NAVIEN NHW700-180AE-NG

The 209 therms figure is computed by this site, not the registry. It combines the registry's UEF, the ratio of hot water delivered to energy used, of 0.81 with the DOE test's daily hot-water draw for the high draw pattern. It applies to natural gas at that test draw only, from DOE CCD data retrieved 2026-09-19. The method is set out under how the annual cost is calculated. Against the 397 models registered as a gas tankless unit at the high draw pattern, this model sits 27 therms above the class median of 182 therms. Its rank of 323rd lowest energy use of 397 puts it in the highest quarter of its class for energy use.

The registry lists a maximum flow rate in gallons per minute of 4.5 for this unit. That is a rated ceiling, and the data here does not show how it changes with incoming water temperature. The high draw pattern stands for a larger household, or one where showers and laundry overlap. For that kind of use, this model's 209 therms is 27 therms more than the class median of 182 therms. A reader who puts flow rating first can note the 4.5 figure. A reader who puts gas use first may compare models ranked ahead of 323rd, which you can find through the same-class replacement finder by model number. Household use outside the test draw is not available in this data.

Running cost is not written on this page because it depends on your state's average residential gas price. The cost calculator applies that price, taken from your ZIP, to the 209 therms figure for the high draw pattern. Because this model is 27 therms above the class median of 182 therms, its cost at any one gas price is also above that of a median unit at the same test draw. The installed price range is shown in its own block with its source and date, as a modeled installed-cost range, not a quote. If you are still narrowing options by fuel, space and size, the water heater selector covers those. This page has no figure for actual field use.