In terms of water heaters, what does the term "condensing" refer to?

The term "condensing" in the context of water heaters specifically refers to high-efficiency systems that utilize the heat from combustion gases that would typically be vented outside. In a condensing water heater, the exhaust gases are cooled down to the point where water vapor condenses into liquid water, releasing latent heat in the process. This recovered heat is then used to preheat the incoming water, allowing the system to operate at higher efficiencies compared to traditional water heating methods that emit these gases without utilizing their residual heat.

By capturing this additional energy, condensing water heaters can achieve efficiency ratings significantly above those of standard models, often exceeding 90%. This means they can provide more heat per unit of fuel consumed, which can lead to lower energy costs and a reduced carbon footprint.