LOCHINVAR TK-310U-I 2**

This site computes the 209 therms figure; the registry does not publish it. 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 the high draw pattern. This unit's UEF is 0.81, from the DOE CCD, retrieved 2026-09-19. The figure holds only at the federal test's daily draw. A home that uses more hot water than that draw will use more gas, and a home that uses less will use less. The steps behind the figure are set out in how the annual cost is calculated. If a plumber or seller quotes a different yearly figure, check which draw pattern and which UEF they used before comparing it with 209 therms.

The high draw pattern describes a larger household, or one where showers and laundry overlap. This unit's maximum flow rate in gallons per minute is 4.7. The comparison class is the 397 models registered as a gas tankless unit at the high draw pattern. Within that class, its 209 therms sits 27 therms above the 182 therms median. That makes it 323rd lowest in energy use of 397, which is in the highest quarter of its class for energy use. A reader who ranks yearly gas use first will find that most models in this class use less. To compare this model with others at the same draw pattern, use the same-class replacement finder by model number.

The text on this page gives no running cost. The yearly cost of 209 therms depends on your state's average residential natural gas price, so the page works it out from your ZIP. The cost calculator on your own ZIP applies that rate to this model's use at the high draw pattern. The 27 therms gap to the class median becomes a cost gap only at your own rate, so this text cannot give its size. The installed price range appears in its own block with its source and date. That range is modeled from data and is not a quote.