AMERICAN ATO-180B-N 1**

The annual figure 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 registry does not publish the annual number itself. This site computes it, and the DOE CCD record was retrieved on 2026-09-19. The result applies only to natural gas and only at the federal test's daily draw. Actual use in a home depends on real hot-water demand, which the registry data does not include, so 206 therms is a basis for comparison and not a forecast of one household's use. The steps are set out in how the annual cost is calculated.

Among the 397 models registered as a gas tankless unit at the high draw pattern, this unit ranks 229th lowest energy use of 397. That places it in the second-highest quarter of its class for energy use, with 206 therms against a class median of 182 therms. Its maximum flow rate in gallons per minute is 4.7. The data here has no class comparison for flow rate, so this page makes no statement on how 4.7 compares. The unit fits a larger household, or one where showers and laundry overlap, if that flow rate meets the demand. It is a weaker match for anyone who puts lowest energy use first, since models below 182 therms exist in the same class. A same-class replacement by model number or the selector by fuel, space and size can narrow the options.

Running cost is not written here because it depends on your state's average residential gas price. Multiply 206 therms by your local price per therm, or enter your ZIP in the cost calculator, which applies that price for you. The same method prices the 24 therms gap between this model and the class median of 182 therms. Both figures hold only at the high draw pattern; this page has no values for other draw patterns. 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 in this text.