RELIANCE WATER HEATERS GCFL-40 1**

The registry lists a UEF, the ratio of hot water delivered to energy used, of 0.66 for this model. This site turns that UEF into 168 therms a year by applying the DOE test's daily hot-water draw for the medium draw pattern. The inputs come from the DOE CCD, retrieved 2026-09-19, and the annual figure is not a registry value. Against the 288 gas tank models registered at the medium draw pattern, the median is 185 therms. This model sits 17 therms below it, at 27th lowest energy use of 288. That places it in the lowest quarter of its class for energy use. The method behind the annual figure is documented separately.

The first hour rating, the gallons of hot water available in the first hour from a full tank, is 65. The rated volume is 38 gallons. The 168 therms figure applies only to a household whose hot-water use matches the medium draw pattern. A household that draws more hot water than the test assumes will use more gas than that. This page has no annual figure for the other draw patterns of this model. Whether 65 gallons of first hour rating and 38 gallons of storage cover a busy hour is not something this data settles. Households comparing fuel, space and size can use the water heater selector to narrow the options.

The running cost is not stated here because it depends on the state average residential gas price. The cost calculator for your own ZIP applies that price to 168 therms. The result holds only at the medium draw pattern, so a home with different hot-water use will see a different cost. The 17 therms gap to the class median of 185 therms is a gas quantity, and its cost changes with the price you pay. The installed price range is shown in its own block, with its source and date. It is a modeled range, not a quote. Rank 27th of 288 describes energy use only, not price.