GSW WATER HEATERS T-H3S-DV-N 1**

This unit's registered UEF is 0.95. UEF, the ratio of hot water delivered to energy used, is the registry's value; the annual figure of 178 therms of natural gas is not. This site computed it from the registry's UEF and the daily hot-water draw that the DOE test assigns to the high draw pattern. It therefore describes the federal test's conditions and not a particular home. The source is DOE CCD, retrieved 2026-09-19. A household that uses more or less hot water than the test draw will see a different total. The calculation steps are set out on the methodology page.

Among the 397 models registered as a gas tankless unit at the high draw pattern, this one has the 45th lowest energy use, which places it in the lowest quarter of its class. Its 178 therms sits 4 therms below the class median of 182 therms. The registry lists a maximum flow rate in gallons per minute of 5.4 for this model. The high draw pattern is the situation of a larger household, or one where showers and laundry overlap. The comparison does not apply to a household whose use matches a different draw pattern, because the class is defined only within the high pattern. The data here does not state how the flow rate translates into delivered temperature at a given inlet water temperature. For choices by fuel, space and size, the water heater selector takes those inputs.

The running cost is not written in the text of this page. It depends on the state average residential gas price, which differs by where the reader lives. The 178 therms figure is fixed at the test's daily draw, and the cost follows once a local gas rate is applied to it. The cost calculator does this from the reader's own ZIP, and this page gives no cost estimate of its own. For a same-class swap, the replacement finder searches by model number, such as T-H3S-DV-N 1**. The registry data holds no metered use from homes, so how closely 178 therms matches use in a given household is unknown.