AMERICAN GUF-40 1**

The registry lists a UEF, the ratio of hot water delivered to energy used, of 0.65 for this model. The registry itself does not state the annual energy figure. This site computed 171 therms from that UEF and the DOE test's daily hot-water draw for the medium draw pattern. The medium draw pattern is a typical three- or four-person household. The figure applies only at that draw. A household with a different draw will use a different amount of gas, and that value is not available. The source is DOE CCD, retrieved 2026-09-19.

Among the 288 models registered as a gas tank at the medium draw pattern, this model has the 33rd lowest energy use. That places it in the lowest quarter of its class for energy use. Its 171 therms is 14 therms below the class median of 185 therms. The comparison covers energy use only. Capacity is rated separately. The first hour rating, the gallons of hot water available in the first hour from a full tank, is 68 gallons for this model. Its rated volume is 38 gallons. The energy rank does not show whether that first hour rating meets a household's peak demand. It suits a reader comparing gas tank models at the medium draw pattern. It does not suit a reader whose household draw differs from that pattern.

Running cost is not written here because it depends on your state's average residential gas price. Enter your ZIP in the cost calculator to apply that price to 171 therms. The methodology page explains how the annual cost is calculated. The therm total stays the same at the medium draw pattern; only the price per therm changes the cost. The price is a state average, so it may differ from your own utility bill. To find a same-class unit, use the replacement search by model number with GUF-40 1**. The water heater selector filters by fuel, space and size instead.