Best Whole House Tankless Water Heaters – 2021 Complete Buyer’s Guide

| Last Updated: September 22, 2021

Instant hot water is a luxury, and the best way to get it is with the help of a tankless water heater

These whole-house tankless water heaters heat your water quickly. You can use them without facing any difficulty. They are compact and aesthetically appealing as well, making them a great addition to your house.

To help you pick the best unit possible, we’ve listed and reviewed some of the best models available on the market.

Comparison Chart of the Best Whole House Tankless Water Heaters

IMAGEPRODUCT
  • Saves space, money, and energy
  • Contains a digital heat control mechanism
  • Latest self-modulating technology that will adjust the input energy according to the requirement of hot water
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  • Has side NPT water connections of 1/2 inch
  • Includes a digital thermostat along with an LED
  • Unit is 99.8% energy efficient, making it a great investment
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  • Best for the money
  • 97% efficient and very easy to install and use
  • External knob for controlling and stabilizing the temperature
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  • Best whole house electric tankless water heater
  • Reliable and provides enough hot water for the whole house
  • Can work on 208 Volts or 240 Volts and has a very sleek structure and design
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  • Best whole house gas tankless water heater
  • Operates using gas at 3.6 GPM and has a safe electronic system for ignition
  • Contains water fittings of ½” NPT and a very easy-to-understand instruction manual
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How Do I Choose a Tankless Water Heater?

Buying the perfect tankless water heater for your home that fulfills everyone’s hot water needs is a difficult task. It is not a piece of cake. You need to think about a lot of factors before buying one. Some of them are:

Usage of Hot Water

The first thing you need to consider is the amount of hot water you will need in your homes, business, or office. These heaters have no storage tank, so you need to be careful about running out of hot water. Different things like tubs, sinks, showers, and washing machines have different gallons per minute at different temperatures. The GPM factor depends upon your usage and the temperature value.

EcoSmart ECO 27

Mode of Supply

The second thing you need to be careful about is the source of energy that you’ll provide to the heater. These heaters use electricity or gas. If your area has a shortage of gas, then you must select a heater that has an electric element and vice versa.

Distance Between the Unit and Water Source

The distance at which you will place the tankless heater is really important. Some heaters do not work properly when they are located at a far distance from their water source. So, you need to consider the distance from the water source to the place where you will fit the unit.

Review of the Best Whole House Tankless Water Heaters

If you are searching for a tankless water heater for your whole house, then the heaters reviewed below deserve your attention. These are the very best of their kind available on the market. They will help provide hot water throughout your whole house. 

Best Overall

EcoSmart ECO 27

EcoSmart ECO 27 Electric Tankless Water Heater, 27 KW at 240 Volts, 112.5 Amps with Patented Self Modulating Technology,White

Specifications

Max Water Flow (GPM): 6.5

Energy Factor (EF): N/A

Dimensions: 3.63 x 17 x 17 inches

Water Temp Range: N/A

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What Recent Buyers Report

According to recent buyers, this tankless heater can heat up quite a lot of water. It is a great product for your homes. It is a smart device, which will help you with heating water anytime. It does not create any mess during the installation process. It is also an energy-efficient unit that can help you save on electricity costs.

Why it Stands Out to Us

The features of the EcoSmart ECO 27 are quite impressive. It provides endless warm water for a hot bath. You can replace the elements of this heater without any difficulty. It has a compact structure; thus, it will consume very little space. You can also set the temperature according to your requirements.

Who Will Use This Most

This heater is very useful for people who don’t have any gas access in their homes. You can use it in chilly areas as well for taking warm and hot baths. People can also use it for washing purposes. You don’t need to wash the dishes using cold water anymore!

Bottom Line

In a nutshell, this heater will use very little energy and space. It will also save money because of how energy-efficient it is. You can operate it without facing any issues. This heater is one of the most famous electronic heaters on the market. It heats the water passing through the line rather than storing it, so you can use it for a whole day without any stress.

