NAVIEN NHW700-180AI-NG

This site calculates the 209 therms figure; the registry does not publish it. We combine the registry's UEF, the ratio of hot water delivered to energy used, with the DOE test's daily hot-water draw for the high draw pattern. This model's UEF is 0.81. That rating comes from the DOE certification database (CCD), which we retrieved on 2026-09-19. The figure describes the unit under test conditions. It is not a measured bill from any home. Every model in the class is compared at the same test draw. The 27 therms gap to the 182 therms median therefore comes from differences in rated efficiency, not from differences in household use. See how the annual energy and cost are calculated for the inputs and steps.

The high draw pattern stands for a larger household, or one where showers and laundry overlap. This unit's registry listing gives a maximum flow rate in gallons per minute of 4.5. In its class of 397 gas tankless units at this draw pattern, it ranks 323rd lowest for energy use. That puts it near the high end of its class: most of the class uses less gas a year at the test's draw. If lower annual gas use matters most to you, you can compare other models in the same class with the replacement finder by model number. The registry data here does not show how this unit performs for smaller households or other draw patterns. That comparison is not available.

The running cost is not stated here because it depends on your state's average residential gas price. The page calculates it from your ZIP, using 209 therms of natural gas a year at the high draw pattern. At any gas price, the 27 therms gap above the 182 therms class median also shows up in the cost. At the same rate and draw, this model costs more to run than the median model in its class. A household that uses less hot water than the DOE test's daily draw would use less gas, and a heavier user would use more. This data does not say how large that change would be. To use your own rate, try the running-cost calculator for your ZIP. The installed price range appears in its own block on this page. It is a modeled range, not a quote.