The Best Tankless Water Heater Reviews

Switching from a traditional hot water tank to a tankless water heater is one of the best ways to save money every month on your utility bill. According to, tankless heaters can offer up to 37% energy savings. That’s why we put together the best tankless water heater reviews to make your purchase decision easy.

Millions of people are the world are making the switch to tankless hot water heaters for more than just saving money, they are saving the environment too.

Don't Feel Like Reading? Here's our #1 Pick for The Best Tankless Water Heater

Rinnai RUR98iN 9.8 Max GPM Ultra Series

The Best Gas Tankless Water Heater

If you want the most powerful, efficient and technologically advanced natural gas tankless water heater in the market, then look no further than the Rinnai RUR98iN Ultra Series. This whole house tankless water heater can meet nearly any demand with a 96% energy efficiency factor in addition to advanced features such as WiFi controls and water recirculation.

Why Go Tankless?

Tankless water heaters provide instant, on-demand hot water. Hot water tanks keep a fixed amount of water hot at all times.

This is an important distinction. The hot water tank uses energy all day long (gas or electric) whereas the tankless heater only draws power when hot water is demanded.

Gas vs Electric Tankless Water Heaters

The first choice you’ll need to make is what power source you need to heat your water. The main power sources are natural gas (propane can be used as well) or electricity. If your home doesn’t have a gas line, the choice is easy. If both options are available, here are the pros and cons of each:

Gas Powered Tankless Water Heaters

Whether it is natural gas or propane, these pros and cons will apply to the unit.


  • Much more powerful, able to heat multiple faucets at once
  • Lower cost than electricity in most cases
  • Able to heat water from cold incoming water temperatures


  • More expensive than electric heaters
  • Emit emissions directly from the unit
  • May require ventilation, depending on the unit and placement

Electric Tankless Water Heaters

Electric tankless water heaters are smaller and more affordable than gas powered heaters.


  • Doesn’t directly emit CO2 (your electricity may come from a coal plant, however)
  • More affordable than a gas powered heater
  • Doesn’t require any ventilation


  • Most homes would require multiple units to produce the same amount of hot water as a gas powered unit
  • Require more maintenance due to limescale and calcium build-up
  • Electricity is generally more expensive than gas

Buying a single, large, gas powered tankless water heater or buying multiple electric tankless water heaters can produce the same hot water output for roughly the same initial cost.


Best Tankless Water Heaters Comparison Table

NameFlow RatePower TypePrice
Rinnai RUR98iN 9.8 Max GPM Ultra Series9.8 GPMNatural GasView Price
Rinnai RUC98iN Ultra Series9.8 GPMNatural GasView Price
Stiebel Eltron Tempra Plus4.0 GPMElectricView Price
EcoSmart ECO 273.0 GPMElectricView Price
Rheem RTGH-95XLN Prestige9.5 GPMNatural GasView Price
Rheem RTG-84XLN Low NOx8.4 GPMNatural GasView Price
Takagi T-KJr20-IN-NG6.6 GPMNatural GasView Price
Bosch Electric Tankless Water Heater1.0 GPMElectricView Price
SioGreen IR260 Infrared2.0 GPMElectricView Price
Eccotemp L10 Portable Outdoor2.0 GPMPropaneView Price

Tankless Water Heater Reviews by Category

1. Best Gas Tankless Water Heater:  Rinnai RUR98iN 9.8 Max GPM Ultra Series

The Best Gas Tankless Water Heater

Click to view Price

If you are looking for nothing but the best of the best in tankless water heating for your whole house, look no further than the Rinnai RUR98iN, considered by many to be the very best tankless water heater every produced for residential use. With an impressive 96% efficiency factor, the ability to provide 9.8 GPM of hot water flow at nearly any incoming water temperature, this tankless water heater by Rinnai is capable of replacing your traditional hot water heater in nearly any climate.

Some of the features we love and are unique to this unit are it’s Wifi Capabilities, so you can monitor and change your water heating settings over your home network and the innovative re-circulation line which allows this unit to produce an endless supply of hot water. Very few tankless water heaters offer these features; and while they may be luxurious, the investment in this water heater will easily pay for itself in both energy savings and ease of use.

