10 Best Tankless Water Heater For Radiant Heat 2022 – Review & Buyer’s Guide

Radiant floor heating is a straightforward mechanism. Many pipes sit beneath your house’s floor and supply warm water or electricity through the system to warm up the floor. 

This affordable and convenient method distributes warmth in the whole house. It continues to warm up the home even when the system is not working. The materials have thermal retention properties, so they gradually dissipate the warmth over time. 

If you are contemplating deploying the radiant floor heating system in your property, using the best tankless water heater for radiant heat would be an excellent option for various reasons. 

It can swiftly steam up the water, and it does not have to work to supply warm water continuously. They are armed with temperature sensors and heat exchangers, so you can rest assured that the water will be perfectly heated. 

On the other hand, if you use a standard unit, it won’t change its flame intensity or produce heated water instantly. So, it cannot compete with a tankless machine. 

A tankless device can save power costs and time invested in repairs and maintenance because they are packed with innovative technology. Additionally, they are highly energy-efficient and manufactured to last for the long-term. 

This article will list down our top ten best electric tankless water heater consumer reports to help you get an idea on which sort of unit you should pick for your residence.

10 Best Tankless Water Heater For Radiant Heat

1. Stiebel Eltron Tempra Plus 29 kW, Tankless Electric water heater – Best Overall

This best electric water heater for radiant floor heat is renowned as a “whole house” unit in the market. It features a compressed design so that you can hang it in any corner of the residence. 

It will supply hot water for all of your taps. The high-performance device needs 240v and 150 Psi for working efficiently. In one minute, it can produce 4.37 GPM and gives you the liberty to regulate the temperature between 86 degrees Fahrenheit and 125 degrees Fahrenheit. 

It is an electric unit, so it does not require vents. It heats the water through coils instead of burners. Furthermore, it flaunts a digital interface that permits you to control your water temperature according to your needs. 

A dial selector is present that is super-easy to use and allows you to personalize your warm water delivery to your precise specifications. The brand claims that this product will lower your energy bills by 15 to 20 percent.

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2. Rinnai RUR Series Sensei SE+ Tankless Hot Water Heater

The Rinnai RUR Series Sensei SE+ best tankless water heater for radiant heat is armed with ThermaCirc360 technology that delivers hot water quicker with an integrated recirculation pump. 

Timer and thermal bypass valve are also incorporated in it. That’s why; this unit is highly suitable for houses that don’t have a dedicated return line. There is no need to wait for a long time to get warm water. 

This appliance can proficiently cater to the needs of the entire house. You can run multiple faucets at once. Moreover, it works only when you need hot water, saving money on utility bills. The compact design makes the installation convenient. 

You can deploy it in any non-traditional place in your house or office. Built-in smart technologies such as WIFI monitoring empower you to monitor your unit’s efficiency and address problems before they become worse. 

High-quality materials are used for manufacturing this product, so you can expect to take advantage of it for up to 20 years.

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3. Rinnai RUCS75iN Tankless Water Heaters

Rinnai RUCS75iN best hot water heater for radiant heat features an energy factor of 0.93 and a uniform factor of 0.90. It is deliberated for interior deployment as it arrives with condensing technology and two heat exchangers that enhance its energy-efficiency and resilience. 

Its minimum and maximum heating power are 10,300 BTU and 160,000 BTU per hour, respectively. Stainless steel material is used for making the heat exchangers. 

This tankless heater weighs only 63 Lbs. As it has a compacted design, so you are free to hang it at your desired location. Additionally, it utilizes natural gas and produces 7.5 GPM. What makes it stand out is its Control-R Wi-Fi Module. 

It allows you to monitor your unit 24/7 and address the issues at the right time before they become un-repairable. It includes combustion air intake pipe and fittings, and the termination vent screens are 3” polyethylene. You can expect to use this model for up to 20 years.

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

Takagi T-H3-DV-N best electric tankless water heater for cold climates can be used for commercial and residential properties. It is compliant with rules of Ultra-Low NOx. Grade copper alloy is used for developing its heat exchanger’s tubing. 

As it is designed for indoor installation, so it is well-suited for heavy residential properties as well. It can supply limitless hot water for up to three showers in colder climates at the same time. However, in summers, you can get water for four showers. 

It is an excellent choice for radiant floor systems, storage tanks, and hydronic systems. You can set it to support a maximum of four units by using the easy-link feature. However, by using the multi-unit control, you can link up to 20 devices. Also, it can provide up to 10 GPM with gas input of 199,000 BTU.

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5. Ecosmart ECO 18 Electric Tankless Water Heater

It is one of the top electric tankless water heaters that are presently available in the market. It works proficiently, so you can expect it to provide a higher level of convenient user experience. 

This product generates only 2.5 GPM, so it is suitable for a small-sized family. In warmer climates, it can deliver unlimited water for up to two showers. But in winters, it can support only one shower at a time.

