Boiler vs. Tankless Water Heater

Boiler vs. Tankless Water Heater – Comparison Guide in 2023

Hot water is essential to every household, just as it’s essential to have an appliance capable of supplying it. While searching for your ideal hot water provider, you’ll encounter two units often used for that purpose: boilers and tankless water heaters.

Undoubtedly, those two units have their own advantages and disadvantages. In this article, we’ll review some of the top boilers and tankless water heaters to get a better idea of which one’s best. Let’s begin our boiler vs. tankless water heater review, shall we?

Boiler vs Tankless Water Heater – Comparison in 2023

Boilers Overview

Boilers are a necessary appliance for many households, as they’re responsible for supplying the radiated heating system installed. After mounting a boiler, you’ll have a proper hot water supplier to distribute heat as needed, be it across a single room or through the house.

With the many boilers available, finding the right one could be tricky. Nonetheless, we’ve gathered five of the best ones out there. These devices are efficient, user-friendly, and, better yet, long-lasting units worth the investment.

Here, we’ll review some of the top boilers to see what they can do. We’ve gathered a selection of units from the most popular brands, including Rinnai and Noritz.

1) Rinnai Q205SN Natural Gas Boilers

The first condensing boiler is a unit from Rinnai, one of the most popular brands out there. This unit works on natural gas, offering many venting options for single-pipe settings for room air, and systems featuring a two-pipe structure.

Due to its compact, wall-mounted design, setting up this boiler consumes barely any space. The stainless steel construction guarantees an efficient performance for many years to come, delivering an incredible heat exchanger for most households.

This unit comes with a built-in modulating pump and a reset sensor for outdoor installations. These features are inside the box to keep them protected.


  • Efficient performance on natural gas
  • Many venting options available
  • Compact design for wall-mount installation
  • Includes a modulating pump


  • Dull aesthetic design

2) Rinnai M-Series Natural Gas Condensing Boiler

If you like Rinnai as a brand, here we have another one of its top boiler series for you. The M-Series units are condensing boilers that, much like the previous pick, work on natural gas too. In total, there are eight units included in this line of products.

Although they have some slight differences, the M-Series boilers share a lot more similarities between each other. For instance, they’re all compact, and they work on natural gas or propane.

The electrical consumption of these units varies from 185W to 191W. Also, the max capacity (MBH) varies depending on the unit too. While some of the boilers work at 57 (17kW), others go as high as 148 (43kW).


  • Flexible venting options offered
  • High-quality stainless steel build
  • Compact to save space
  • Built-in modulating pump


  • The design is not the best

Related Comparison: Noritz vs. Takagi – Tankless Water Heater

3) Noritz CB199-DV-NG Combi Boiler

The CB199-DV-NG is the perfect representation for Noritz’s incredible CB line of combi boilers. This unit has a 95.1% AFUE rating, providing around 9.2 gallons of hot water per minute.

This unit weighs 85 pounds, which is less than the standard boiler. Setting it up isn’t difficult, allowing DIYers and inexperienced homeowners do install the boiler by their own hand. Once you set it up, the boiler’s stainless steel construction prevents damage from corrosion.

You can also operate the unit safely. The boiler has several built-in security measures, such as sensors for flame, gas, and water. Additionally, there are prevention mechanisms for overheating and scald.


  • Beautiful condensing gas boiler
  • High energy-efficient performance
  • Provides up to 9.2 GPM
  • Safety measures


  • Heavyweight unit

4) Rinnai i150SN Condensing Gas Boiler

When the brand’s quality is undeniable, it isn’t surprising to see several of its appliances included in this list. The i150SN condensing gas boiler is a rather expensive heat-only model, but its performance could make it worth the money for you.

The unit comes with an outdoor reset and a built-in modulating pump to secure the boiler’s performance outside. While operating, the boiler delivers an input rating that reaches 150k BTUs, requiring either natural gas or propane to function.

Another interesting feature of this boiler is the quality of its build. For instance, the unit features Rinnai’s unique self-cleaning stainless steel, offering an incredible heat exchanger and an additional flat plate heat exchanger.


  • Useful features for outdoor applications
  • Works on 150,000 BTU
  • Operates on either gas or propane
  • Self-cleaning build


  • The unit makes noises while operating

5) Westinghouse Condensing Heating Wall Mount Boiler

Having a good-looking boiler is only one of the benefits of purchasing this boiler. This gas condensing boiler offers hot water throughout the house working at 140,000 BTUs. Also, there’s a storage tank included for additional domestic hot water if needed.

Installing this unit won’t be much of a problem for anyone. Due to its wall-mounted design, homeowners will be able to save plenty of space once they set up the boiler. Also, the universal piping location allows moving the installer connection from the left to the right side of the unit.

With a stainless steel build, this appliance is capable of providing a high-quality performance for many years to come. Another advantage is the ultra-low NOx combustion system, which improves the boiler’s performance significantly.


  • Good-looking boiler
  • Works on powerful 140,000 BTU
  • Easy installation
  • Ultra-low NOx emissions


  • Customers reported plenty of faulty components

Tankless Water Heater Overview

The tankless water heater rise to popularity has been possible due to the incredible performance put up by these units. They provide on-demand or instant hot water flow, which you can use to supply different areas, appliances, and fixtures around the house.

