Tankless Water Heater For Radiant Floor Heat – Detailed Reviews

Looking for another alternative to generate the hot water while keeping your electricity bills low? You should definitely consider radiant floor heaters. Not only it is economical but also energy efficient. Here we are going to list down our top three tankless water heater for radiant floor heat in this review so that you can get the idea on which kind of tankless water heater you should go for.

Product Name




Tankless water heater for radiant floor heat

Natural Gas

  • Max BTU: 199,000
  • Flow Rate: 10 GPM
  • Dimensions: 11.2 x 17.8 x 24.9 inches
  • Weight: 59 lbs


Price: $$$$$


  • Flow Rate: 2.5 GPM
  • Dimensions: 17 x 14 x 3.5 inches
  • Weight: 11.25 lbs


Price: $$$

Natural Gas

  • Max BTU: 140,000
  • Flow Rate: 6.6 GPM
  • Dimensions: 20.3 x 13.8 x 6.7 inches
  • Weight: 38 lbs


Price: $$$

Reviews: Tankless Water Heater for Radiant Floor Heat

1. Takagi T-H3-DV-N Natural Gas Tankless Water Heater

Tankless water heater for radiant floor heat

The tested model is simply the best tankless water heater for radiant floor heat and the one that deserves the first position. You will get a gas-powered unit which is outstanding when it comes to the hot water supply. It is efficient and based on the latest technology.

With this model, you can enjoy the maximum flow rate of 10 gallons per minute, so this particular tankless water heater is used for more advanced users. We must point out that Takagi is one of the best brands in the business and their models are more than just popular at the moment. You will always have plenty of hot water and you can use this model literally anywhere.

Powered by Natural Gas

This is the first and the main feature of the tested unit. Because it uses gas to heat the water, there is no need for massive electricity consumption. Of course, it still requires electricity to operate, but the power consumption is below the minimum. As we have mentioned, you will get 10 gallons per minute with this unit. Let’s just add the fact that you must install it indoors. This is the official recommendation by the manufacturer.

Fully Computerized Safety Features

Some of you might believe that electric tankless water heater for radiant heat isn’t very safe to use. Well, with this model, this is completely opposite. It comes with the latest safety features and even better, they are computerized, so you don’t have to worry about anything. All you can do is throw your worries behind your back and enjoy the hot water that this heater provides. 


  • 10 gallons per minute flow rate
  • High quality of the tested unit
  • Energy efficient
  • Advanced safety features
  • Suitable for colder climates


  • User may face complications while doing the installation
  • Strictly for indoor use only

2. Ecosmart 18 Electric Tankless Water Heater

The electric water heater radiant floor heat we have here is slightly different than the first model. As a matter of fact, it is more than just different and it is a fully electric model. But, this manufacturer is known for ultra-efficient models and this one isn’t different.

It offers 2.5 gallons per minute, it is based on the latest technology and it is going to last. In reality, this may be one of the most durable models of this kind available on the market and definitely the one that makes a huge difference. We know that the water flow looks low, but it is actually sufficient for two showers or a shower and a sink.

Self-Modulating Technology

This isn’t the brand new technology, but it is one of the most appealing when it comes to tankless water heaters. What it means is that the unit uses the most appropriate or the lowest amount of energy at any given moment in order to heat up the water. Thanks to it, we are looking at 99.8% energy efficiency, which is stunning in the lack of a better word. Ecosmart is already a known brand when it comes to energy efficiency, so if this is the main factor for you, then this is the best model for your house.

For Water with 62 Degree Fahrenheit and Above

If you are planning to use this particular model, you must know that it is rated for climates where the temperature of the water is 62 degrees Fahrenheit or higher. In those situations, it will power a shower and a sink without an issue. When the temperature of the water is 70 degrees Fahrenheit, you can use it for two showers at the same time.


  • Self-modulating technology
  • 99.8% energy efficiency
  • Superior quality
  • Requires very little space to be installed


  • For climates where the temperature of the water is 62 degrees Fahrenheit minimum
  • Water flow rating

3. Takagi T-K-Jr2-IN-NG Natural Gas Tankless Water Heater

With the 6.6 gallons per minute of a water flow, the tested unit is above the average if we compare it with most, other models. In the lack of a better word, this particular version is more than just great. It uses natural gas and it will meet even the highest requirements. In essence, it is small, yet powerful version which has it all and which can be used for more than just ordinary applications. Don’t forget that some venting will be required. As a matter of fact, we are looking at the stainless steel class III ventilation of 4 inches. This is an additional investment, but at least you are going to have a worry-free and affordable way to get all the hot water you will ever need.

