Lennox WHGS040S40NPXS****

The figure of 173 therms is not a registry entry. This site computed it from the registry's UEF, the ratio of hot water delivered to energy used, which is 0.64 for this model. It also used the daily hot-water draw of the federal test for the medium draw pattern. The source is the DOE CCD, retrieved 2026-09-19. Because the figure depends on that test draw, it describes the model under test conditions and not a particular home's use. The registry lists a rated volume of 39 gallons for this tank. The calculation is set out on the methodology page.

Among the 288 models registered as a gas tank at the medium draw pattern, this unit ranks 44th lowest for energy use. That places it in the lowest quarter of its class. Its 173 therms is 12 therms below the class median of 185 therms. The comparison holds only for that draw pattern. A household whose hot-water use is heavier or lighter than the medium pattern should not read 173 therms as its own annual use. The registry gives a first hour rating, the gallons of hot water available in the first hour from a full tank, of 71 gallons. This page does not say whether that covers a given household's peak demand. To filter models by fuel, space and size, use the water heater selector.

The running cost is not stated here because it depends on the reader's own rate, the state average residential gas price. The cost calculator takes a ZIP and applies that price to 173 therms. The result changes with location, while the energy figure stays the same for the medium draw pattern. The modeled installed-cost range appears in its own block on this page with its source and date. It is a modeled range, not a quote. Energy use for other draw patterns is not available for this model on this page and is not estimated here. To look for a same-class model by model number, use the replacement finder.