Condensing vs Non-condensing tankless water heater

Condensing vs Non-condensing tankless water heater

  • You have been surfing the internet and window shopping for a while. Finally, you have reached a decision to ditch your tank water heater for a tankless model, which is significantly more energy-efficient and less space-consuming. However, if you are still uncertain as to whether a condensing tankless water heater would serve you better than its non-condensing counterpart, this piece is for you. 
  • Don’t worry, you’re not crazy; you have actually got a genuine concern here. You cannot take a pick because your neighbor uses the same; you really need to make an informed decision. Hence this write will inform you of the major differences and similarities between a condensing and a non-condensing tankless water heater. 

What Exactly Is a Tankless Water Heater?

If you cannot associate with the group identified above, you may need to learn what tankless water is and what it does- a tankless water heater is exactly what it implies, a water heater without a tank. Traditionally, all water heaters come with tanks attached to them; at least, this is the model that was available a few decades ago.

However, just like everything advances in tech, it was thought that water heaters could use some improvements too; not only should they occupy less space in your home, but they should also be more energy-efficient and, consequently, more eco-friendly. 

It was also rightly perceived that you should never have to wait in the shower or at the wash-hand basin for water to get warm before you either take that shower or wash your hands. Hence, a tankless water heater was introduced. With a tankless water heater, you get several benefits, such as; compact sizes (occupying significantly less space), energy efficiency, and prompt or quick warming. 

If you are curious and wonder how the heating works in a tankless water heater, I got you covered. As rightly said, a tankless water heater has no tank to store heated water. Still, cold water supplied into the machine is heated when it passes through a heat exchanger, and the same water (now warm or hot) flows out and gets used directly without any storage.

The heat exchanger uses something called combustion to warm the water. Hence, as cold water passes through those extremely hot pipes, it gets warm and subsequently hot almost immediately. There are two major types of tankless water heaters: non-condensing tankless water heaters and condensing tankless water heaters.

Condensing vs non-condensing tankless water heaters

By now, you know that a tankless water heater heats water straight on demand without needing a storage tank. Now, permit me to add to that knowledge so you fully understand where the condensing function comes in. In order to heat water, a tankless water heater uses a heat exchanger to heat water hurriedly as it travels through the pipes of your unit.

However, this heating process needs to be more effective. Hence a secondary heating mechanism is utilized such that a secondary heat exchanger helps capture additional heat from the exhaust gases, now making the heating process more effective and quicker.

How a condensing tankless water heater works?

Cold Water Flow:

First of all, an inlet pipe attached to your tankless water heater unit passes cold water into the unit when a hot water tap is on. 

Heat Exchanger:

The heat exchanger is made of stainless steel and copper that is heated either by a gas burner or an electric heating element, depending on the type of your tankless water heater. Incoming cold water from the inlet passes through these heated compartments and becomes hot. 

Exhaust Gas:

The combustion process generates exhaust gases that contain heat energy. These gases are directed to a secondary heat exchanger in a condensing tankless water heater.

Condensing Process:

The exhaust gases do not just go to waste; the secondary heat exchanger traps them. The secondary heat exchanger then heats up water flowing around it, making water even hotter. 

Condensate Drain:

A condensing tankless water heater has a drainage pipe attached to it. This drainage pipe drains away the condensate produced in the condensing process of the unit. A condensate is merely the byproduct of the condensing process. 

Hot Water Delivery:

The now-heated water makes its way down the tankless water heater into the taps for your consumption. The whole process is repeated non-stop as long as there is a demand for hot water and the unit is activated for operation. 

In a nutshell, condensing tankless water heaters are quite energy-efficient because they are equipped to reheat your water. 

How A Non-Condensing Tankless Water Heater Works 

A non-condensing tankless water heater works in a similar fashion to a condensing unit. However, the major difference is that there is no re-heating. What this implies is that there is no secondary heat exchanger for re-heating. 

Water Flow:

Cold water enters the unit through an inlet pipe connected to the tankless water heater. This usually happens after you turn your tap on.

Heat Exchanger:

The cold water flows through a primary heat exchanger, typically made of copper or stainless steel. The heat exchanger contains a series of tightly coiled pipes or a heat transfer plate assembly. Hence, the heating process occurs when flames hit the copper or stainless steel pipes if the unit is gas-powered. If the unit is powered by electricity, an electric heating element produces heat in the pipes, turning cold water hot.

If you are looking to learn how an electric tankless water heater works, know that the core of its operation happens with the help of the heat exchange that happens with its in-built heat element. 

Hot Water Delivery:

The now heated water exits the tankless water heater and flows to the open hot water tap, providing instant hot water.


How does a tankless water heater reduce utility bills?

it heats water only when it is in demand which makes it immensely energy-efficient. This approach eliminates the standby energy loss associated with constantly keeping a large volume of water. 

What is the average lifespan of a tankless water heater? 

A tankless water heater usually lasts longer than a tank storage water heater because it carries no extra weight of a storage tank with it. When a tank is attached to your water heater, you may have to worry about tank corrosion and failure, but without a tank, as in the case of a tankless water heater, you are home and dry for a period of at least 20 years.

However, regular maintenance is key to keeping your tankless water heater healthy for quite a while. You may need to learn how to flush your tankless water heater and perform this routine operation.

Can a tankless water heater provide hot water to multiple fixtures simultaneously?

Yes, tankless water heaters are designed to simultaneously provide hot water to multiple fixtures. However, the capacity of the unit determines how many fixtures it can serve simultaneously. Higher-capacity models can handle greater hot water demand, allowing for multiple showers, faucets, and appliances to be used simultaneously without a significant drop in water temperature.

Are tankless water heaters suitable for larger households?

This depends largely on the hot water demand of such households and, indeed, the unit’s capacity, but ordinarily, a tankless water heater can serve a household irrespective of its size. However, if the hot water demand of a household is high, there may be a need to procure more than one tankless water heater. The available water heaters should be commensurate with your hot water need. Hence, you should not worry about what size of tankless water heater you need

Are Condensing tankless water heaters better than non-condensing heaters?

Tankless water heaters generally are more energy-efficient than storage tank water heaters. However, a condensing tankless water heater is even more energy-efficient because it is equipped with a secondary heating mechanism. Condensation on a water heater really provides it more efficiency.