Water heaters are becoming more energy efficient, with engineers working to maximize the amount of heat that is transferred from the combustion process to the water. Condensing technology is available in both tank and tankless water heaters — is designed to capture and reuse heat that previously went up the flue.
Condensing tankless water heaters offer efficiency gains of approximately 10 to 15 percentage points over conventional tankless units. Of course, they also carry the Energy Star label. Like any tankless water heater, condensing heaters are an on-demand system with no hot-water storage and no pilot light burning 24/7. When a hot-water appliance, faucet or fixture is turned on, the tankless system senses flow and rapidly heats the incoming water to the designated temperature. However long the fixture or appliance operates, the tankless unit will meet the demand for water at the set temperature; i.e., “endless hot water.”
A condensing unit uses the same sequence of steps to generate hot water as a conventional tankless water heater. But it also incorporates a secondary heat exchanger to capture and repurpose the heat generated from the combustion gases before they escape and are vented outside. In other words, instead of sending hot exhaust gases out the flue, which wastes energy, condensing heaters use this heat to preheat the incoming water. That’s why condensing gas water heaters are so efficient (up to 96 percent thermal efficiency).
The efficiency improvement might not be as drastic as switching from tank to tankless, but it certainly is not insignificant over the estimated 20-year life of a tankless water heater. If you’re looking to save energy, and you have a choice between 84 and 95 percent efficiency rating, wouldn’t you opt for the latter in most instances? If you’re interested in the latest and greatest in condensing tankless technology, you should check out the NRC711. On top of already existing benefits of condensing tankless units, the heater features a primary heat exchanger that is three times as durable, scale detection software for proactive leak prevention and a built-in digital display to aid servicing.
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