The Pros

  • Can meet any residential house’s need
  • Produced by an industry leader in water heaters
  • Hassle Free Warranty Process
  • No Expansion Kit Required
  • Very Silent
  • Dual Pipe makes unit more efficient by using condensation water

The Cons

  • Most expensive unit you will find for residential use
  • Requires venting and does not come with a venting kit
  • Might be excessively powerful for smaller homes

2. Runner Up Gas Tankless Water Heater: Rinnai RUC98iN

Best Whole House Tankless Water Heater

Click To View Price

We can say with confidence that if you’re looking for a tankless water heater to provide on-demand hot water for your whole house, then the Rinnai RUC98iN Ultra Series is the unit for you. With the ability to produce a staggering 9.8 GPM of hot water with a temperature rise of 50F, this natural gas powered water heater is perfect for nearly every home in the United States. Many tankless water heaters, especially electric, aren’t capable of providing hot water for an entire house, and many natural gas powered ones don’t have the same GPM flow rates as the Rinnai RUC98iN.

It’s important to note, as with any tankless water heater, that it may take up to 20 seconds for the water to heat up from the heating unit to the faucet; but once it’s warmed up, you have an unlimited amount of hot water while enjoying cost savings from the energy efficiency.

We recommend professional installation since this unit requires a natural gas hook up.

The Pros

  • Can meet nearly any capacity need
  • Produced by an industry leader in water heaters
  • Hassle Free Warranty Process
  • No Expansion Kit Required
  • Very Silent
  • Dual Pipe makes unit more efficient by using condensation water

The Cons

  • Most expensive unit you will find for residential use
  • Requires venting and does not come with a venting kit
  • Might be excessively powerful for smaller homes

3. Best Electric Tankless Water Heater: Stiebel Eltron Tempra Plus

The Best Electric Tankless Water Heater

Click to View Price

Electric Tankless Water Heaters have been making strides in recent years, and one of the leading companies in this industry is Stiebel Eltron, with their flagship product the Tempra Plus. With their largest units being able to provide an impressive 4.0 GPM with incoming water temperatures of 72F, this is truly one of the most powerful and efficenent electric tankless water heaters available in the market today.

The features we love about this water heater are definitely the easy to use digital controls, the small and sleek design that allows you to install it nearly anywhere, from under the sink to behind a furnace or in a small utility closet. It is also highly efficient and can nearly match the energy cost of a natural gas water heater, or outperform it significantly using solar as a power source.


  • Best in class flow rates for electric tankless
  • Trusted by many verified online purchases and reviews
  • Great warranty for peace of mind
  • Industry leader


  • Slightly more expensive than other models
  • Will require 2+ units to provide for an entire house


4. Runner Up Electric Tankless Water Heater: EcoSmart ECO

Best Electric Tankless Water Heater

Click to View Price

If you have a simple need to place a water heater under your sink, perhaps for a cabin or a new powder room added to your home, then the EcoSMART ECO electric tankless water heater is the right unit for you. With the ability to provide 1.5 GPM flow rate with a 50F temperature rise, this unit would be perfect even if your incoming water temperatures are quite cold. Generally, electric tankless isn’t capable of handling high GPM flow rates, but for a simple sink, this unit will be more than enough for nearly any home of any incoming water temperature.

EcoSmart is a highly trusted brand in electric tankless water heaters, and for good reason. They have one of the most efficient units on the market and is a best seller 3 years in a row on major online retailers, while consistently maintaining a very high positive review score.


  • Great value – flow rate and quality for the price
  • Trusted by many verified online purchases and reviews
  • Great warranty for peace of mind


  • Somewhat unknown brand
  • larger unit than expected
  • louder than the competition

5. Best Outdoor Tankless Water Heater: Rheem RTGH-95XLN

Best Outdoor Tankless Water Heater

Click to View Price

A very high quality and highly rated outdoor tankless water heater, the Rheem RTGH-95XLN Prestige is one of the best water heaters you can find in the market, for the outdoor category. With one of the highest energy factors in the market (94%) and one of the highest flow rates (9.5 GPM), this can meet the needs of the majority of American homes, and requires no ventilation!


  • One of the best brands in water heaters, Rheem
  • Standard 10 year warranty
  • Leading energy efficiency rate at 94% (Compared to other outdoor units)
  • Very high flow rate at 9.5 GPM
  • Does not require any ventilation, since it is outdoor.


  • While it seems expensive up-front, the high energy efficiency will make it cheaper over time.

6. Runner Up Outdoor Tankless Water Heater: Rheem RTG-84XLN

Runner Up Best Outdoor Tankless Water Heater

Click to View Price

If you’ve decided on going with an outdoor tankless water heater and want to save a few dollars from the high end models — then the Rheem RTG-84XLN is the right choice for you. With a strong flow rate of 8.4 GPM, which is satisfactory for the majority of American households, strong efficiency and low emissions, this “middle of the road” outdoor tankless water heater is the right choice for many homes.

