leak protection and a year of protection on parts.

8. 18kW / 240V Electric Tankless Water Heater, ThermoPro Series with Digital Thermostatic Control


Key Features

  • 3.7 GPM
  • Electric
  • 17.38 x 5.25 x 13.38 inches


  • Can handle three applications simultaneously
  • Advanced self-modulating system to save energy
  • You control the temperature


  • Less GPM than some on the list
  • Not ideal for large homes in cool areas

This unit from the ThermPro series has up to a 3.7 GPM flow rate. It was designed to heat water that is just 37 degrees Fahrenheit when at 1.9 gallons per minute. The smart flow technology delivers unlimited hot water. Like many of the other units on this list, it features an advanced self-modulating system that regulates heating energy and water flow. That saves energy while reducing water consumption.

In a moderate or warm climate, you can use this ThermPro tankless water heater with as many as three applications, such as a shower, kitchen sink, and bathroom sink with a 73-degree inlet temperature, meeting your hot water needs.

You can use the convenient digital temperature control to choose a temperature between 90 and 135 degrees, with the option of one-degree intervals. Using this unit can save you as much as 50 percent on your electric bills over storage tank water heaters.

Keep in mind that this water heater requires three 30a single-phase DP breakers and three 8 AWG wires. It uses 240 volts and 0.75 amps.

To make the unit more durable, Atmor used stainless steel on the interior. In addition to improving durability, this improves corrosion resistance to maximize heat efficiency and the unit’s life expectancy.

What Is a Tankless Water Heater?

The name of these systems gives you a good idea of their most important factor, the lack of a tank. They are also called instantaneous or demand-type water heaters. These systems will only heat your water when the system requires it.

How Do Tankless Water Heaters Work?

Your tankless water heater will have a section leading cold water into the system and a section leading hot water out. When you turn on the hot water in your house, the cold water enters the unit, and a heating element of some sort will heat it. The heating element can be either electric or gas.

There are several types of tankless water heaters, so the exact steps that it follows to function will depend on whether it is gas or electric, the ignition type for gas tankless heaters, and a few other minor factors. That being said, the following is the general process for a typical gas-powered unit:

  • When you turn on your tap for hot water, the tankless water heater’s flow sensor detects the incoming water entering the heater.
  • The sensor lets the control panel start heating water.
  • The control panel activates the fan to draw in air. It also opens the gas valve to let in gas, igniting the burner.
  • The heat exchanger uses the flames’ heat to heat the water going through the tubing.
  • The unit’s mixing valve tempers water, which is superheated, as it leaves the exchanger.
  • The temperature sensor confirms the water’s temperature. If it is not right, the panel adjusts the mixing, flow-regulating water, and gas valves.
  • If the temperature is correct, it leaves the system.
  • A vent brings the exhaust gases away from the unit.

Pros and Cons of Tankless Water Heaters

With those basics in mind, take a look at some of the reasons that people opt for tankless water heaters and some of the reasons that people choose to stick to a traditional option with a tank.

Hot Water Right Away

Water heaters with a storage tank require you to wait a few minutes to get hot water. By contrast, you get water at the temperature you want immediately with an on-demand or tankless water heater.

The Heated Water Is Not Limitless – But There Are Workarounds

One important note is that with a tankless water heater, you can only get the hot water at a limited rate. This rate is measured as gallons per minute (GPM), and on average, you should expect about 2 to 5 gallons each minute.

Expect a higher flow rate if you get a gas tankless water heater than an electric one. No matter the heater, however, this style will not handle large households that use hot water in multiple areas at the same time. For example, you are unlikely to be happy if two people shower in separate bathrooms at the same time. Or it may be pushing it to run the dishwasher while someone showers.

The good news is that you can actually overcome this issue with some ease by installing a second electric or gas-powered heater. There are two main choices. You can connect various water heaters in parallel to increase the overall capacity and gallons per minute flow rate. Or, you can install a separate heater for a specific appliance, like your dishwasher or washing machine. That way, running that appliance won’t use any of the hot water you need for other uses.

Improved Safety

Compared to heaters with tanks or reservoirs, tankless ones tend to be safer. This comes from the fact that there is no tank from which they can leak. The lack of a tank also prevents potentially harmful bacteria, like Legionella, from hiding in it. The smaller unit and lack of tank also give you fewer parts that can be damaged in a natural disaster, such as an earthquake.

