AMERICAN STANDARD WATER HEATERS GSN40T2-3-*

The 188 therms figure does not appear in the registry. This site derives it from the registry's UEF, the ratio of hot water delivered to energy used, which is 0.59 for this model. It combines that value with the daily hot-water draw that the DOE test sets for the medium draw pattern. That pattern stands for a typical household on the federal test, not for any measured home. The registry data come from the DOE CCD, retrieved 2026-09-19. If your household uses more or less hot water than the test assumes, your use will not match the 188 therms figure. The data do not show how large that difference would be. The steps behind the figure are set out in how the annual cost is calculated.

Within its class, this model ranks 186th for lowest energy use among the 288 gas tank models registered at the medium draw pattern. That places it in the quarter of the class just above the median given above. The registry lists a rated volume of 38 gallons. It also lists a first hour rating, the gallons of hot water available in the first hour from a full tank, of 70 gallons. These figures are useful for checking a unit for a household close to the medium pattern. They cannot show whether the unit suits a household with heavier morning demand. That check would need the household's own peak-hour use, which is not in the data. To compare other models in the same class, use the same-class replacement search by model number.

The text on this page gives no running cost. The cost of 188 therms of natural gas a year depends on the average residential gas price in your state, so the page calculates it from your ZIP. The same applies to the 3 therms gap to the class median. What that gap costs depends on your rate, and this page gives no estimate of it. You can work out both on your own rate with the water heater cost calculator for your ZIP. The installed price is shown in its own block with its source and date. It is a modeled installed-cost range, not a quote, and this text does not repeat it. Neither figure accounts for a gas price other than your state average or for use outside the medium pattern.