AMERICAN ATHR-199M 1**

The registry lists a UEF, the ratio of hot water delivered to energy used, of 0.95 for this model. This site combined that UEF with the DOE test's daily hot-water draw for the high draw pattern. The registry does not publish the annual figure; this site computed it. The result is 178 therms of natural gas a year at that test draw. The source data is DOE CCD, retrieved 2026-09-19. The methodology page explains how the annual cost is calculated. A different draw pattern would give a different annual figure, and none is shown here.

Among the 397 models registered as a gas tankless unit at the high draw pattern, this one ranks 45th lowest in energy use. That places it in the lowest quarter of its class. Its annual use is 4 therms below the class median of 182 therms. That gap is the only distance from the median the data provides. The high draw pattern describes a larger household, or one where showers and laundry overlap. The registry lists a maximum flow rate in gallons per minute of 5.9. The temperature rise that flow assumes is not available in this data. So whether that flow covers overlapping showers and laundry in a given home is not shown here.

This energy figure is not a running cost. Cost depends on your state's average residential gas price, and this text states no price. The cost calculator applies your own rate, using your ZIP, to the 178 therms shown here. A modeled installed-cost range, with its source and date, appears in its own block on this page. A household that uses less or more hot water than the federal test's daily draw will use a different amount than 178 therms. That household's actual use is not available in this data. For another model in the same class, find a same-class replacement by model number.