Lennox WHGS040T40NANS****

The registry lists a UEF, the ratio of hot water delivered to energy used, of 0.59 for this model. The registry does not state an annual figure. This site computed 188 therms of natural gas from that UEF and the DOE test's daily hot-water draw for the medium draw pattern. The source is DOE CCD, retrieved 2026-09-19. The figure applies only under that condition. The class is the 288 models registered as a gas tank at the medium draw pattern, and its median is 185 therms. This model sits 3 therms above that median. Its rank of 186th lowest puts it in the second-highest quarter of its class for energy use. The calculation steps are on the methodology page.

The first hour rating, the gallons of hot water available in the first hour from a full tank, is 68 gallons for this model. The rated volume is 38 gallons. The energy figure fits a household whose use matches the medium draw pattern, meaning a typical household's busy morning as that pattern defines it. It does not describe a household that draws more or less hot water than that pattern. For such a household the annual energy would differ, and its value is not available on this page. Nothing here covers another draw pattern for this model. To narrow options by fuel, space and size, use the water heater selector. To look up a same-class replacement by model number, use the replacement search.

Running cost is not in this text because it depends on the state average residential gas price, which differs by reader. The cost calculator takes a ZIP and applies that state's price to the 188 therms for this model at the medium draw pattern. Applying the same rate to 3 therms gives the yearly cost of the gap to the 185 therms class median. The installed price range on the page is a modeled installed-cost range, not a quote, and it has its own source and date. It is shown in a separate block and is not restated here. Every energy figure on this page is in therms of natural gas.