american condensing gas Water heaters are expensive. They only make sense for homes with high water heating needs
There are now very energy-efficient gas water heaters, with EF (Energy Factor) coefficients above 90%. Their name: condensing gas water heaters.
These water heaters may come as tankless or as tank-storage units, and have firing rates above 90.000 BTU/hour – two or three times more than common water heaters.
Which type to buy: condensing or standard gas water heaters?
Unfortunately, compared to standard gas water heaters, condensing units are very expensive, especially North-American models.
And that leads us to ask: do they worth the price?
The high output of gas condensing water heaters makes them well suited, for large domestic hot water needs. They are now standard in some European countries.
Small, average and Large uses
Condensing water heaters provide energy savings of, say, 20% or 30%. And that amounts, for average hot water consumption – baths, kitchen… - to about $100/year (average American homes, ACEE), that is, energy savings of $1.000 or more over the lifetime of the water heater.
That's a significant value but these savings may not be high enough for homeowners with low or average hot water needs. Condensing water heaters only become really appealing for big users, or in states/countries where prices have lowered significantly.
Condensing water heaters use a condenser to transfer more heat to the water: combustion gases travel a longer path before they exit the tank (see image at left, comparing a condensing water heater, at left, with a standard unit, at right). Some condensing water heaters have an Energy Factor (EF) of 96-98%, while the best standard units have a EF of 60-65% (in the USA).
Installation and Replacement
In new construction the installation of condensing water heaters is relatively simple and inexpensive...
But that's not the case when it comes to replacing a traditional gas water heater; condensing units require a condensate drain and a different type of venting (a sidewall-powered venting, or a combustion sealed venting), which makes the installation difficult and costly.