RELIANCE WATER HEATERS GCF-40 1**

It holds 38 gallons in the test, 2 gallons less than its 40-gallon sold size. Over one hour from a full tank, it gave 70 gallons in the test (its first-hour rating). Its tank holds 38 gallons, so reheating adds 32 gallons during the first hour. Among 763 gas storage models, 510 have a higher first-hour rating. Among gas storage models, the median first-hour rating is 78 gallons.

As of Oct 26, 2026, it was not listed as ENERGY STAR certified. In tests, 64% of the energy it uses ends up as hot water (UEF 0.64). Its test ran at the medium level of daily hot water use. Its UEF is lower than that of 43 of the 288 gas storage models with its draw pattern. For its type and draw pattern, the UEF runs from 0.57 to 0.75. When it reheats water in the test, 73% of the energy it uses ends up in the water.

A tag or quote may show any of its 4 model numbers. All of its test figures are shared by 5 other basic models. They are listed under 5 other brands, one each. For the full group, see the A. O. Smith GCF-40 1** page.

It may qualify for one rebate program.