AMERICAN ATO-199B-N 1**

The figure of 206 therms is computed by this site, not published by the registry. It combines the registry's UEF, the ratio of hot water delivered to energy used, of 0.82 with the DOE test's daily hot-water draw for the high draw pattern. The source is the DOE CCD, retrieved 2026-09-19. Among 397 models registered as a gas tankless unit at the high draw pattern, this model has the 229th lowest energy use. That places it in the second-highest quarter of its class for energy use. Its figure sits 24 therms above the class median of 182 therms. The method behind the calculation is set out in how the annual cost is calculated.

The high draw pattern describes a larger household, or one where showers and laundry overlap. The registry lists this unit's maximum flow rate in gallons per minute as 5. The data used here does not show whether that flow meets a particular household's simultaneous demand, so this page draws no conclusion on it. A household that uses less hot water than the test's daily draw would use less than 206 therms, and one that uses more would use more. No household-specific estimate is available. A reader who wants gas use closer to the class median of 182 therms at this draw pattern can look for a same-class replacement by model number.

Running cost is not stated in the text, because it depends on the state average residential gas price where you live. The cost calculator for your own ZIP applies that price to 206 therms at the high draw pattern. The 24 therms gap to the class median converts to cost at the same price per therm, but the amount depends on that price. The modeled installed-cost range appears in its own block with its source and date. It is a modeled range, not a quote, and it is not repeated here. If you are still narrowing units by fuel, space and size, the water heater selector covers those inputs.