STATE T-H3M-OS-N 1**

The registry lists a UEF, the ratio of hot water delivered to energy used, of 0.91 for this unit. Its maximum flow rate in gallons per minute is 3.5. The annual figure of 122 therms of natural gas is not a registry entry. This site computed it from the registry's UEF and the DOE test's daily hot-water draw for the medium draw pattern, which represents a typical household on a busy morning. The energy data comes from DOE CCD, retrieved 2026-09-19. The figure holds only at that draw pattern. A household that uses more or less hot water than the test assumes will use a different amount of gas, and this page does not estimate that amount.

Against its class, the unit has the 4th lowest energy use of 80 models registered as a gas tankless unit at the medium draw pattern. The class median is 135 therms, so this unit sits 13 therms below it. The comparison covers only that class and that draw pattern. It says nothing about other fuel types or other heater types. The figure suits a reader whose household resembles the medium draw pattern and who wants to verify the energy use against a same-class comparison. It suits less well a reader whose hot-water use differs from that pattern, or who needs a peak flow above 3.5 gallons per minute. To compare other models by fuel, space and size, use the water heater selector.

The running cost is not stated here because it depends on the state average residential gas price, which differs by reader. Multiply 122 therms by your own rate per therm, or enter your ZIP in the cost calculator, which applies that price. The steps behind the annual figure are described in the methodology for water heater costs. The 13 therms gap to the class median of 135 therms carries the same condition, so any cost difference depends on that same rate. The modeled installed-cost range appears in its own block on this page with its source and date. To check a unit of the same class against this one, find a replacement by model number.