LOCHINVAR TK-510U-E 2**

This site calculates the 209 therms figure; the registry does not publish it. The calculation uses the registry's UEF, the ratio of hot water delivered to energy used, and a daily hot-water draw. That draw is the one the DOE test sets for the high draw pattern. For this model the UEF is 0.81, and the source is the DOE CCD, retrieved 2026-09-19. Among the 397 gas tankless models registered at the high draw pattern, it ranks 323rd for lowest energy use. That puts it in the highest quarter of its class for energy use. The figure holds only at the test's daily draw. A household using more or less hot water will have a different total. The method behind the annual figure is described on a separate page.

The high draw pattern describes a larger household, or one where showers and laundry overlap. The registry lists this unit's maximum flow rate in gallons per minute as 5. A household that runs several fixtures at once can compare their combined flow with that 5 limit. If your usage matches the high draw pattern, 209 therms works as a reference based on the federal test. A household with lower hot-water use does not match the condition behind that figure, and no figure for lower use is available here. To check a model with lower energy use, you can look up a same-class replacement by model number. Compare any alternative against the class median of 182 therms.

This page does not give the running cost as text. It depends on the average residential gas price in your state, so the page calculates it from your ZIP. The calculation uses this model's 209 therms a year and that local rate. The same rate also applies to the 27 therms gap above the 182 therms class median. The cost of that gap stays unknown until a rate is applied. The running cost calculator for your own ZIP applies your local rate. The installed price range appears in its own block, with its source and date. That range is a modeled installed cost, not a quote.