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Condensing vs. Non-Condensing Water Heaters


To the Point - Traditional tankless water heaters heat the water when called upon as it passes through a burn chamber without utilizing the thermal energy given off by the exhaust gases. Condensing units use that thermal energy of the exhaust gases by passing the water through an initial heat exchanger that houses those exhaust gases before they are pushed outside, thus preheating the inlet water before it enters the main burn chamber. In turn, condensing units operate at a lower BTU, raise the efficiency above 90%, as well as maintain the same gallon per minute when compared to similarly sized units.

Exhaust gases produced by a tankless water heater can reach temperatures upwards of 300°F, which is why traditional units require venting with non-corrosive metals (Category-3 Stainless Steel) to protect from condensation. This can become costly as most tankless water heaters do not come with the venting kit, though all EZ Tankless household water heaters do come with a venting kit. After figuring in the total distance of flue needed, you could be spending an extra $200-$500 after purchasing the unit. The exhaust gases exiting a condensing tankless water heater expel at a much lower temperature, usually around 100°F - 170°F, because most of that thermal energy is used to preheat the inlet water through the initial heat exchanger. Therefore, solid-core schedule 40 PVC/CPVC can be used to exhaust the remaining gases out of the home, which can be half or even a quarter of the cost of using stainless steel.

Not only is venting more cost effective with a condensing tankless water heater, but they’re also more efficient. All condensing tankless water heaters run above 90% efficiency, while non-condensing tankless water heaters usually run in the 80% range.


The cost of condensing units is currently greater than traditional, due to the second heat exchanger that raises the efficiency, but frankly… traditional units are on their way out. They have served us well and will continue to do so in portable and off-grid applications, but there’s no room in the home for them anymore. Condensing units are less expensive to vent, they operate at a lower BTU, and they’re overall more efficient… saving YOU the homeowner more money!