Pros

Contains a digital display for temperature control

Replacement of elements in the heater is very easy

Very compact size and design, which allows you to save space

Switches on only when you want to heat the water, thus saving energy

Does not store water; instead, it heats the water passing through the unit, providing endless warm water

Cons

Elements of the heater corrode easily

One user claims that at times, the lights of the house flicker while using this heater

Runner-up

Rheem 240V RTEX-13

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

Specifications

Max Water Flow (GPM): 3.17

Energy Factor (EF): N/A

Dimensions: 12.63 x 8.25 x 3.63 inches

Water Temp Range: N/A

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What Recent Buyers Report

Purchasers have mentioned in their reviews that this heater will help you take a relaxing and comfortable hot shower. It provides enough water at a time for a single bathroom. It has a perfect digital temperature setting and LED display. Users also like that they can set the temperature according to their needs, giving them more control over their hot water supply.

Why it Stands Out to Us

This tankless heater holds the runner-up position on our list because of its amazing features and specifications. You do not require any extra overflow line for this heater. It also prevents water from being wasted due to the showerhead facility. You can install and use it without any difficulty.

Who Will Use This Most

The Rheem 240V RTEX-13 can heat the water of your home for a continuous 24 hours. It is energy efficient and will save your water too. You can use this heater in cold areas for washing, bathing, and laundry. People can also use it to wash their pets, such as cats and dogs. Overall, it can be used for all applications where hot water is needed.

Bottom Line

You can buy and use this heater without any doubt or confusion because it won’t waste your water and energy and you can easily use it to heat your water 24/7. This tankless heater contains an LED, which will help you in setting the thermostat according to your needs. Thus, you can greatly benefit from it.

Pros

Does not require any overflow line

Very easy to install and replace faulty components

You can set the temperature of the heater according to your needs

Self-modulating power can also be set depending upon the requirements

Includes a showerhead, which is a water saver, thus ensuring less wastage of water

Cons

Packaging is very poor

Lifespan is reported to be short

Can heat water up to 60 degrees only

Best for the Money

Bosch Electric Tankless

Bosch Thermotechnology - WH27 Tronic 6000 C Electric Tankless Water Heater - Eliminate Time for Hot Water - Easy Installation 26.9 kW

Specifications

Max Water Flow (GPM): N/A

Energy Factor (EF): N/A

Dimensions: 15.5 x 4.5 x 12.5 inches

Water Temp Range: N/A

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What Recent Buyers Report

According to some reviews, this electric tankless heater is worth buying because it offers good performance for an unbelievable price. Users report using it for a number of applications, such as for hot water supply in their kitchens and washrooms. They also report using it without any difficulty, and they found the installation to be a breeze. This is a great way to replace the gas water heaters in your homes. It provides endless hot water very quickly.

Why it Stands Out to Us

This Bosch Electric Tankless heater is the best replacement for you. You don’t need to heat water using a pan, boiler, and gas heater. Its quality is worth praising and lasts for more than 20 years. It prevents corrosion and wastage of water.

Who Will Use This Most

You can use this electronic heater for professional and home purposes. People can also use it to take steam baths. Customers who can’t use gas heaters due to a shortage of gas can also use this electronic heater. Industries that require hot water for their products can also make use of it because it can supply a sufficient amount of hot water.

Bottom Line

In sum, this is a high-quality heater available at an affordable price. Every single penny you will spend on it is worth it. It is very simple to operate and has a built-in sensor that will check and balance the water flow. You can use it for multiple purposes, both personal and commercial.

Pros

Life expectancy for this heater is 20 years

Built-in sensor for checking and maintaining the water flow

You can easily control the temperature using the external knob

Consumes very little space but promises a healthy quantity of hot water

Portable 26.9kW heater; thus, you can carry it anywhere without any difficulty

Cons

Reset button is very hard to push

Heats intermittently and trips the breaker

One user reported problems after a few months of usage

Best Whole House Electric Tankless Water Heater

Stiebel Eltron Tempra 24 Plus

Stiebel Eltron Tankless Water Heater – Tempra 24 Plus – Electric, On Demand Hot Water, Eco, White, 20.2

Specifications

Max Water Flow (GPM): N/A

Energy Factor (EF): N/A

Dimensions: 4.63 x 16.63 x 14.5 inches

Water Temp Range: 86 – 140 degrees F

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What Recent Buyers Report

Customers have praised this as an excellent water heater. The electric bill does not increase its usage. The quality of this heater is much better than the previous version. While some customers are not happy with the continuous tripping of the breaker, other reviews claim that it is a great product with exceptionally supportive customer service.

