A. O. SMITH ATM-199M-N 1**

The figure of 178 therms is computed by this site, not published by the registry. It starts from the registry's UEF, the ratio of hot water delivered to energy used, which is 0.95 for this model. The site then applies the DOE test's daily hot-water draw for the high draw pattern. The result applies to natural gas and to that condition only; a household that uses more or less hot water than the test will use a different amount. The source is DOE CCD, retrieved 2026-09-19. Against the class median of 182 therms, this model sits 4 therms lower, and its rank of 45th lowest among 397 places it in the lowest quarter of its class for energy use.

The high draw pattern describes a larger household, or one where showers and laundry overlap. The listing gives a maximum flow rate in gallons per minute of 6. The registry data used here does not show whether that flow covers a specific household's fixtures running at the same time, so this page makes no such claim. A household with lower hot-water demand than the test's daily draw is not represented by the 178 therms figure. The class comparison of 397 models also does not cover other draw patterns or other fuels. For those cases, the water heater selector filters by fuel, space and size.

The running cost is not stated in this text, because it depends on the state average residential gas price, and that differs by reader. The cost calculator applies the price for your ZIP to the 178 therms figure under the high draw pattern. The steps are set out in how the annual cost is calculated. The 4 therms gap to the class median of 182 therms is also in therms, so it converts to a cost only with the same gas price. To compare this unit with another model of the same class, find a same-class replacement by model number. The rank of 45th lowest among 397 is based on energy use alone and says nothing about price.