Among the reasons homeowners prefer the tankless water heater is because of how energy-efficient they are, and their compact design. Once set, these machines will keep the household well supplied with water while still saving you some money.

Next, we’ll discuss some of the highest quality tankless water heaters available in the market as of this moment. Much like we did with the boilers, we’ve considered the most popular brands and their products.

6) Ecosmart ECO 18 Electric Tankless Water Heater

There are many reasons why one would consider this tankless water heater among the most innovative ones out there. On the first impression, it’s a beautiful, compact unit that consumes barely any space, and it blends well with most decorations at home.

For its build, the heater features copper and steel components. Installing the unit is a simple process, and operating it afterward is even easier. The interface is intuitive and user-friendly for anyone.

Depending on your needs, you can adjust the digital temperature control increasing on 1 degree. You can set the temperature in a range from 80°F to 140°F.

Once installed, the unit is capable of heating a couple of sinks and a pair of showers simultaneously. The self-modulating technology featured is incredible, as it provides endless hot water with 99.8% energy efficiency.


  • Beautiful unit with digital display
  • Adjustable temperature
  • Supplies sinks and showers at the same time


  • The fuse blows out easily due to power outages

7) Rinnai V Series HE Tankless Hot Water Heater

Outdoor tankless water heaters must be durable to withstand the environments. Luckily, Rinnai takes that into consideration, and they create high-quality units that work well and last for a long time. The V65eN model is a clear example of that.

This unit is for outdoor installation only. It operates on natural gas, and the different venting options ensure you’ll find a suitable installation method for your household. Although this unit isn’t Energy Star compliant, it’s still capable of saving energy.

Fortunately, if you don’t want an outdoor appliance, you can go for the Rinnai V64IN instead, which is an indoor mount unit.


  • Durable build for outdoor applications
  • Compact design
  • Saves energy
  • Provides up o 6.5 GPM


  • Some of the instructions are not clear

8) Stiebel Eltron Tempra 29 Plus

If you want the best results, you’ll need appliances capable of delivering them. The Stiebel Eltron Tempra is an outstanding heater with advanced features, such as the thermostatic temperature control, that will allow you to adjust the settings with accuracy to get those results expected.

And the accurate temperature provided by the unit is possible due to frequent readings received by flow and temperature sensors. Once the sensors work their magic, you can set the water between 86°F and 140°F. Meanwhile, the heater takes care of modulating the power to keep the temperature stable.


  • Advanced features like thermostatic temp control
  • Flow & temperature sensors
  • Adjustable temperatures
  • Compact design


  • Hard to install

9) Rinnai RU Series Sensei SE+

This tankless water heater is for indoor applications. It belongs to Rinnai’s popular RU Series Sensei SE+, which is a line of products that offers the other seven units in total. The RU Series includes fan-favorites like the RU130in and the RU160in.

For now, let’s talk about the RU199in model. This model offers up to 11 GPM, securing constant hot water for different areas in the household. The Circ-Logic technology featured makes it possible for homeowners to set recirculation patterns, which should be helpful, as it activates the unit when needed.


  • Powerful performance delivering 11 GPM
  • Options to set recirculating patterns
  • Durable build


  • Since it requires plumbing and carpentry, and electric work, homeowners may need assistance from a professional to install this unit

10) Noritz NRC66DVNG Indoor Hot Water Heater

The NRC66DVNG heater from Noritz weighs slightly lower than 40 pounds, making it easy to maneuver and set up. After installing it, the unit offers a flow rate capable of providing 6.5GPM, which is suitable for different applications such as residential or commercial purposes.

This device includes modern heat exchanger technology combined with an integrated controller, two features that secure an incredible performance. Another convenient feature of this unit is that you can schedule the working time as you see fit.

And the leak-proof design, along with the many venting options available, make this heater a versatile and durable choice for many. Additionally, while working, the unit saves both energy and water as much as possible.


  • Comfortable weight
  • Provides 6.5 GPM
  • Option to schedule working time
  • Leak-proof design


  • Not the most appealing unit

What Are the Differences between Boiler and Tankless Water Heater?

Deciding between a boiler or a tankless water heater depends on several conditions. For instance, you want to know the climate conditions around the house, and whether or not there’s enough space for the units. While most tankless heaters are compact, boilers could consume more space.

You also have to figure out which areas the appliance has to serve. Boilers are often the better choice to supply different rooms simultaneously.

Another difference between boilers and tankless water heaters is how each unit handles the water. Do you want your water stored, or on-demand? For the first, boilers are the way to go. As for the latter, you may want to consider getting a tankless water heater instead.

Lastly, many people would argue that the tankless heaters are far better than the boilers when it comes to saving energy, and thus, money. These units use energy efficiently, reducing waste to a minimum amount.

So, as you can see, both units share plenty of similarities, but they’re quite different too. Ultimately, it’s your decision to pick the appliance that accommodates your household best. Then, you’ll be ready to start enjoying the advantages of either one.

Final Words

Discussing boiler vs. tankless water heater allows homeowners to understand which is the better appliance for their households. As seen here, there are many options, and each one works better under different circumstances.

Once you figure out what you need exactly, you can proceed to consider the options available in that category and choose the most suitable appliance for your house, whether it’s a boiler or a tankless water heater.

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