LOCHINVAR TK-310U-E 2**

The figure of 209 therms of natural gas is computed by this site, not published by the registry. It applies the registry's UEF, the ratio of hot water delivered to energy used, which is 0.81 for this model, to the DOE test's daily hot-water draw for the high draw pattern. The source is the DOE CCD, retrieved 2026-09-19. The result holds only under those test conditions, and a household's real use will differ with how much hot water it actually draws. The maximum flow rate in gallons per minute is 4.8. That value describes capacity and does not enter the annual figure.

Among the 397 models registered as a gas tankless unit at the high draw pattern, this unit ranks 323rd lowest for energy use. It sits 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. A reader in that situation who weighs other features first may accept this position. A reader who puts low gas use first should note the rank of 323rd lowest of 397 and can compare options with the water heater selector or find a same-class replacement by model number. The registry data used here does not rate any other feature of the unit.

Running cost is not stated as an amount on this page because it depends on your state's average residential gas price. Multiplying 209 therms by that price, in matching units, gives a yearly cost at the test's draw. The 27 therms gap to the class median scales by the same price. The cost calculator applies the price for your own ZIP, and how the annual cost is calculated sets out the steps. The modeled installed-cost range appears in its own block with its source and date, so it is not repeated here. Neither figure is a quote, and the energy data was retrieved on 2026-09-19.