Why it Stands Out to Us

The Stiebel Eltron 224199 has a very sleek build, which makes it possible for you to install the heater at any place. You won’t need any ventilation for it. It provides maximum hot water for the whole house. It will also not cause a burden on your pockets afterward. In addition, this unit comes with a 7-year warranty on leakage and a 3-year warranty on defective parts, so you don’t need to worry about the repair cost at all.

Who Will Use This Most

This heater is an ideal choice for residential and industrial uses. In homes, you can use it to take steam baths. You can even use it to shower your pets during winter seasons. In addition, this heater is very helpful for the chemical, soap, and detergent industries. It can heat water within a few minutes.

Bottom Line

This heater is known for its rapid and excellent performance, which can provide you with hot water instantly. You can use it in different places. You don’t need to fret about finding the perfect location for fitting this heater because of its sleek design. It does not require any ventilation or outlets to pass out the steam, adding to its convenience.

Pros

Does not require any venting for the gas

Digital thermostat for temperature control

Compact and sleek; thus, you can fit it anywhere

Saves almost 15% to 20% of the hot water billing portion from your electricity bill

Provides a 7-year warranty for leakage and a 3-year warranty for the parts of the heater

Cons

Can trip the circuit breaker present on the tank

Heating capability decreases after a few years

Clogs the faucets as the calcium particles break from the tank

Best Whole House Gas Tankless Water Heater

Eccotemp FVI12-LP

Eccotemp FVI12-LP Liquid Propane Gas Tankless Water Heaters, White

Specifications

Max Water Flow (GPM): 3.6

Energy Factor (EF): N/A

Dimensions: 24.75 x 15.25 x 6 inches

Water Temp Range: 80 – 140 degrees F

$309.00 On Amazon

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What Recent Buyers Report

Recent buyers have written in their reviews that this is an excellent heater. It is an inexpensive tank that provides hot water within a few seconds. People love to use it for heating the water in their homes because of its fast speed and great quality. Overall, users have no complaints regarding its functionality.

Why it Stands Out to Us

This heater will never cause you disappointment. It includes an instruction manual, propane tank, wall thimble, hardware pack, and a termination pipe. It has a stainless vent pipe, thus, no corrosion. It will save both energy and money. It only works during the time you will use hot water, so you must try this heater once.

Who Will Use This Most

You can use the Eccotemp FVI12-LP for small residential areas, cabins, homes, and apartments. It produces very little noise. You can fit it anywhere in your home to heat the water. It will also save energy.

Bottom Line

To conclude, this gas heater is perfect for home uses. You can use it to heat water for urgent uses. Its quality and performance are worth praising. You can operate it without any tension. Plus, the instruction manual will provide you with enough guidelines, making this unit great for beginners too.

Pros

Beautiful design and a metal door

Vent kit is made up of stainless steel

Digital display and a manual temperature control

Produces very little noise and consumes little space

Operates only when someone is using hot water, thus saving energy and power

Cons

Can only supply hot water for one bathroom

Adjusting the temperature is a little bit tricky

Although it is a gas heater, it requires electricity for the exhaust fan

What Size of Water Heater Do I Need to Support My Whole House?

You should select the right size of the heater for your home. A very small heater will not be sufficient to provide enough hot water for fulfilling everyone’s needs. Similarly, a large heater will consume more space and energy. 

The number of gallons you ideally need for your family depends upon the number of people in your family. If you have 1-2 family members living in your home, then 30 to 40 gallons will be enough. Similarly, for 2-3 people, a heater of 40-50 gallons is perfect. 3-4 people can use a 50-60 gallon heater, and a family of more than 5 can use 60-80 gallons. The size of the heater is dependent upon the number of occupants.

What Are The Advantages and Disadvantages of a Tankless Water Heat?

The concept of tankless heaters might seem interesting to you. But you should be aware of their pros and cons. You need to know everything about a product before purchasing it.

