When researching tankless water heaters, two terms appear frequently: condensing and non-condensing. Although both provide hot water on demand, their internal operation and installation requirements are not identical.

A non-condensing unit generally uses one primary heat exchanger. Combustion gases leave the unit at a relatively high temperature and require suitable high-temperature venting.

A condensing unit uses additional heat recovery. Exhaust gases pass through another heat-exchange stage, allowing more usable heat to be transferred to incoming water.

This additional heat recovery generally results in higher efficiency.

Venting Matters

Venting is one of the biggest practical differences. Condensing systems produce cooler exhaust and may use approved plastic venting materials. Non-condensing systems typically need metal venting capable of handling hotter exhaust.

Condensate Drainage

Condensing technology creates condensate as exhaust cools. Therefore, a drain arrangement is part of the installation. Non-condensing systems do not normally require this type of condensate drain.

Which Should You Choose?

There is no universal answer. Consider your hot-water demand, available installation space, existing venting, budget, expected energy usage, and local installation requirements.

For homeowners who want to explore the differences in more detail, this tankless water heater comparison is a useful resource: https://toptechmech.com/condensing-vs-non-condensing-tankless-water-heater/

A qualified professional should confirm the correct unit size and installation configuration before purchase.