Ruud RHE40S

It holds 37 gallons in the test, 3 gallons less than its 40-gallon sold size. Starting full, it gives 87 gallons of hot water in its first hour of use. That is 50 gallons more than its tank holds, since it reheats during the hour. Among 763 gas storage models, 143 have a higher first-hour rating. The median gas storage model gives 78 gallons in its first hour.

It was not listed as ENERGY STAR certified on Oct 26, 2026. In tests, 83% of the energy went to hot water, so its UEF is 0.83. Its test ran at the high level of daily hot water use. Of 434 gas storage models with the same draw pattern, 46 have a higher UEF. A UEF of 0.66 is the median for its type and draw pattern. Of the energy spent to reheat water, 92% goes into it (its recovery efficiency).

There are 3 more basic models with the same test figures. The ECOSENSE, Rheem, and Richmond brands list one or more of them. You can find the whole group on the page for the Rheem RHE40S.

It may qualify for 2 rebate programs.