Condensing vs Non-Condensing Tankless Water Heaters!

With so many water heaters out there on the market, you’ll want to be able to make the best decision for yourself when picking one. Thus, we’re here to help you find out the perfect choice for your home and lifestyle, when it comes to condensing vs non-condensing tankless water heaters. First, we’ll look into each of these types and see how they work exactly.

How Do Tankless Water Heaters Work?

With the input of power into the machine, the intake pipe brings in water, and the mechanism begins to heat up. A flow sensor picks up this change, and notifies the control panel to do so.

The primary heat exchanger pulls the heat from the burner, where the heating process is started. As the heat is pulled in, it heats the water in the tubes surrounding the heat exchanger.

In order to prevent the water from becoming too hot, a mixing valve will occasionally spritz in a little cold water. As the water leaves this chamber, the temperature sensor will ensure you have the desired temperature of water. 

Both the models we have to show you today have different mechanisms in certain places that make them worth the look, and you’ll find those out soon!

Condensing Tankless Water Heaters

Condensing Tankless Water Heaters

How Does A Condensing Tankless Water Heater Work?

Condensing tankless water heaters were created as an innovative method, in order to help address some common issues in other types of water heaters, especially open system ones. Not to mention, they were seen to be much more efficient and convenient when it came to heating water, making them quite a popular choice.

The innovation in condensing tankless water heater systems came from the implementation of the second heat exchanger, which allowed to create a loop system in which the water would be heated. First, the water is heated through the primary heat exchanger, and the steam (exhaust gasses) that form, are circulated through to the second heat exchanger.

After this, the exhaust gasses, usually around a 100 degrees Fahrenheit, is used to warm up the incoming cold water. Attaining heat from both the heat exchangers, allows for water to be heated up faster, and with less energy wasted.

This mechanism also has the benefit of having the vapor that had been created to cool down and be resupplied back into the water supply. Ultimately, this makes the system efficient. Condensing tankless heaters are quite useful to have in your home, in case you do decide on it!

Non Condensing Tankless Water Heater

Non Condensing Tankless Water Heater

How Does A Non Condensing Tankless Water Heater Work?

From the understanding of a condensing tankless water heater, you’ll find that the Non-condensing version is a much easier process to follow. If you’re switching from the traditional version of water heaters, then you’ll notice that most people switch to this version of water heater to start with.

Non condensing tankless water heaters heat the water in the same way as their counterpart, but the primary difference is that they have only one heat exchanger. The primary heat exchanger in this version heats the exhaust gasses to be much hotter. The ventilation for this system is also quite different, as the gasses are not looped back around, but instead are vented out of the unit entirely.

You’ll find that most models of gas tankless water heaters are non-condensing tankless water heaters, as they are much more popular. So, it definitely shouldn’t be too hard to find a great one!

Pros and Cons of Condensing vs Non Condensing Tankless Water Heaters

Condensing Tankless Water Heater


  • These heaters are very efficient, up to 90% on average
  • Materials used and required for ventilation tends to be cheaper than other variants


  • Constant condensation of vapor results in accelerated corrosion

Non Condensing Tankless Water Heater


  • Initial investment of changing from traditional to non condensing is cheaper
  • Can use already built features of traditional heater
  • Does not require professional maintenance
  • Smaller size


  • Extremely hot exhaust can ruin cheap ventilation systems
  • Lower efficiency than Condensing heater models (around 80%)
  • Higher investment to revitalize already built components

Condensing or Non-Condensing Water Heaters?

Now that you know the benefits and detriments of both of these types of models, it is up to you to make the best choice for yourself. However, at the end of the day, what type of water heater you choose, mainly depends on the needs in your home. That being said, let’s look at some of the most important factors!


You’ll find that the condensing version tends to be more expensive than the non-condensing version. However, that is mainly because of the second heat exchanger required in the first mentioned version. The condensing heater will in time be worthwhile with its higher efficiency, but the initial cost of the non-condensing heater may be more viable for most people.


Condensing heaters are far superior than the non-condensing version, as they have 90% efficiency compared to the 80% of the latter mentioned. They are both still very efficient, so not to worry!


In this case, you really can’t have the perfect winner, as gas heaters are built to last for two decades. Both mechanisms have issues with specific parts that will degrade before the other, but both will last you for a long time.


Q: Which is better, condensing or non-condensing tankless water heaters?

A: In terms of efficiency, condensing units are better with their 90% efficiency, compared to the non-condensing version’s 80% efficiency. However, there are other factors that can change your pick.

Q: Are condensing water heaters worth it? 

A: Condensing water heaters are built to last for a long time, with high efficiency and key innovative features that make them very ergonomic and optimized. If you can pay the initial cost fee which tends to be a bit high, you’ll see great returns in time.

Q: How do you vent a non-condensing tankless water heater?

A: Non condensing tankless water heaters require ventilation to get the exhaust gasses out. There are two types: Direct Vent and Power Vent.

Credit for the video – Same Day Hot Water Service – Sydney & Wollongong

The Takeaway

Hopefully you managed to get a good understanding when it comes to condensing vs non-condensing tankless water heaters, and that you can make the choice with a lot more ease.