RELIANCE WATER HEATERS TK-510U-I 2**

The 209 therms figure 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, with the DOE test's daily hot-water draw. For this model the UEF is 0.81, taken from DOE CCD data retrieved 2026-09-19. The result holds only at the test's daily draw for the high draw pattern. A household drawing more or less hot water will use more or less gas. Among the 397 gas tankless models at the high draw pattern, it ranks 323rd lowest in energy use. That places it in the highest quarter of its class for energy use. The steps behind the figure are set out in how the annual cost is calculated.

The high draw pattern describes a larger household, or one where showers and laundry overlap. The unit's maximum flow rate in gallons per minute is 5, as listed in the registry. Whether that covers a given home depends on how many fixtures run at once, which the registry does not record. Energy figures for this model at a smaller household's draw pattern are not available here. At the test's draw, the 27 therms gap above the 182 therms median means this model uses more gas than a median unit in its class. The data does not show how the unit performs outside the test's conditions. Units at the same draw pattern can be compared through a same-class replacement search by model number.

Running cost is not stated in this text. It depends on the reader's state average residential natural gas price, applied to the 209 therms figure at the high draw pattern. The page computes it from the reader's ZIP rather than estimating it here. The cost calculator on your own ZIP shows that result. The 27 therms difference from the class median works the same way: at any given gas price, the extra cost scales with that gap. The installed-price range appears in its own block, with its source and date, as a modeled range rather than a quote. What a specific installer would charge is not available in this data.