Condensing vs Non-Condensing Tankless Water Heaters

Condensing vs Non-Condensing Tankless Water Heaters

Finally, you’ve decided to purchase a tankless water heater. It’s a terrific idea to get rid of the tank water heater, which takes up more room and causes additional issues such as tank leaking, running out of water, and so on. And to make things even easier, I created this guide on the two types of tankless water heaters. By the end of this article, you should be able to choose the best tankless water heater for your needs.

Types of Tankless Water Heaters

The key distinction between these two types is how exhaust gases are handled by them during operation.

Non-Condensing Tankless Water Heater

A non-condensing tankless water heater, is a type of water heating system that produces hot water on demand without the use of a storage tank, like a condensing tankless water heater.

It lacks advanced methods for recovering heat from exhaust gases, leading in lower energy efficiency.

Non-condensing tankless water heaters are often powered by natural gas or propane and can provide a constant supply of hot water, but they may struggle to meet high hot water demands in bigger houses.

They also have a shorter lifespan than condensing tankless water heaters and may require more maintenance due to mineral deposits accumulating inside the system.

Condensing Tankless Water Heaters

A condensing tankless water heater is a type of water heating system that employs modern technology in order to achieve high energy efficiency and lower energy expenses.

It works by heating water as it flows through a heat exchanger on demand, eliminating the need for a storage tank.

The condensing feature recovers heat from exhaust fumes and uses it to warm up incoming cold water, resulting in a greater efficiency rating.

Condensing tankless water heaters are often powered by natural gas or propane and may deliver a continuous supply of hot water, making them excellent for high-demand households.

They also outlast standard tank water heaters and take up less space in your home due to their small form.

Efficiency and Cost

Energy efficiency is a major concern when deciding between a condensing and non-condensing tankless water heater. Condensing units often have efficiency ratings of 90% or greater, whereas non-condensing units have ratings of 80-85%. This implies that condensing units use less energy and can save you money over time.

However, because of their more complex construction and additional components, condensing units have a greater initial expenditure than non-condensing units. A condensing unit may cost twice as much as a non-condensing unit in some instances. This initial cost can be offset by long-term energy savings, but when making a purchasing choice, it is critical to consider the payback period.

The cost of installation varies based on the type of unit and the complexity of the installation. Condensing units might require additional venting and piping, raising installation costs. However, both types of tankless water heaters are often easier to install and less disruptive than classic tank-based systems.

Installation and Maintenance

Tankless water heaters, both condensing and non-condensing, require professional installation to ensure optimal performance and safety. Mounting the unit, connecting the water and gas lines, and installing the venting system are common installation steps.

Periodic flushing is required for both types of tankless water heaters to eliminate mineral buildup, which can affect performance and efficiency. Condensing units, on the other hand, may necessitate more frequent maintenance due to their more complex structure and additional components. To maintain optimum performance and to enhance the lifespan of the device, it is critical to follow the manufacturer’s maintenance requirements.

Potential problems and maintenance differ between condensing and non-condensing devices. Non-condensing units are more likely to have burner and heat exchanger issues, whereas condensing ones may have problems with the secondary heat exchanger or condensate drain. To reduce the possibility of problems and ensure optimal operation, it is critical to select a renowned brand and have the unit serviced by a competent technician.


When deciding between a condensing and non-condensing tankless water heater, consider energy efficiency, cost, installation, and maintenance requirements. Condensing units provide greater efficiency and possible long-term cost savings, but they are more expensive to purchase and may require more frequent maintenance. Non-condensing units are typically less expensive in the beginning but have lower efficiency ratings. Finally, the ideal option will be determined by personal preferences and circumstances, therefore it is crucial to conduct research and speak with a trained specialist before making a selection.


Can you drink water from tankless water heater?

No, drinking water directly from any form of water heater, including tankless water heaters, is not advised. While tankless water heaters can supply hot water on demand for a variety of applications, they are not intended to cleanse or filter water. Before using the tankless water heater, the water supply should be checked and treated to ensure that it is safe for consumption. If you are concerned about the quality of your water supply, it is best to seek advice from a water treatment professional or your local health authority.

Can a hot water heater burst?

Yes, under some conditions, a hot water heater can burst. This can happen if there is a considerable buildup of pressure inside the tank, which is usually caused by a faulty pressure relief valve or temperature and pressure relief (TPR) valve. When water is heated, it expands, and if the pressure within the tank exceeds its capacity, it can rupture or explode and cause a fire.

Can bacteria grow in tankless water heater?

If correct maintenance and cleaning procedures are not followed, bacteria can form in tankless water heaters. The heat exchanger’s warm and wet environment can be a great breeding ground for germs like Legionella. Regular flushing and cleaning can help to avoid bacterial growth and ensure the tankless water heater’s safe operation. If you are concerned about bacterial growth in your tankless water heater, it is critical that you follow the manufacturer’s maintenance requirements and consult with a certified professional.

Does hard water damage tankless water heaters?

Yes, due to mineral buildup in the heat exchanger and other components, hard water can potentially damage tankless water heaters over time. Hard water minerals, such as calcium and magnesium, can build up and lower the effectiveness of the unit, causing corrosion and shortening its lifespan. Regular flushing and descaling can help to reduce the effects of hard water while also improving the performance and longevity of the tankless water heater.

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This Post Has 4 Comments

  1. Maier Zaman

    Great info.