State GUR 40 4**

It holds 38 gallons in the test, 2 gallons less than its 40-gallon sold size. It delivers 83 gallons of hot water in the test's first hour. That is 45 gallons more than its tank holds, since it reheats during the hour. Among 763 gas storage models, 242 have a higher first-hour rating. The median gas storage model gives 78 gallons in the first hour of the test.

On Oct 26, 2026, this heater was not listed as ENERGY STAR certified. In tests, 64% of the energy it uses ends up as hot water (UEF 0.64). The daily hot water use in the test, called its draw pattern, was high. Its UEF is lower than that of 255 of the 434 gas storage models with its draw pattern. For its type and draw pattern, the UEF runs from 0.61 to 0.90. When it reheats water in the test, 77% of the energy it uses ends up in the water.

It is sold as GS6 40 BCUT* 4**, GSX 40 BCUT* 4**, and GW8 40 BCUT* 4**. Its test figures match those of 9 other basic models. In all, 4 other brands list one or more of them. You can find the whole group on the page for the A. O. Smith G9-UT4040NVR 5**.