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What is a Condensing Tankless Water Heater

When choosing a new water heater, it’s important to know the difference between a non-condensing and condensing tankless water heater.

Before we explain exactly what the difference between a non-condensing and condensing tankless is, it’s important that you understand, first and foremost, what a tankless water heater is. A traditional water heater stores hot water in its tank, but a tankless water heater does not have a tank. Instead, a tankless heater heats the water as its being used. Therefore, a tankless water heater provides you with an infinite supply of hot water, while a traditional water heater limits your hot water usage to its tank’s capacity.

Condensing TanklessCondensing Tankless Water Heaters

Condensing tankless water heaters are more efficient than their non-condensing counterparts. Let’s find out why. Condensing heaters have two heat exchangers, while non-condensing heaters only have one. The secondary heat exchanger reuses exhaust gas that heats the water. Before the water enters into the main heat exchanger, it has already been exposed to the heat from the exhaust gasses which allows the cold water to arrive at its desired temperature. Condensing heaters recycle the extra heat from the exhaust gasses and only vent it when it’s no longer useful for heating, which is at around 37 degrees celsius. This process of recycling heat allows for condensing units to have an efficiency level as high as 98%.

The ventilation for condensing heaters is not as expensive as for non-condensing heaters because their exhaust gasses are not nearly as hot. A standard PVC pipe can be used as venting for condensing units as it is able to withstand the heat and corrosiveness of the exhaust gasses.

Non-Condensing Tankless Water Heaters

Condensing units utilize their exhaust gasses to reheat the water by directing them inside the unit, non-condensing units vent the gasses directly outside. Non-condensing units heat the water using the gas burner and then vent the gasses out immediately. Due to this, it loses out on about 20% of the heat that would otherwise heat the water.

The exhaust gasses for non-condensing units can get extremely hot, up to 150 degrees celsius, and this requires much more specific venting materials than what is necessary for condensing units. The exhaust gasses from a non-condensing unit must be vented through heat resistant, corrosion resistant material. For this reason, It would cost significantly more to install venting for non-condensing units than for condensing units.

Which type should I get for my home?

We, as well as most people, would say that condensing tankless heaters are more effective and efficient at their job. Non-condensing units are less expensive to purchase than condensing units, but ultimately a condensing units can save you money in the long run due to their much higher level of operating efficiency. Condensing units are 10% to 15% more efficient than their non-condensing counterparts. A non-condensing unit would also come with some additional expenses related to the venting necessary for these units.

A non-condensing heater is slightly smaller than the condensing type, which allows for it to fit into smaller spaces. Non-condensing types require minimal maintenance by a professional technician, but do require an indoor combustion air. Condensing types, on the other hand, will require annual maintenance by a technician, but do not require indoor combustion air.

Essentially, there is a reason why both types of water heaters are available on the market as each have their own strengths and can adhere to different people’s needs and circumstances.


If you have any further questions regarding non-condensing or condensing tankless water heaters, or any of your other HVAC needs, don’t hesitate to contact DeMark Home Ontario today. We offer a free water heater installation done by our highly trained and experienced technicians. You’re saving more when you rent your water heater from DeMark Home Ontario. We have the lowest rental rates on the market and provide our customers with professional and reliable service. If you’re considering an upgrade to a new high efficiency tankless water heater for your home, DeMark Home Ontario is here to make the change as easy and convenient as possible. For more information, give us a call at 1 (855) 998-2998 or fill out our online request form and we will be happy to assist you.

Condensing Tankless Water Heater

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Notice for Power Vent Water Heater Customers

Effective August 2007, gas code requires technicians working on venting to replace black ABS vent pipe with white UL-certified vent pipe.

We will upgrade your venting pipes at no additional cost.

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