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The only way to ensure that you never run out of hot water is to install an on-demand, or tankless, water heater. Tankless water heaters heat the water as you need it so there is no fear of running out.

Not only will a tankless water heater save you from ever having to suffer through a cold shower, but they are also better for your wallet and the environment. Tankless water heaters use less energy, are much less likely to ever leak, and they take up less space. Choosing the right water heater is vital, so we have done some research to provide you with the knowledge you need to choose the best tankless water heater for your home. Take a look at some of our picks for the best tankless water heaters, then we’ll discuss everything you need to know to make the right choice.

Top 5 Best Tankless Water Heaters of 2021

Reviews Of The Best Tankless Water Heaters

Stiebel Eltron Tempra Plus Electric Tankless Water Heater

Stiebel Eltron Tempra Plus Electric Tankless Water Heater

Quick Look: Electric, ventless design that comes in multiple sizes. Copper heating unit with advanced flow control. Comes with extended warranties. Check Price at Amazon

Stiebel Eltron is a big name in the tankless water heating scene, so it is no surprise that the Stiebel Eltron Tempra Plus Electric Tankless Water Heater would make our list. This electric model comes in multiple sizes, in terms of heating capacity, from a 1.2GPM up to 7.5GPM, so you are sure to find an option that meets your needs.

This unit uses advanced flow control to ensure that your water is consistently hot. Using a digital monitoring system, the unit registers if the hot water flow exceeds the heating capacity. If overuse is detected, the heater will slightly decrease the flow of water to ensure that all water is heated evenly. This means your hot shower will not be interrupted, even if someone downstairs turns on the dishwasher.

This water heater can be installed wherever it is most convenient for you and your hot water needs. It is compact, ventless, and completely noiseless, making it great for small spaces. Since it only activates when it is in use, it is energy efficient and even has an energy savings monitor on the display to show you how much you’ve saved by switching to tankless.

Learn More and Buy Now at Amazon
ECOTOUCH Electric Tankless Water Heater

ECOTOUCH Electric Tankless Water Heater

Quick Look: Electric, 1GPM heating capacity, no venting required. Energy-efficient, compact, and easy to install. Check Price at Amazon

One of the reasons that tankless water heaters are so much more efficient is that they can be installed closer to your fixtures. If you have a water heater installed under your kitchen sink you will never have to waste water waiting for the hot water to travel from your tank to the sink. With the compact ECOTOUCH Electric Tankless Water Heater, you can do just that. It is the perfect size to install under your kitchen or bathroom sink, giving you consistently hot water right when you need it.

This unit will heat water according to the water input. This means that it automatically adjusts the amount of heat according to the water pressure, eliminating the chance of over-heated water. By adjusting energy use according to water pressure, this unit also helps to save on energy costs.

The easy to read digital display makes setting the temperature a breeze and the included remote makes temperature changes even easier. This budget-friendly unit has a sleek design that can be mounted anywhere near your sink without looking out of place, even if you want to simply mount it on the wall. If you’re looking for a slightly bigger model that can heat water for more than one fixture, check out some of ECOTOUCH’s other models.

Learn More and Buy Now at Amazon
Camplux Propane Tankless Water Heater

Camplux Propane Tankless Water Heater

Quick Look: Compact, easy to install, and has ECO or full gas options. Designed for indoor installation. Color digital display for temperature control. Check Price at Amazon

When you live in a home or apartment with limited space, the last thing you want to do is give up a huge chunk of storage space for a bulky water tank. With this compact Camplux Propane Tankless Water Heater, you can have perfectly heated water on demand and keep all your storage space.

This water heater is perfect for a small home or apartment with a 2.64GPM heating capacity. It also has all the safety features you need to put your mind at ease. It comes with anti-freezing and overheating protection as well as dry combustion and flame-out protection.

Camplux designed this model to be as energy-efficient as possible, only burning fuel when it is in use. It also comes with ECO or full gas options, allowing you to save even more energy.

Learn More and Buy Now at Amazon
Rinnai V Series HE Tankless Water Heater

Rinnai V Series HE Tankless Water Heater

Quick Look: Natural gas or propane, outdoor installation only. Controlled via smartphone app. Easy to install and comes with an extended warranty. Check Price at Amazon

With 100 years of experience in building quality equipment, Rennai can be relied on to produce water heaters that you can trust. The Rinnai V Series HE Tankless Water Heater is perfect for both your home or small business. It comes in multiple sizes, meaning you can choose the heating capacity that best meets your needs. They also offer natural gas or propane models.

