A. O. SMITH GUC 40 4**

This site calculated the 264 therms figure; the registry does not list it. It combines the registry's UEF, the ratio of hot water delivered to energy used, with the DOE test's daily hot-water draw for the high draw pattern. For this model the UEF is 0.64. The registry data comes from DOE's Compliance Certification Database (CCD), retrieved 2026-09-19. Among the 414 gas tank models registered at the high draw pattern, this model ranks 236th for lowest energy use. That places it in the second-highest quarter of its class for energy use. If your household draws a different amount of hot water than the test assumes, your gas use will differ from this figure. The registry does not give that amount.

The high draw pattern represents a larger household, or one where showers and laundry overlap. This model's first hour rating, the gallons of hot water available in the first hour from a full tank, is 83 gallons. Its rated volume is 38 gallons. If you are checking whether it fits a home like that, compare these two figures with the home's peak hot-water demand. The 264 therms figure applies only to a home that uses hot water at the high draw pattern. The registry gives no energy figure for a home that uses less. To compare other models in the same class, use the same-class replacement search by model number or the water heater selector by fuel, space and size.

This text does not state the running cost. The cost depends on your state's average residential gas price. The page calculates it from your ZIP code, using the 264 therms figure at the high draw pattern. The gap to the class median described above means this model costs more to run than a median model at any gas rate. The extra cost is the price of 4 therms a year at your rate. To see that difference on your own rate, use the cost calculator for your ZIP code. The steps behind the figure are set out in how the annual cost is calculated. The installed-cost range on this page is a modeled range with its own source and date. It is not a quote.