NAVIEN NPE-180S2

This site calculated the 176 therms figure; the registry does not publish it. We combined the registry's UEF, the ratio of hot water delivered to energy used, with DOE's daily draw for the high pattern. This model's UEF is 0.96, as listed in DOE's Compliance Certification Database, retrieved 2026-09-19. The figure holds only at the federal test's daily hot-water draw, not at your household's actual use. The registry gives no figure for other daily draws, so use at your own draw is not available here. Each step of the calculation is set out in how the annual cost is calculated.

Among the 397 models registered as a gas tankless unit at the high draw pattern, this one ranks 12th lowest for energy use. That places it in the lowest quarter of its class, consistent with the gap to the median noted above. The high draw pattern describes a larger household, or one where showers and laundry overlap. Its maximum flow rate in gallons per minute is 4.4, as listed in the registry. The registry does not state whether 4.4 covers a given home's overlapping fixtures. A household with a smaller daily draw falls outside the pattern this 176 therms figure describes. To compare other units, use the water heater selector by fuel, space and size.

This page states no running cost in the text, because the cost depends on your state's average residential gas price. The page computes it from your ZIP, applying that price to the 176 therms figure at the high draw pattern. At any one gas price, the 6 therms gap below the class median carries through to a lower running cost. To run the numbers on your own rate, open the water heater cost calculator for your ZIP. The installed-cost range shown elsewhere on this page is a modeled range, not a quote, and carries its own source and date.