Condensing vs. Non-Condensing Tankless Water Heaters

February 13, 2023

Maybe your traditional tank model water heater has finally given up, or you need to heat water without constantly running out.

Whatever the reason, if you’re looking for a tankless water heater for your home, you’ve no doubt come across references to condensing and non-condensing models.

But what exactly is the difference between the two, and how do you know which is better for your home? Read on, and we’ll answer the most important question: what is the best water heater for my home?

How Do Condensing Tankless Water Heaters Work?

A condensing tankless water heater takes advantage of the water vapour in the exhaust gas with an extra heat exchanger. It’s designed to loop exhaust gases back into the system, recycling the additional heat.

In addition to the primary heat exchanger that heats cold water, the secondary heat exchanger transfers the excess heat from the hot gases into the water. This lowers the temperature of the steam gases, which produces condensation inside the water heater.

The condensing technology neutralizes the acidic condensation by going through corrosion-resistant channels inside the unit.

A condensing tankless water heater will save you money by using residual exhaust heat, instead of having to produce extra heat to maintain the desired temperature.

How Do Non-Condensing Tankless Water Heaters Work?

Non-condensing systems get rid of the steam that builds up with non-corrosive venting materials. This type of tankless hot water heater only has one heat exchanger, and the hot exhausting gases leave the water heater at incredibly high temperatures (upwards of 148C/300F).

Most natural gas-powered tankless hot water heaters are non-condensing models. If you’re going from a traditional tank water heater, this is typically the type of tankless heater that people choose because it can use your home’s existing ventilation system.

However, a downside to a non-condensing tankless water heater is that it’s far less efficient than condensing units. The heat that’s lost in the venting process of non-condensing units is wasted energy that could be recycled. This means you spend more money and energy heating than you would with a condensing unit.

However, non-condensing tankless water heaters are still far more efficient than traditional water heaters, so it’s still a good option if you’re looking to spend less energy and money overall.

Is Condensing Better Than Non-Condensing?

When your tankless system heats water, the exhaust gases produces condensation or steam during the heating process. The steam is cooled inside the unit and condenses. This condensation water can corrode whatever it touches because it’s acidic.

Energy Efficiency

If energy efficiency is one of your main reasons for switching to a tankless water heater vs. a tank model, a condensing unit will outperform a non-condensing unit. This is because a second heat exchanger works to recycle energy that otherwise would be lost in a non-condensing water heater.

Installation

Non-condensing tankless water heaters are usually smaller, and don’t have to drain the collected condensation water (which is acidic). This makes them the more flexible option when it comes to where you choose to install it. However, you’ll have to use expensive venting material (made of corrosion resistance material) due to the higher temperature and acidity of the exhaust gases.

A condensing tankless water heater needs a condensate drain, and potentially a condensate neutralizer, although they will exhaust cooler gases and are able to use more inexpensive venting material such as standard PVC pipe.