A. O. SMITH GUF-50 1**

The figure of 242 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 0.7 for this model, and from the DOE test's daily hot-water draw for the high draw pattern. The source is DOE CCD, retrieved 2026-09-19. Among 414 gas tank models at the same draw pattern, this unit sits 18 therms below the class median of 260 therms. Its rank is 90th lowest energy use of 414, which places it in the lowest quarter of its class. The steps of the calculation are set out on the methodology page.

This model has a rated volume of 48 gallons and a first hour rating, the gallons of hot water available in the first hour from a full tank, of 83 gallons. The high draw pattern describes a larger household, or one where showers and laundry overlap, so the energy figure fits readers whose use resembles that. It does not describe a smaller household with lighter use, because the figure is tied to the test draw and not to actual use. Energy use at other draw patterns is not available for this model on this page. Whether the first hour rating covers a specific household is not assessed here. Readers still choosing between fuels or sizes can use the water heater selector, which filters by fuel, space and size.

Running cost is not stated here because it depends on the state average residential gas price, and that differs by reader. The 242 therms figure applies to natural gas at the high draw pattern, so it becomes a cost only when multiplied by a natural gas rate. The cost calculator applies the rate for your own ZIP to this figure. The modeled installed-cost range appears in its own block with its source and date, and this text does not repeat it. To compare against another unit of the same class, find a same-class replacement by model number. The 18 therms gap to the 260 therms median is a difference in test-draw energy, not a measured saving in any particular home.