RELIANCE WATER HEATERS ATM-199M-N 1**

This site computes the 178 therms figure; the registry does not publish it. The calculation uses the registry's UEF, the ratio of hot water delivered to energy used, and the DOE test's daily hot-water draw for the high draw pattern. For this model the UEF is 0.95, from DOE CCD data retrieved 2026-09-19. The figure holds only at that federal test draw. The registry does not report this unit's energy use in any particular home. The steps are set out in how the annual cost is calculated. This model ranks 45th lowest in energy use among the 397 models in its class. That places it in the lowest quarter of its class.

The high draw pattern describes a larger household, or one where showers and laundry overlap. The registry lists this model's maximum flow rate in gallons per minute as 6. The 178 therms figure is a fair comparison point for a home whose hot-water use matches that pattern. It does not describe a smaller household. This page does not give the model's energy use at a lower draw pattern, so that value is not available here. The 4 therms gap to the class median also applies only among high-draw gas tankless units. To compare other fuels or sizes, use the selector by fuel, space and size. To check models in this same class, find a same-class replacement by model number.

This text does not state a running cost. The cost depends on your state's average residential natural gas price, so the page calculates it from your ZIP instead of giving a single figure. That calculation starts from the same 178 therms per year at the high draw pattern. At the test draw, this model uses 4 therms less gas than the class median described above. The value of that difference depends on your rate, and it is unknown until you enter your ZIP. Use the cost calculator on your own ZIP to see it. The installed price range appears in its own block on this page. It is a modeled range with its source and date, not a quote.