Advantages

There are a lot of advantages to using a tankless heater. They are a replacement to many of the manual heaters. They contain the latest technology and features. Let’s have a look at some of their advantages.

Saves Energy, Space and Time

Using tankless heaters, you can save time, considering that they can heat water within a few minutes or seconds. You just need to set the temperature, and it will provide you hot water according to your requirements. They are very small and compact; thus, they consume very little space. You can also avoid energy wastage with them, as they only operate when you need hot water. 

Less Wastage of Water

These heaters do not store water; instead, they use the water going through the pipeline for heating. They do not require any extra overflow pipeline. Tankless heaters do not heat the water continuously; they only start heating when you will need hot water.

Bosch Electric Tankless

Warranty and Lifespan

Tankless heaters have a longer life expectancy than storage heaters. They do not corrode or wear off easily. They have a longer warranty period. You can use them without any tension.

Disadvantages

Tankless heaters also have some disadvantages. The most prominent one is:

Hot Water Supply

These heaters do not provide enough hot water, meaning that you can’t use it for hours on end. It can’t continuously heat up water and provide hot water throughout the day; you can only use it intermittently. 

Conclusion

As you can see, tankless heaters have far more advantages than disadvantages. You can use them to heat your water within a few minutes. They are also energy efficient since they consume less energy and power. They are an excellent replacement for storage heaters. We hope that our reviews of the best options available on the market will help you easily select one for yourself.

People Also Ask

You might have a lot of questions, especially if you’re buying a whole house tankless water heater for the first time. To clear up any uncertainty, here are some answers to frequent questions:

What Size of Tankless Water Heater Do I Need for a Family of 4?

A tankless water heater is of two types; gas and electricity heaters. For gas, the heater heats the water at 5.0 GPM (70⁰F), and for electricity, the heater heats the water at 2 gallons per minute (70⁰F). You should check your requirements first before buying a heater. The average rate of flow for showering is 2.5 GPM while it is 1.0 GPM for washrooms.

What Size of Tankless Water Heater Do I Need for a Family of 5?

A family of 5 will require at least 60 to 80 gallons of heated water. You need to know the temperature rise for selecting the perfect heater. For example, if you have a dishwasher at home, then the average rate of flow must be 1.5 GPM at 110⁰F. A washing machine will need the flow of water at 2.0 GPM. Thus, you need to consider the flow rate also.

How Does a Tankless Water Heater Work?

Tankless heaters do not require any storage tank for hot water. When you turn on the hot water tap, the heater will start working. The cold water will travel in the unit through the pipe. These heaters will work on electricity or gas supplies (elements). The water will heat up and will come from the tap.

How Long Does a Tankless Water Heater Last?

Tankless water heaters have a longer life expectancy than storage water tanks. They have a lifespan of 20 years or more. Storage water heaters have a shorter lifetime (10 to 15 years usually). You can also replace the parts and elements of the tankless water heater to extend its life expectancy.

How to Flush a Tankless Water Heater

1. For flushing, you need to turn off the electricity or gas supply that is heating the water.

2. Remove the cover plate using a screwdriver and close all the power supplies.

3. Now place the plate gain in its place. Close the valve that sends cold water to the heater and also turn off the main hot water tap.

4. Connect one end of the hose to the pond pump and the other to the cold water tap isolation.

5. Connect the other hose end to the hot water valve and the next one to a 5-gallon bucket of vinegar.

6. Then, using a wrench, tighten the couplers of the hose. Open the isolation valves and circulate the vinegar in the heater for 45 minutes. Close the cold water isolation and drain out the vinegar.

7. Turn on the cold water supply for five minutes. Now turn off the hot water valve and remove the screen (inlet filter). Wash the screen and reinstall it again.

8. Turn on both valves and other hot water taps in your house to remove any air bubbles, if present. Now check the leakages, if any, and turn on the breakers and gas supply.



My name is Bob Wells and I am a retired HVAC tech from Washington state. I am currently retired and no longer do much with HVAC, however, I feel like I have a lot of knowledge in the subject and I wanted to create a website where I could talk about what I've learned and help upcoming HVAC techs. Find more info about me and HVAC Training 101.