Condensing
water heaters are one form of a high-efficiency water heater. With traditional
tank water heaters that make use of combustible fuels, a vent system must be
used which routes the exhaust gases from the combustion process safely outside
the building. The exhaust gas contains water vapor and is at a relatively high
temperature. Condensing water heaters recover much of that heat energy that
escapes up the vent pipe by using a secondary heat exchanger positioned in the
path of the exhaust gas. This process reduces the stack temperature of the
exhaust gas, causing the water vapor to condense back into a liquid as it
releases its thermal energy into the heat exchanger. Condensing water heaters
can be of both the traditional tank style or the tankless on-demand variety.
While they are more expensive to buy initially, they offer cost savings over
their operating life due to their higher efficiency.