AMERICAN T-H3S-OS-N 1**

The registry lists this unit at a UEF, the ratio of hot water delivered to energy used, of 0.94. This site did not copy the annual figure from the registry. It computed 180 therms of natural gas from that UEF and the DOE test's daily hot-water draw for the high draw pattern, using DOE CCD data retrieved 2026-09-19. The figure applies only under that condition: a larger household, or one where showers and laundry overlap. A home that draws more or less hot water than the test assumes will use more or less gas than this. The methodology page explains how the calculation is built.

Against its class, the unit sits 2 therms below the median of 182 therms for 397 registered gas tankless models at the high draw pattern. Its rank is 165th lowest energy use of 397, which places it in the second-lowest quarter of its class. A gap of 2 therms from the median is small next to the 180 therms total, so the data supports calling it close to the class median rather than clearly apart from it. The maximum flow rate in gallons per minute is listed as 5.3. The temperature rise that value depends on is not available on this page, and the registry data used here does not say how many fixtures that flow can serve at once.

This figure suits households whose hot-water use matches the high draw pattern. It does not describe homes whose real use differs from the test draw, because 180 therms would then not apply to them. Running cost is not stated in the text because it depends on your state's average residential gas price, and this page assumes no rate. The cost calculator applies that price to 180 therms once you enter your ZIP. To look at another unit in the same class, you can find a same-class replacement by model number, starting from T-H3S-OS-N 1**. The modeled installed-cost range appears in its own block on this page with its source and date.