RELIANCE WATER HEATERS ATO-180B-N 1**

This site calculates the 206 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 daily hot-water draw that the DOE test sets for the high pattern. The registry lists a UEF of 0.82 for this model in DOE CCD data retrieved 2026-09-19. Among the 397 gas tankless models registered at the high draw pattern, it ranks 229th lowest in energy use. That puts it in the second-highest quarter of its class for energy use. You can check each step on the page about how this site calculates annual energy and cost.

The high draw pattern stands for a larger household, or one where showers and laundry overlap. The registry lists this unit's maximum flow rate in gallons per minute as 4.7. The 206 therms figure describes a home whose daily hot-water use matches the test's high pattern. A smaller household that draws less hot water falls outside that case. This data has no energy figure for lower use. The same is true for a home that draws more than the test's daily volume. To check this model against others registered at the high pattern, use the same-class replacement search by model number.

The text on this page gives no running cost. The cost of 206 therms of natural gas a year depends on your state's average residential gas price. For that reason, the page calculates the cost from your ZIP. The cost of the 24 therms gap between this model and the 182 therms class median also depends on that price. The cost calculator for your own ZIP converts both into figures at your rate. Those figures still assume the federal test's high draw pattern. The installed-price range shown elsewhere on this page is a modeled range with its own source and date, not a quote.