Improved Energy Efficiency

One of the biggest benefits of the best tankless water heater is the energy efficiency. If your home uses about 41 gallons of hot water every day or less, sticking to these on-demand heaters can increase efficiency by 24 to 34 percent. If you use about 86 gallons daily, then you still get increased efficiency, but not as much at 8 to 14 percent.

As a bonus, installing demand water heaters for each water outlet can increase those savings by 27 to 50 percent.

Some of the newer heater options take this a step further with smart connectivity and mobile apps. These can let you adjust them remotely to conserve energy.

Sensors Have Minimum Flow Requirements

Most tankless water heaters will only start working when they have a minimum amount of water flow rate. This can vary but is usually about 0.3 GPM. That means that if the water pressure is very bad, it won’t work.

If you have low water pressure, you can overcome this by choosing one of the (less common) tankless water heaters that don’t have these sensors.

Less Standby Heat Loss

Yet another advantage of an on-demand water heater is that you don’t have to worry as much about standby heat losses. This is sometimes a major concern with storage water heaters, as the heat in the water can dissipate as it sits there.

That being said, depending on the model you choose, you may have to pay attention to the pilot light. Some gas tankless water heaters lose a lot of energy through the pilot light, so this is worth checking before you buy. Of course, you could save gas by turning the pilot light off between uses.

Initial Price Tag vs. Longevity and Lifetime Value

Compared to a traditional storage water heater, you will have to pay a bit more for the appliance initially. However, they make up for that somewhat with the energy savings.

On top of that, electric or gas tankless water heaters typically last about 20 years. By contrast, storage ones only last 10 to 15 years, a lower rating.

Less Space

Because they don’t have a tank, an on-demand water heater will take up a lot less space in your home than one with a tank. This gives you more flexibility in terms of where to put it.

Easier Winterization

If you have a tankless heater on a property that you won’t use during the winter, you can easily drain the unit in seconds. By contrast, draining a heater with a tank would take a lot longer.

What to Consider When Looking for the Best Tankless Water Heater

We’ll go through our choices for the best tankless water heaters below. Before we do, however, take a few moments to understand the criteria that we use when selecting a tankless water heater to include on the list.

You can use these criteria to choose among our picks by weighing the importance of each factor to you. Or you can use them to find another water heater that appeals to you even more than one on our list, although we’re pretty confident that we picked the best ones.

Size, Flow Rate, and Temperature Rise

Generally speaking, the larger the tankless water heater is, the better its flow rate will be. In fact, most of the best tankless water heaters offer information on their flowrate as well as dimensions in the section of their description dedicated to sizing.

You can estimate how much GPM flow rate you need for your home. If you know the flow rate of various faucets and appliances that use hot water, you can calculate what you need. Just add all of the flow rates together to get your hot water needs.

The other aspect of sizing is the temperature rise. This is as simple as taking your desired water temperature and subtracting it from the current incoming water temperature. The typical requirement is a temperature rise of about 70 degrees Fahrenheit (bringing water from 50 degrees to 120). Depending on your dishwasher, you may need a greater temperature rise.

To give you an example of usage, most showers use a total of 2.6 gallons of water and are at about 104 to 106 degrees. So, assume you wanted to let two people take showers at the same time, and the water starts at 40 degrees Fahrenheit. You would need a temperature rise of 60 degrees and the ability to heat 5.2 gallons per minute.

The following are some other average figures for GPM flow rate and temperature needed for typical hot water uses to help you with your estimates:

  • Showers: 2.5 to 3 GPM, 104 degrees
  • Low-flow showers: 1.2 to 2 GPM, 104 degrees
  • Tubs: 4.0 GPM, 102 degrees
  • Kitchen sinks: 1.5 GPM, 110 degrees
  • Other faucets: 0.75 to 2.5 GPM, 110 degrees
  • Dishwasher: 1.5 GPM, 110 degrees
  • Washing machine: 2.0 GPM, 120 degrees

In addition to the flow rate written in GPM, you should also consider the BTU (British thermal units). A BTU (British thermal unit) is the amount of energy needed to increase a single pound of water’s temperature to a single degree Fahrenheit. This means that higher BTUs result in higher flow rates.

Because BTUs are standardized, most heaters will have similar BTUs depending on their GPM. Expect about 190,000 BTUs for 5.7 GPM or 31,000 BTUs for 1.2 GPM.


