AMERICAN ATO-140B-N 1**

The figure of 137 therms is not a registry entry. This site computed it from the registry's UEF, the ratio of hot water delivered to energy used, which is 0.81 for this unit, and from the daily hot-water draw that the DOE test assigns to the medium draw pattern. The source is the DOE CCD, retrieved 2026-09-19. The comparison group is the 80 models registered as a gas tankless unit at this draw pattern. Their median is 135 therms, so this model sits 2 therms above it. Its rank is 52nd lowest energy use of 80, which places it in the second-highest quarter of its class for energy use. The data on this page do not explain the gap.

The registry also lists a maximum flow rate in gallons per minute of 3.6 for this unit. That is a separate measurement from annual energy, and it does not change the 137 therms figure. The energy figure describes a typical household on a busy morning, which is what the medium draw pattern represents. For any other daily usage, a value for this model is not available on this page, and it is not estimated here. A reader who wants a unit ranked better than 52nd in the same class can use find a same-class replacement by model number to look at other registered models.

The running cost is not written in the text because it depends on the state average residential gas price, which differs from reader to reader. The cost calculator on your own ZIP applies that price to 137 therms. The steps behind the calculation are described in how the annual cost is calculated. The same price also converts the 2 therms difference from the class median of 135 therms into a yearly cost gap for the medium draw pattern. If your household's hot-water use differs from that pattern, the calculated cost will differ from what you actually pay.