Some of the features we love about this water heater are the remote control, which is great in the winter so you don’t have to go outside to adjust your settings. We also like the environmentally conscious design not only with energy efficiency but also the low emissions. Compared with a hot water tank run on natural gas, you will not only save a ton of money but save tons of carbon from the atmosphere.


  • One of the best brands in water heaters, Rheem
  • Standard 10 year warranty
  • Leading energy efficiency rate at 84% (Compared to other outdoor units)
  • Strong flow rate at 8.6 GPM
  • Does not require any ventilation, since it is outdoor.


  • May not last as long in harsher climates

7. Best Value Tankless Water Heater: Takagi T-KJr2-IN-NG

Best Value Tankless Water Heater

Click to View Price

If you are looking for that “middle of the road” tankless water heater, that is both of high quality and reasonable demand, then look no further than the Takagi T-KJr2-IN-NG Natural Gas Tankless water heater. Takagi is a well known name in the industry (although not as reputable as Rheem and Rinnai), and they come very highly rated on various online shopping websites. With the ability to generate a maximum of 6.6 GPM for under $500.00, this is the absolute best value in GPM on the market today.


  • One of the most powerful tankless heaters below $500 price mark
  • Built by a reputable brand name
  • Comes with a standard 10 year warranty
  • Very easy to maintain, comes apart easily


  • One of the louder units you can find
  • 6.6 GPM won’t meet the needs of a medium sized house
  • Only 81% energy efficient, so in some respects it’s more expensive than the high efficiency counterparts.

8. Best Under-Sink Tankless Water Heater: Bosch Electric Tankless

Best Under-Sink Tankless Electric Water Heater

Click to View Price

If you want a simple, affordable and easy to install tankless water heater for under a kitchen or bathroom sink, the Bosch Electric Tankless Water Heater is surely the unit for you. While not suitable for larger uses such as a dishwasher or shower, this simple unit can provide unlimited hot water to your sink for under $200, one of the only units in the market capable of achieving this.

In addition, this unit is highly efficient, at 98%, meaning you require very little electricity to actually run this unit. With power ranging from 3.2 KW to 12kW, you can adjust based on your needs and incoming water temperatures, without breaking the bank with your monthly utility bills. We also love the fact that the unit itself is sleek, small and well designed, making it able to fit under your sink without sacrificing needed storage space.


  • One of the smallest units
  • Well reviewed by thousands of users
  • Industry leading warranty
  • Quiet unit for electric tankless


  • Low flow rate, only useful for single sinks


9. Best Recreational Vehicle (RV) Water Heater: SioGreen IR260

Best RV Tankless Water Heater

Click to View Price

Since an RV is likely to be subjected to a variety of different water sources, we recommend using the SioGreen IR260 Infrared Electric Tankless water heater for your recreational vehicle. This innovative water heater uses materials that resist the build up of calcium and limescale, which requires minimal maintenance. With the ability to produce up to 2.0 GPM, you could even provide hot water for a shower with this small unit.

One of the biggest draw backs to electric tankless water heaters it the build up of limescale and calcium, especially when the water source is hard. When you are traveling in your RV, you will encounter hard water, even if you usually have a soft water source. That is why it’s imperative to use an infrared water heater instead of a traditional electric tankless unit.


  • Maintenance free water heater
  • Well reviewed by thousands of users
  • Industry leading warranty
  • Quiet unit for electric tankless


  • Low flow rate, doesn’t work well for high flow showers
  • Larger than expected

10. Best Propane Water Weater: Eccotemp L10

Best Outdoor Shower Water Heater

Click to View Price

If you plan to spend an extended period of time in the outdoors, be it at your cabin, camping or otherwise, there is nothing better than a hot shower at the end of the day. The Eccotemp L10 Portable Outdoor Tankless Water heater is one of the best you can find to suit that need. Powered by propane, this water heater is able to heat nearly any incoming water temperature and provide refreshing hot water to your ourdoor shower.

This unit works with the standard 20lb propane tank and comes with the standard garden hose adapter. Simply buy it, hook up your gas line and garden hose, and you are off to the races! This unit is even capable of handling temperatures below freezing!


  • Powerful unit capable of handling any incoming water temperature
  • Backed by one of the biggest names in water heaters
  • Industry leading warranty
  • Works with standard garden hose and BBQ propane tanks


  • Water can take a while to heat up
  • Uses more propane than you would expect
  • We recommend an external cover to keep it protected, not included

What size tankless water heater do I need?

For the purposes of this chart, we will assume that incoming water temperatures are 67F or above. If not, you will generally want to play it safe and buy our top pick for the best whole house tankless water heater.

