A. O. SMITH FMHR-40 4**

The figure of 191 therms is not a registry value. This site computed it from the registry's UEF, the ratio of hot water delivered to energy used, which is 0.58 for this model, and from the DOE test's daily hot-water draw for the medium draw pattern. The source is DOE CCD, retrieved 2026-09-19. The comparison group is the 288 models registered as a gas tank at this draw pattern. Within it, this unit sits 6 therms above the class median of 185 therms. Its rank is 231st lowest energy use of 288, which places it in the highest quarter of its class for energy use.

The energy figure applies only to the medium draw pattern, which represents a typical multi-person household on a busy morning. The unit has a first hour rating, the gallons of hot water available in the first hour from a full tank, of 59, and a rated volume of 38 gallons. A household whose use resembles that pattern can compare its own gas bills with 191 therms directly. A household with lighter or heavier use should not expect that figure to hold, because this page gives no annual energy for other draw patterns. Readers who rank models by energy use alone should note that models placed before 231st use less at the same pattern. To compare by fuel, space and size, use the water heater selector.

The running cost is not written in this text because it depends on your state's average residential gas price. The cost calculator takes your ZIP and applies that price to 191 therms of natural gas. The same price can be applied to the class median of 185 therms, so the gap of 6 therms can be read in your own rate. The steps are described in how the annual cost is calculated. The modeled installed-cost range appears in its own block with its source and date, and it is a range, not a quote. If you need a same-class replacement for FMHR-40 4**, you can find one by model number. All comparisons here stay within the medium draw pattern and the 288-model class.