Lennox WHGS040S40*PXS****

The figure of 173 therms is natural gas use, computed by this site rather than taken from the registry. The registry lists a UEF, the ratio of hot water delivered to energy used, of 0.64. The site combines it with the DOE test's daily hot-water draw for the medium draw pattern. The figure holds only for that condition. A household that draws more or less hot water than the federal test will use a different amount. The source is the DOE CCD, retrieved 2026-09-19. The tank has a rated volume of 39 gallons.

Against the 288 models registered as a gas tank at the medium draw pattern, this unit sits 12 therms below the class median of 185 therms. Its rank is 44th lowest energy use of 288, which places it in the lowest quarter of its class. Its first hour rating, the gallons of hot water available in the first hour from a full tank, is 71 gallons. The comparison suits a household close to the medium draw pattern, a typical three- or four-person household, checking one gas tank against its peers. It suits less a household whose use is well above that pattern, because the data here does not show how a 71 gallon rating meets that household's peak. The water heater selector filters by fuel, space and size.

The running cost depends on the state average residential gas price, so it is not stated in this text. Multiply the 173 therms by your own gas rate, or enter your ZIP in the cost calculator, which uses your state's price. The methodology page explains how the annual cost is calculated. The installed price range appears in its own block on this page as a modeled range, not a quote, with its source and date. To look for a unit in the same class, the replacement finder searches by model number. Actual use in a home is not measured here, so 173 therms is a standard-test figure and not a forecast for one household.