Ruud RHE40SP

It holds 37 gallons in the test, 3 gallons less than its 40-gallon sold size. Starting full, it gives 68 gallons of hot water in its first hour of use. That is 31 gallons more than its tank holds, since it reheats during the hour. In the first hour, 529 of the 763 gas storage models give more hot water. Among gas storage models, the median first-hour rating is 78 gallons.

It was not listed as ENERGY STAR certified on Oct 26, 2026. In tests, 75% of the energy it uses ends up as hot water (UEF 0.75). In the test, daily hot water use was set to medium (its draw pattern). Of 288 gas storage models with the same draw pattern, none has a higher UEF. A UEF of 0.60 is the median for its type and draw pattern. Of the energy spent to reheat water, 87% goes into it (its recovery efficiency).

Its test figures match those of 3 other basic models. Of those, one or more are under the ECOSENSE, Rheem, and Richmond brands. You can find the whole group on the page for the Rheem RHE40SP.

It may qualify for 2 rebate programs in 2 states.