This high-efficiency water heater is designed for outdoor installation only, so it will not take up any storage space. If you live in a colder climate there is no need to worry about the outdoor installation. This model comes with an electric freeze protection heater so it can continue to function normally in temperatures as low as -30℉.

One of the most convenient features of this water heater is that it can be controlled by a smartphone app. You can change the temperature, set heating schedules, and even set it to vacation mode right from your phone without having to be near the unit. It is also WIFI compatible, so it can automatically notify your Rinnai service provider if maintenance is required.

Learn More and Buy Now at Amazon
Rinnai Sensei Super High Efficiency Water Heater

Rinnai Sensei Super High Efficiency Water Heater

Quick Look: Natural gas or propane, up to 11GPM heating capacity, designed for indoor installation. Uses Circ-Logic technology. WIFI compatible. Comes with extended warranties. Check Price at Amazon

If you want hot water on-demand for all the fixtures in your home using a single unit, then the Rinnai Sensei Super High Efficiency Water Heater is the unit for you. The Sensei is a high-efficiency tankless water heater that can heat up to 11GPM. This means you can run a load of laundry and wash the dishes while someone is in the shower and not worry about running out of hot water.

This super high-efficiency unit uses Rinnai’s patented Circ-Logic technology to help you save water and energy. This system uses a pump to recirculate the room temperature water in the pipes between the water heater and your fixtures which helps you save even more water energy.

The Sensei is available in a natural gas model as well as a propane model. It is designed to be installed indoors and requires ventilation, but since it is the size of a small suitcase, it won’t take up much of your space.

Learn More and Buy Now at Amazon

How We Chose The Best Tankless Water Heaters

There are several important details that you will have to look into to find the best tankless water heater for you, but in our search, we took a slightly broader approach to find something for everyone.

Energy Efficiency

One of the biggest selling points for tankless water heaters is that they are much more energy-efficient than traditional tank water heaters. With that in mind, we looked for units that took that energy efficiency to the max, no matter what their power source. Features like water flow activation, water recirculation, and flow control are all things that can make your water heater more energy-efficient and decrease your monthly energy bills.

Quality Materials

Another benefit of going tankless is that these units last a lot longer than traditional water heaters. Many tank models are meant to last 8 to 10 years where tankless water heaters can last up to twice that long. Not only that, but companies like Rinnai and Stiebel Eltron design their water heaters to have easily replaceable parts. This means that if something does malfunction, you can replace the part instead of having to replace the entire unit. Combine that with solid warranties and service options and you know you are investing in a quality piece of equipment.

Ease of Use

We looked for water heaters that were easy to understand and operate so that you can have complete control of how hot your water is with minimal effort. With these units, the temperature is easy to set or change and is always clearly displayed on the front.

We also looked for units that were easy to install. Although you should always have your water heater installed by professionals, there is no need to make it more complicated for them.

What You Need To Know About Tankless Water Heaters

Tankless water heaters are similar to their traditional counterparts in that you can purchase models to match the energy source in your home, but they use that energy differently. Since tankless water heaters heat the water as you need it instead of simply keeping a large quantity of water hot all the time, the specifications you need to pay attention to are a little different.

Gas Versus Electic

As we mentioned, tankless water heaters run on the same energy sources as traditional water heaters. If you have always had a natural gas water heater, you may be tempted to just default to buying a natural gas tankless unit, but there are a few things to consider first.


Gas models use either natural gas or propane to fuel a powerful flame that heats the water as it travels through a heat exchanger. This is a very straightforward process that works quite well, but there are some drawbacks. The downside is that all gas water heaters require airflow and venting to expel dangerous emissions. If you are replacing a traditional unit, the vents you have in place may not be sufficient because tankless units require more ventilation. This ventilation can also remove some of the heat from the unit, making it less energy efficient. Most of these units run at about 80% to 85% efficiency. These units also use a small amount of electricity to operate the thermostat and ignition.


