AMERICAN STANDARD WATER HEATERS GSN40L2-3-*

The registry lists this model as a gas tank with a UEF, the ratio of hot water delivered to energy used, of 0.6. This site computed the annual energy, not the registry. It combined that UEF with the daily hot-water draw the DOE test uses for the medium draw pattern. The source is DOE CCD, retrieved 2026-09-19. The result is 185 therms of natural gas per year. The model ranks 89th lowest in energy use of 288, which places it in the second-lowest quarter of its class. The difference from the class median is 0 therms, so on this measure it uses the same energy as a typical model in that class.

The first hour rating, the gallons of hot water available in the first hour from a full tank, is 64 gallons. The rated volume is 38 gallons. The 185 therms figure holds only for a household that matches the medium draw pattern. A household that draws more hot water than the test assumes will use more gas than that figure. A household that draws less will use less. The registry data does not show how any one household compares. It cannot confirm that the first hour rating covers your busiest hour. For a different household size, the selector by fuel, space and size filters models on those inputs. At 0 therms from the class median, this model has no energy advantage or penalty within its class at the test draw.

Running cost is not stated in this text. It depends on the state average residential gas price, and this page has no price for your location. The cost calculator on your own ZIP applies that price to the 185 therms figure for this model. How the annual cost is calculated is documented separately. The result changes with your rate, but the gas quantity at the medium draw pattern stays at 185 therms. The modeled installed-cost range is shown in its own block with its source and date. It is a modeled range, not a quote. If you need a same-class replacement, you can find one by model number using GSN40L2-3-*.