LOCHINVAR TK-310CX3 1**

The energy figure on this page is not taken directly from the registry. This site computed it from the registry's UEF, the ratio of hot water delivered to energy used, which is 0.81 for this unit, and from the DOE test's daily hot-water draw for the high draw pattern. The result is 209 therms of natural gas a year, from DOE CCD data retrieved 2026-09-19. Among the 397 models registered as a gas tankless unit at the high draw pattern, this one ranks 323rd lowest in energy use. That puts it in the highest quarter of its class for energy use, 27 therms above the class median of 182 therms.

The high draw pattern describes a larger household, or one where showers and laundry overlap. The 4.7 figure is the maximum flow rate in gallons per minute, the highest flow the registry lists for this unit. For a household that matches that pattern and needs that flow, 209 therms is the figure to check. A reader whose main concern is low gas use should note that the model sits 27 therms above the 182 therms median. The figure applies only to the high draw pattern, and annual energy at other draw patterns is not available on this page. To compare other options, use the water heater selector or find a same-class replacement by model number.

The running cost is not written in this text because it depends on your state's average residential gas price, which is not part of the registry data. The cost calculator applies your ZIP to the 209 therms figure for this model. The same 209 therms at a different gas price gives a different yearly cost, and the 27 therms gap to the class median changes with the price too. The calculation method explains how the annual cost is worked out. The modeled installed-cost range appears in its own block with its source and date, and it is not a quote. Actual gas use in your home is not available from this data and may differ from the federal test's draw.