As it features a compact size, so it will use less energy, which means you can save a lot of money on energy bills. Moreover, its installation process is more straightforward, and you can hang it yourself, but we recommend hiring professional services. 

Ecosmart ECO 18 integrates a self-modulating technology so that the device will mechanically sense the groundwater’s flow and temperature. 

The heater detects if the water is being heated at the accurate temperature range. It takes a 30-second delay to fix the water temperature before distributing it to your sink or tap.

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6. Rinnai RU199iN Tankless Water Heaters

Rinnai RU199iN is the best tankless water heater for radiant heat that flaunts a higher flow rate of 11 GPM. As it features a higher flow rate, so it will empower you to organize your residence with several fixtures effortlessly. 

Furthermore, you can get hot water for two showers at once. It arrives with a straightforward system that has a fast heating option. It consumes minimum 15,000 BTU units and maximum 199,000 BTU units. 

This machine is intended to function with constant support. It means that you can acquire never-ending water for your house. To steam the water quicker, the brand has integrated a revolutionary heating mechanism that allows you to obtain the fastest heating options. 

You can set a recirculation pattern. Besides, it incorporates Circ-logic technology that is identical to water recirculation. As a consequence, there is less water loss, so it is an excellent unit to use.

The best electric water heater for radiant floor heat has a 40-gallon tank that may seem larger, but it is compressed and space-efficient in reality. Its maximum length is only 31 inches, and the overall weight is 64 pounds, which makes the installation procedure more straightforward and manageable. 

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7. Rheem RTEX-18 18kW 240V Electric Tankless Water Heater

Rheem RTEX-18 comes with a compressed design that allows you to hang it at a smaller place. It is a powerful and environment-friendly unit that can generate 4.4 gallons of water in just 60 seconds. 

You can put it under the sink, in the bathroom, or near the kitchen counter. According to the best electric tankless water heater consumer reports, this device is easier to install. 

There is no need to find a special location to deploy it, thanks to its smaller size. The product dimensions are 4″x15″x19″ only. Besides, it boasts an attention-grabbing design so that it won’t destroy the beauty of your house. 

Rheem has inserted digital temperature controls, so you can conveniently set the desired water temperature in 1 degree Fahrenheit increments ranging from 80 degrees Fahrenheit to 140 degrees Fahrenheit. 

The most noteworthy trait is that it is 99.8% energy-smart. When the unit connects, you may experience flickering of LED light bulbs. To solve this issue, you can deploy glowing bulbs.

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8. Rinnai V75IN Indoor Tankless Hot Water Heater

Accomplishing utmost energy efficiency is the ultimate goal of modern homeowners. This best tankless water heater for radiant heat can cater to all your requirements effortlessly. 

One of the primary reasons why this model is on our list is that it creates nominal emissions. It is a gas-fired device, but you can hang it anywhere you want without distressing about destructive gases, thanks to its concentric venting system. 

Furthermore, this energy-efficient machine utilizes 40% less power than a tank-style heater. It is packed with innovative technology that locks in the heat and prevents accidental transformations to the water temperature. 

The energy factor of Rinnai V75IN is 0.82. It operates proficiently as a complete house appliance for small and medium houses. It vaunts sturdy and efficient coils that generate hot water for multiple applications. 

It can warm up the water to the highest temperature of 160 degrees F and only needs 0.4 GPM for the startup. Despite being capable of generating 7.5 gallons per minute, this heater is relatively slower. 

According to trutankless water heater reviews, it takes almost 1 minute before hot water flows from the fixture. 

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9. iHeat Tankless S-16 240V 66A 16KW Stainless Steel

The iHeat best electric water heater for radiant floor heat can produce 3.5 GPM, which means you can get hot water for two showers and one sink simultaneously. It can handle multiple applications in the warmer weather but can support only one activity in colder climates. 

Stainless steel is used for its construction. It is a perfect device for all activities near the ocean, small boats, resorts, and other outdoor areas. The best thing about it is that it can be used in commercial settings such as hotels, clinics, hospitals, and schools.

The machine features a compact design that is eye-catching at the same time. You can fix it under the sink or in the closet or attic as per your requirements. Furthermore, it is energy-efficient and uses a lower amount of energy. 

You can anticipate to save up to 60% on your heating expenditures. It’s waterproof built allows you to control the temperature with the help of interactive touchpad. It is the most affordable best tankless water heater for radiant heat on our list.

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10. Stiebel Eltron Tempra Plus 36 kW, Tankless Electric water heater

Stiebel Eltron Tempra Plus 36 kW can produce a flow of 7.5 GPM at an incoming water temperature of seventy degrees Fahrenheit. So, it is an excellent whole-house heater. At full power, it utilizes only 36 kilowatts of electricity at 240v, and 150-amp draws. 