Electric tankless water heaters use a similar process, but instead of a pilot light, they simply use electricity to heat the unit. Since these models do not require any ventilation or housing for the pilot light, they are often much smaller and can be installed in a wider variety of locations. Although electricity is often more expensive than natural gas, electric models are much more efficient, usually about 98% to 99% efficiency. They are also less expensive, both to purchase and to install, which may offset the slightly higher energy costs.

Max Temperature Rise and Flow Capacity

The two main factors that you have to consider when choosing your new tankless water heater are the max temperature rise and flow capacity. We’ll talk about how to determine your requirements in a minute, but first, let’s talk about what these terms mean.

Max temperature rise is the maximum temperature increase that any particular model can produce. For example, if a unit’s specifications say that it can produce a 70° temperature rise at 3GPM, that means it can increase the temperature of your water by 70° while it is flowing at three gallons per minute, approximately the equivalent of a high-pressure shower. How hot that shower will be all depends on the base temperature of your water.

The flow capacity is how many gallons of heated water the unit can produce per minute, which is directly tied to the base water temperature. If the water’s starting temperature is already high then the water heater can heat faster and produce more water. If the base temperature is low, it will take longer to heat, decrease the flow capacity.

How to Choose The Best Tankless Water Heater For Your Home

Now that we know about max temperature rise and flow capacity, let’s discuss how you can determine which options are the best for you.

Determine Your Base Temperature

Most people will not know the temperature of their groundwater and that is okay. There is no need to bust out a thermometer or anything like that because most tankless water heater manufacturers already have that information based on where you live. They have handy maps that indicate temperature approximations for the entire United States. The temperature ranges from approximately 35° to 77°, which is quite a wide range. You can easily see why it is so important to know what the groundwater temperature is in your area so you can be sure to purchase a unit that is powerful enough to get the job done.

Determine Your Flow Requirements

Once you know how much of a temperature rise you need, you need to determine your flow capacity. The best way to figure out what will work for you is to consider the number of fixtures you have and how often you will be using those fixtures simultaneously. Here is a general idea of the amount of water used by the most common fixtures in your home:

  • Bathtub: 4GPM
  • Shower: 2-3GPM
  • Washing Machine: 2GPM
  • Dishwasher: 1.5GPM
  • Kitchen and Bathroom Sinks: 1-1.5GPM

Based on these approximations you can determine the amount of hot water you are going to use at any given time. For example, if you have two showers and you want to be able to wash laundry while those showers are in use, you would need a minimum of 8GPM flow capacity, but you should aim for higher, possibly 10 to 12GPM. Since running out of hot water is exactly the situation we want to avoid, be sure to choose a flow capacity that reflects the maximum amount you expect to be using.

Thankfully, there are a few options available to ensure that you never run out of hot water. The first option is to buy a large high capacity unit. If you want to use natural gas or propane, this is probably the best choice for you. Gas units are more expensive, both initially and in installation costs, so choosing a single large unit is best. If you are looking at electric units, you may find it beneficial to install multiple units, such as one for the bathrooms and one for the kitchen.

Keep in mind that not everyone needs to have two showers and the washing machine going at the same time. More often than not, a flow capacity of 5 to 6GPM is sufficient for a small family home. If you live alone or with one other person, you may not even need that, just remember not to sell yourself short by buying a unit that is too small to meet your needs.

Understand the Installation Process

Remember, your water heater is an extremely important part of your home, but it can also be very dangerous if it isn’t installed correctly. Always enlist the help of professionals when you are installing anything that requires gas or electricity. Also note that if you are building a new home or doing a large remodel, your home may have to undergo a safety inspection and that includes your water heater. Be sure to check the regulations in your area to ensure that you choose a unit that meets all the safety requirements.

Bottom Line

Endless hot water is like a dream and it is a dream that can come true with the right tankless water heater. Switching to a tankless water heater can help you on your way to a more energy-efficient home as well as save you money and hassle. Tankless units take up less space, are easier to fix, and they are built to last longer than traditional water heaters.

It’s hard to go wrong with any of our top tankless water heater options, but we recommend Stiebel Eltron Tempra Tankless Water Heater for its energy efficiency and quality materials. Compare all of your options before making a final decision, though, to make sure that you’re choosing the right model for your circumstances.

Top 5 Best Tankless Water Heaters of 2021