AMERICAN T-H3M-OS-N 1**

The registry lists a UEF, the ratio of hot water delivered to energy used, of 0.91 for this unit. It also lists a maximum flow rate in gallons per minute of 3.5. The registry does not publish annual energy. This site computed 122 therms of natural gas from that UEF and the DOE test's daily hot-water draw for the medium pattern. The figure comes from DOE CCD data retrieved on 2026-09-19. The comparison group is the 80 models registered as a gas tankless unit at the medium draw pattern, and its median is 135 therms. This unit sits 13 therms below that median, at 4th lowest of 80. That places it in the lowest quarter of its class for energy use.

The figure suits a household whose hot-water use resembles the medium draw pattern, described as a typical household on a busy morning. For that use, 122 therms is the number to compare with the 135 therms class median. It does not suit a household whose use differs from the medium pattern. The figure was computed for the test's daily draw, not measured in any home. Energy use at other draw patterns is not available for this model on this page, and this page does not estimate it. The rank of 4th of 80 applies only within this class, so it says nothing about units of another type or fuel.

The running cost is not stated here because it depends on your state average residential gas price. The cost calculator applies that price, found from your ZIP, to the 122 therms for this unit. Because the price depends on the state, the 13 therms gap to the class median has no single cost value either. The methodology page explains how the annual cost is calculated. To compare against another unit registered at the medium draw pattern, you can find a same-class replacement by model number. The installed price range appears in its own block on this page, with its source and date.