A 300-amp electric service is required to run it safely. Additionally, three double pole 50-amp breakers are needed, but if possible, go higher for extra security. On the front side, you will observe a dial that allows you to fine-tune the temperature effortlessly. 

To ensure your safety, the brand has integrated anti-scalding technology that averts the machine from creating hot water that reaches scalding levels. Besides, it is equipped with advanced flow control technology, so you get a steady temperature with fluctuating flow rate. 

The manufacturer’s customer support is excellent, you can get in touch with them at any moment if you experience any problem with your heater. It helps you save up to 15 to 20% on your water heating expenses. 

Best of all, the best electric tankless water heater for cold climates is covered by two guarantees. The anti-leak warranty will last for seven years, and the heating and electric components guarantee will last for three years. 

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Buying Guide For The Best Tankless Water Heater For Radiant Heat

History of radiant floor heating system

Radiant floor heating is an old concept that has been present for centuries. The first version of this system was installed in the Ottoman Empire in the 1400s. 

At that time, in Turkish bathrooms, elevated floors were made that permitted the warm air to flow beneath the floor. In the second iteration, electrical cables were placed underneath the floor. 

It is installed in small spaces because it consumes a high amount of energy that costs a lot of money. The third iteration is energy-efficient, and nowadays, it is trendy. 

It is very much identical to traditional radiator heating but applied differently. This method allows you to heat your whole house and ensures you will always put your feet on a hot floor on a cold morning. 

It is an exciting idea, but before purchasing the best electric tankless water heater for cold climates, grab information about how radiant floor heating system works.

How Radiant Floor Heating System Works?

Bendable PEX tubes are deployed on your subfloor’s top. These tubes work well because they can bend as required and don’t have joints as well. They are positioned around nine inches apart and protected to the subfloor in the entire house or wherever you want to install it. 

The tubing’s both ends are connected to a manifold. Then, dry-tamped mortar or concrete are placed on the subfloor’s top and PEX tubes to cover the layer. These substances are utilized frequently because they are capable of holding the heat for extended durations. 

If you have utilized any of these materials, it is better to use ceramic tiles as the finished floor layer because they can hold onto heat exceptionally. The tubing passes water from the manifold to a heating system. 

It equally distributes the water through the tubes to deliver constant heat in all rooms. The circulating pump is responsible for pulling the water from the system and returning it to the heater for reheating. 

As the water flows around the system, it does not lose a lot of heat—10 degrees only. The device does not have to work harder to keep the water warm enough to heat the residence uniformly. 

The warm water flows under the floor and warms up the concrete. That heat is shifted into tiles, and then, it is released out into the rooms.

How To Select The Best Hot Water Heater For Radiant Heat?

Power Source

Tankless units come in two different types: gas and electric. Gas ones rely on natural gas or propane, and the electric ones use electricity. The electric devices further have two types: point of use and whole-house. 

The first ones are designed to supply water to a sink or shower only. However, the whole-house ones will provide hot water for the entire house. Electric heaters are smaller and can be deployed in any non-traditional place, but they have a little flow output.

On the other hand, gas machines feature a higher flow output, but they demand professional installation. The gas-fired heaters are a better option for many of you, but remember that all of them have older models equipped with on/off switch and the newest models armed with modulating technology.

Performance And Heating Power

It is necessary to pick the best electric hot water heater for radiant heat that provides adequate heat. Gas heaters’ heating power is measured in BTUs, and electric heaters’ power is measured in kilowatts (1,000 watts).

The higher the kilowatts or BTUs, the more heating output the unit will have. We advise you to pick the one that has the highest power. 

Self-Modulating Technology

The best electric water heater for radiant floor heat should be equipped with self-modulating technology. It will produce hot water by using the lowest amount of electricity or gas. They will have valves that have diverse opening and closing processes. 

Cost

Cost is the most critical factor that must not be ignored during the tankless device’s selection process. You will have to spend anywhere from $6000 to $14000 on the radiant heating system, but the cost can vary based on square foot. 

Tankless units are expensive than tank-style ones, but they are energy-smart and work only when you need hot water.

GPM

While buying a heater, don’t forget to consider its total GPM. GPM refers to how many gallons of hot water the tankless appliance can produce in one minute. 

If a heater has a 10 GPM flow rate, it means you will get 10 gallons of water in 60 seconds. The flow rate will vary from heater to heater because each model is unique. There are heaters available that provide 1 to 20 GPM.

Warranty

The best tankless water heater for radiant heat comes with different types of warranties. Therefore, you should closely check the terms and conditions defined with these guarantees to choose the right device.

Generally, the tankless units have limited warranties starting from 6 to 20 years. Some offer lifetime warranties as well. Many manufacturers provide guarantees for the overall heater, parts, labor, heating components, or all of the mentioned things. 

If the machine offers a lifetime warranty, then the house owner will enjoy free replacements for the unit during his lifetime. Look for an appliance that provides an extended and most inclusive guarantee.  

Frequently Asked Questions