As you consider the flow rate that you need for your tankless water heater, consider your climate. The main consideration here is the temperature of the incoming water that enters your home. Remember that your heater will have to work harder to increase the temperature if it is colder outside. This can reduce your effective GPM rate.

In other words, if you live somewhere with very cold winters, you may want to opt for a tankless water heater with a higher GPM, so it can keep up with your demands even in the coldest months.

But if you live somewhere that is warm to temperate year-round, you can likely focus on other features and just make sure it has a fair flow rate.

Point-of-Use or Centrally Located

As mentioned earlier when discussing GPM and the flow rate of water heaters, you can install a unit that is designed to heat the whole house or just for a specific fixture or room. These are called centrally located or the whole house and point-of-use heaters, respectively.

While some tankless heaters can work in either situation, others are designed for one or the other. Think about how you plan to use your new tankless water heater and make sure the one you select is appropriate for that use.

Electric vs. Gas

Most tankless water heaters run on either gas (natural gas or propane) or electricity as their fuel type. Both are widely available in the United States. To choose, you will want to think about the costs of running the heater as well as your flow rate requirements. Remember that gas heaters tend to have higher flow rates than an electric tankless water heaters.

Depending on where you live and your home, you may also be able to get a water heater that runs on geothermal energy or solar energy.

As a refresher, the following are some pros and cons of gas tankless water heating units:

  • Quick response time for instant heat.
  • Higher flow rate than electric.
  • Unlimited hot water as long as you stay under the flow rate.
  • Use more gas than traditional heaters with reservoirs or tanks.
  • More expensive than electric ones.
  • Require regular inspections by professionals.
  • You may need to upgrade your gas supply lines.

The following are some pros and cons of electric ones:

  • Quick response time for instant heat.
  • More affordable than gas ones.
  • Simple design for easier maintenance.
  • You can typically complete maintenance yourself.
  • No exhaust gases and no required venting.
  • Lower flow rate than gas.
  • Sometimes require upgrades to the home’s electrical system.

Condensing Tankless Water Heaters

In addition to the general categories of gas and electric tankless water heater options, there are also condensing tankless heaters. These are a sub-type of gas or propane and include a heat exchanger ahead of the vent pipe. This exchanger takes the hot exhaust’s thermal energy, then uses it to preheat the water in the heater. The result is improved efficiency as the system has to use less new energy. It also makes the exhaust temperature cooler.

Despite the cooler temperatures, don’t use PVC pipes to vent the exhaust, even if the manufacturer claims it is fine. PVC is not rated for this type of application, so it may melt. Although it costs a bit more, always stick to metal venting.

Ignition Type on Gas Units

If you opt for a natural gas tankless water heater, you will have your choice of ignition types, with three main options. The ignition type for the gas models you choose can affect energy savings.

Standard ignition means there is a continuously burning pilot light. There is no need for an electrical connection, and the tankless water heater doesn’t have to detect water flowing to turn on. This method is convenient, but it does use more gas than other ignition types since the pilot is always on.

Power ignition doesn’t require an electrical connection or batteries. Instead, they automatically activate as soon as the water flows through the device, which includes a turbine.

Direct ignition requires you to connect the appliance to batteries or the electrical system. The system ignites when the water flows through it.

Venting Requirements

If you choose a gas tankless water heater, you may need venting. This will add to the installation costs and mean that this tankless unit takes up a bit more room since you need to find space to install the venting.

The good news is that if you install a gas heater outside, it doesn’t need venting. You will only need to install ventilation if it is indoors and gas-fueled.

There are two main types of venting methods, either power-vent or direct-vent. You may have a preference for one or the other of these. Power-vent units just need one ventilation pipe, which is used as an exhaust. Direct-vent tankless water heating units require an exhaust and an intake vent in most cases. However, some direct-vent systems have concentric vents that serve both functions.

The fact that direct-vent units get air from outside, you can install them even in cramped spaces. By contrast, power-vent ones use the air in the same room they are. This requires the room to be more spacious and have clean air.

Essentially, if you choose an indoor gas tankless unit, be prepared to pay extra for installation costs as they will need to set up venting.

If you currently have a traditional heater for your water, the tankless ones need unique venting, so you should still expect a cost in this respect. You can’t just reuse the previous system. The exception would be if you are replacing a propane tankless water heater with a new gas tankless one.

