TAKAGI T-H3M-OS-N 1**

The registry lists a UEF, the ratio of hot water delivered to energy used, of 0.91 for this model. This site combined that UEF with the DOE test's daily hot-water draw for the medium pattern to compute 122 therms. The registry does not publish that annual figure itself. The inputs come from DOE CCD, retrieved on 2026-09-19. Among the 80 models registered as a gas tankless unit at the medium draw pattern, this one ranks 4th lowest in energy use. That puts it in the lowest quarter of its class, 13 therms below the class median of 135 therms. The comparison holds only for the medium pattern.

The figure fits a household whose hot-water use resembles the medium pattern, a typical family on a busy morning. For that use, 122 therms is the number to set beside another model in the same class. The registry gives a maximum flow rate in gallons per minute of 3.5. That value describes how much water the unit can deliver at once, not how much gas it burns. The annual figure is for natural gas only. Energy use at other draw patterns, or on another fuel, is not available on this page, so it should not be read from 122 therms. To find a same-class unit by model number, use the replacement finder.

The running cost is not written out here because it depends on your state's average residential gas price. Two households with the same 122 therms will pay different amounts if their gas rates differ. The cost calculator on your own ZIP applies your state's rate to this model's figure. The steps behind that calculation are described in how the annual cost is calculated. The 13 therms gap from the class median of 135 therms is an energy difference at the medium pattern. The cost of that gap depends on the same rate, and this page does not estimate it.