144.000 BTU

The heater on this particular model has a BTU rating of 144.000 which is impressive. Yes, there are higher values present as well, but not in this price range. Considering the capabilities and the overall power, the tested model is above the average. It is more than sufficient for all average users. And this heat exchanger has a warranty of 10 years.

0.81-0.83 Energy Factor

If you are looking for a tankless water heater that offers the best performances for the money and still comes at a reasonable price this one is for you. As you can see, the energy factor is 0.81-0.83 or one of the best in the class. The chances are high that this will make you want one as soon as possible.


  • Efficient model
  • 144.000 BTU
  • Great value for money
  • 6.6 gallons per minute of water flow


  • Requires ventilation
  • Average durability

Buyer's Guide

In our buyer's guide, we will list down all the features and factors that must be taken into consideration when looking for radiant floor tankless water heater. After going through this article, we do hope that you will be able to determine which model is best suited for your expectation. 

Power Source

Here we can see that there are two main types. You can choose between a tankless water heater which uses gas or propane and the ones that use electricity. The second type can be furthermore divided into two categories. Point of use and the whole house. Point of use will feed just one sink or shower with hot water. The whole house will obviously provide hot water for all sinks, showers, and faucets in that home. Electric units are extremely small and they can be installed under a sink, but they have lower hot water flow output.

Gas-powered units offer a much higher water flow, but they are more complicated to install. They obviously use gas, but there are two versions. The ones that use natural gas, and those that run on propane. For most of you, natural gas models are a better choice. Keep in mind that all of them can be divided into older (models that have on and off switch) and newer which use modulating technology.

Self-Modulating Technology

The hot water heater for radiant floor heat must come with self-modulating technology. As the name suggests, you will be able to use a device which is clever or capable of adapting. In simpler words, this means that the water heater will use the lowest amount of gas or electricity to heat up the water. They use a valve which features different open or closed processes.

Gallons per Minute Flow

As you may recall, we have mentioned this factor several times in our reviews and this is an essential factor if you are thinking about using water heater to heat the house. It refers to the water flow per minute. For example, we have a model that offers 10 GPM. It obviously means that 10 gallons of hot water is available per a minute. This amount will vary and it is unique for each model. You can browse models between 1 and 20 GPM.

Energy Efficiency

Another factor which has to be taken into consideration. How efficient your new tankless water heater is? At the moment, gas-powered, models with a tank have 67% efficiency. A tankless is much better with 80%. Some are even rated at 99.9%, which is impressive. All this means that you will save money on a monthly basis. On average, you are looking at 30-60% of money saving by installing a tankless water heater. This may be higher or lower and it will depend on the tankless water heater itself and the use of hot water. We must say that in this case scenario, more is better.


You were able to see that some models require specific ventilation. This refers to the gas-powered units only. It is an added expense when installing the unit, but it is a one-time investment and it isn’t as expensive as you may believe. Nevertheless, keep in mind that you will have to make some adjustments to the installation place.


Some units can be installed indoors and outdoors, while others must be installed indoors only. Make sure to use the manufacturer’s recommendations or you can damage the unit, which isn’t a smart thing to do and repair will cost you!

If it isn’t installed properly, you will lose a warranty, which is the second main issue here. Hence, it is advisable to seek professional for installation.


One of many reasons why a homeowner will choose a tankless water heater is the space saving. We all know that these models are the best when it comes to the amount of space they require. In order to get the best one, look for dimensions and the installation place at your home.

Final Verdict

Takagi T-H3-DV-N Natural Gas Tankless Water Heater

The best tankless water heater for radiant floor heat is the Takagi TH3 Natural Gas. This model has the most impressive flow rate, it is well-made and it comes with all you are going to need. As such, we must rate it with 5 stars out of 5. It is the safest choice as well.

Other models on the list are more on purpose-based and they may be the best choice for some of you. Anyways, all 3 units are leaders in their ranges and they are based on the latest technology.

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