Indoor vs. Outdoor Units

Whether you choose a gas- or electric-powered unit, you will need to consider whether you want to put it inside or outside. Many tankless water heaters are designed for either indoor or outdoor use, although some can work in either location.

Outdoor units must be able to withstand the elements. They offer the benefits of not using up any interior space, and in the case of gas units, they don’t require venting. They also have simpler installation, which saves you money, and are cheaper to start. However, they are not ideal for areas with colder climates.

Indoor units are harder to install and will take up some room inside your home, but they are ideal if you live somewhere with harsh or very cold weather. Just remember that indoor gas units need ventilation.

Energy Efficiency

Whether you are looking at gas or electric heaters, you want to keep whether the unit is energy-efficient in mind. There are a few elements to this, which combine to create the energy factor (EF). The energy factor is an indication of how energy-efficient the heater is overall. It includes the recovery efficiency and cycling losses. For heaters with storage tanks, standby losses are also a factor, but they aren’t a concern with on-demand ones.

Recovering efficiency is the efficiency with which the heat moves from the energy source to the water. Cycling losses are the heat that is lost while the water circulates through the system of the heater.

More energy-efficient systems have higher energy factors. You can typically find the energy factor or efficiency rating in information from the manufacturer of a water heating unit, giving you a hint as to whether you should expect energy savings.

However, keep in mind that fuel costs can vary, so a system that is more energy-efficient doesn’t always translate into lower operating costs and energy savings.

You can also look for water heaters that have temperature controls, as these let you control the efficiency rating to some extent and reduce your energy bills.


Consider both the upfront cost of a potential best tankless water heater as well as the operating costs. Remember to consider the installation costs and future maintenance costs, as well.

To calculate the operating costs, you will have to check the energy factor and the fuel cost.

The following formula will let you calculate the estimated annual operating cost for a gas heater.

365 x 41045 / (EF x Fuel cost in British thermal unit) or 365 x 0.4105 / (EF x Fuel cost in therm)

The following formula lets you do a similar calculation for electric units, with the energy in kilowatt-hours (kWh). The 12.03 represents an average for kWh used per day.

           365 x 12.03 / (EF x Fuel cost)

When it comes to the installation cost of the tankless water heater, you will have to account for local building code requirements, climate, safety issues, and the fuel type. Most of these factors will not vary much based on the heater you choose, but the fuel type will, and safety issues may as well.


Another important aspect of the cost of your tankless water heater is the warranty. The best ones will feature an extended warranty, although the details will vary by brand and unit.

While a longer warranty is always better, it is particularly important if you have hard water in your home. This water will increase the wear and tear on the appliance.


There are several tankless water heater brands to choose from, whether you want a gas-powered unit or one that uses electricity. Some buyers may have a preference for their tankless heaters, and they are more commonly found in water heater reviews. However, you can rest assured that any of the tankless water heater brands listed below are reliable. Some examples include Rinnai, Takagi T H3 DV, H3 DV N, Rheem RTEX, other Rheem models, Stiebel Eltron Tempra, EcoSmart ECO, and the others mentioned below. Although no Rheem models made our list, the brand has a strong reputation, including the Rheem RTEX.

Legal Restrictions

Although most people will not have any issues with water heating units, some cities and counties have outlawed the installation of certain tankless water heaters. These bans typically only apply to a handful of models.

It means that you should always check for any local restrictions on tankless appliances in your area before you buy them. That is especially true if you opt for a model that is manufactured-to-order, as you won’t be able to return it.


Switching from your current water heater with a storage tank to a tankless version can save you money on your energy bills, as these units tend to be more energy-efficient than storage tank models. They also eliminate the need to wait for the water to heat up or the limited supply of hot water you get with a tank water heater. Instead, a tankless unit delivers instant or near-instant hot water that can last forever, as long as your use stays within the unit’s flow rate capacity. As a bonus, they also take up less space and last longer than units with a tank.

As you choose your tankless water heater, you want to consider the flow rate, temperature rise, ignition type, fuel type (electric or natural gas or propane), venting requirements, ideal location, efficiency rating, warranty, and price tag of the unit, as well as your climate and whether it will be for the whole house or point of use.

Any of the eight options we listed above would be a great addition to your home, thanks to their great flow rates, brand reliability, longevity, and other factors. Choose the best one for your needs based on your climate, typical water heating requirements for a supply of hot water, budget, and whether you prefer electric or gas-powered. Once you choose a unit, remember to have it installed by professionals.

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