Demand TypeSize
Bathroom Sink0.5 GPM
Standard Shower2.5 GPM
Low-Flow Shower1.5 GPM
Dishwasher1.0 GPM
Washing Machine1.5 GPM
Kitchen Sink0.5 GPM
Laundry Sink1.0 GPM
Apartment / Condo13.0 GPM
Small House (<1000 sq. ft.)14.0 GPM
Average House (<1600 sq. ft)27.5 GPM
Large House (1600+ sq. ft)3+10+ GPM
1 bedroom 1 bathroom apartment with appliances
A normal apartment with a bathroom sink, shower, kitchen sink and dishwasher (but no washing machine), you would need a 4.0 GPM flow rate to run everything simultaneously. One option would be to buy two electric water heaters, one for the bathroom and one for the kitchen.
2 bedroom 2 bathroom
A 2 bedroom 2 bathroom house will generally have 2 showers, 2 bathroom sinks, a kitchen sink and dishwasher as well as a washing machine. In order to run everything at once, you will need at least 8.5 GPM. Of course, you won’t need to run everything at once, so you might be able to get away with 7.5 GPM. However, bear in mind you need more power in the winter for the higher temperature rise requirement.
4 bedroom 3 bathroom, in-law suite
In a large home with 3 showers and bathroom sinks, 2 kitchens with 2 dishwashers and 2 washing machines would require over 15 GPM of flow rate to provide hot water to all faucets at the same time. While this is an unlikely scenario, it is a good idea to have at least two gas powered tankless water heaters to provice sufficient demand to the entire house.

Indoor vs Outdoor Tankless Water Heater

While in general, we recommend buying indoor tankless water heaters, you have to consider two important factors before ruling out an outdoor heater.


In some instances, space may be a serious constraint and you can save space by placing the water heater outdoors. For example, in a small cabin or cottage, or a multi-unit building that requires multiple units can save a lot of indoor square footage, proportionally speaking.


Some water heaters make more noise than others, although all of them make some noise. In a small enclosed space, this can be irritating, and can be avoided by placing the unit outside.


If ventilation will be overly complicated or constrained for some other reason, you may want to place the unit outside to avoid all ventilation concerns. Ventilation tends to also take up more space than is available.

Incoming Water: Hardness and Temperature


If your incoming water temperature is below 50F, you will have to get a gas powered tankless water heater. Electric heaters are simply not powerful enough to raise the temperature more than 30F at best. Unless you are willing to give up hot water during the winter, you’re likely better off going with a gas powered unit. If you have a cottage or cabin that is only used in the summer, then electric might be a great choice.

In general, using an electric tankless water heater all-year round in a home is only available in the southern United States.


If your water is particularly hard (ie, you need to use a water softener), then you will require to do more maintenance on your tankless water heater, or use additional equipment to soften the water before it enters the hot water heater. Limescale and calcium build up can destroy your unit if it’s not cleaned regularly.

How do Tankless Water Heaters work?

All tankless water heaters work more or less the same way: incoming water enters a heating chamber and energy from the power source for the heat exchanger. Energy is transfered from the heat exchanger to the chamber and water is then drawn to the outgoing pipe where the demand is coming from. [source]

Different tankless heaters use different materials and are used for different purposes. That’s why it’s important to do your research to ensure you get the right tankless hot water heater for your exact needs.

In our guide, we will try to simplify all the important factors that would impact your buying decision.

Tankless Water Heater Cleaning and Maintenance

If you are already a handy person and familiar with water heater maintenance, check out these quick refresher videos on how to flush your water heater.

It’s also important to clean out the filter, which can accumulate some sediment as well. This video quickly explains how to do it.

If you are a beginner and have never performed maintenance before, are you are nervous about performing your up-coming routine maintenance on your tankless water heater, this 8 minute video takes you through the process — step by step.

It’s important that you don’t use store-bought descaling products, as they contain harmful chemicals that can run off in your tap water. As mentioned in the video below, use all natural, pure white vinegar. It’s completely safe for humans to consume, no need to worry if you don’t flush 100% of the vinegar out of the system.


Tankless water heaters are not a new technology and tens of thousands of households are benefiting from their wise decision to save money every month. Preserving the environment by using less energy (thus, less coal to be burned in power plants) while saving money is a win-win situation. Most homes that use traditional hot water tanks are also renting them from utility companies, costing them even more in rental costs. If you switch from a hot water tank rental to a tankless hot water heater you can reduce your monthly utility bill by up to 50%!

The draw back of course is that you have to do routine maintenance on your water heater, but hopefully this guide shows that it pretty easy and straight forward, and doesn’t involve any danger.

We hope that our tankless water heater reviews helped you choose the perfect water heater for your home, cabin, cottage, RV or a simply to put under your sink.

Image credit:

  • Rating