State FMHR-40 4**

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 59 gallons in the test (its first-hour rating). Its tank holds 38 gallons, so reheating adds 21 gallons during the first hour. Among 763 gas storage models, 705 have a higher first-hour rating. Among gas storage models, the median first-hour rating is 78 gallons.

On Oct 26, 2026, this heater was not listed as ENERGY STAR certified. In tests, 58% of the energy it uses ends up as hot water (UEF 0.58). Its test ran at the medium level of daily hot water use. Of 288 gas storage models with the same draw pattern, 230 have a higher UEF and 11 a lower one. For its type and draw pattern, the UEF runs from 0.57 to 0.75. Of the energy spent to reheat water, 78% goes into it (its recovery efficiency).

It is the basic model for GS6-40-MHG 4** and SCI-40-MHG 4**. All of its test figures are shared by 4 other basic models. They are listed under 4 other brands, one each. For the full group, see the A. O. Smith FMHR-40 4** page.