AMERICAN TK-310U-E 2**

The figure of 209 therms is computed by this site, not published by the registry. It combines the registry's UEF, the ratio of hot water delivered to energy used, of 0.81 with the daily hot-water draw that the DOE test assigns to the high draw pattern. The registry also lists a maximum flow rate in gallons per minute of 4.8 for this model. The energy source is DOE CCD, retrieved 2026-09-19. The value applies only to natural gas and only to the high draw pattern. Real use in a given home may differ, and this page does not estimate it. The steps behind the calculation are described in how the annual cost is calculated.

Among the 397 models registered as a gas tankless unit at the high draw pattern, this one ranks 323rd lowest in energy use. Its 209 therms is 27 therms above the class median of 182 therms, which places it in the highest quarter of its class for energy use. The high draw pattern describes a larger household, or one where showers and laundry overlap, so the comparison fits that case. It applies less well if your household's hot-water use matches a different draw pattern, because the figure was not computed for that pattern. To look at other units in the same class, use a same-class replacement search by model number.

Running cost is not stated in the text because it depends on the average residential gas price in your state. The page computes it from your ZIP for the 209 therms at the high draw pattern. The cost calculator on your own ZIP applies the same rate to any other figure, including the 27 therms gap to the class median of 182 therms. The installed price range appears in its own block with its source and date. It is a modeled range, not a quote, and it is not repeated here. Measured use in your home is not available, since the 209 therms reflects only the federal test's daily draw. For a different fuel, space or size, the selector by fuel, space and size starts from those inputs.