STATE TK-510C-NI 1**

The 209 therms figure is computed by this site, not taken from the registry. It combines the unit'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. The registry lists a UEF of 0.81 for this model, from DOE CCD data retrieved 2026-09-19. The result holds only at that test draw. A home that uses more or less hot water than the test assumes will use a different amount of gas. The class compared here is the 397 models registered as a gas tankless unit at the high draw pattern. 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 registry lists a maximum flow rate in gallons per minute of 4.7 for this model. Whether that flow covers the fixtures a given home runs at the same time is not available in this data. At 209 therms against the class median of 182 therms, the model sits in the highest quarter of its class for energy use. A home with a lighter daily draw is not what this figure describes, so the figure should not be applied to it. To check other models registered in the same class, use the same-class replacement search by model number.

The running cost is not stated in this text, because it depends on your state's average residential gas price. The page computes it from your ZIP in its own block. The 27 therms gap to the class median applies only at the federal test draw, and its cost follows from the same local rate. A change in your gas rate moves the cost, while the 209 therms figure stays the same at the test draw. The installed price range shown on the page is a modeled range with its own source and date, not a quote. A price from a specific installer is not available here. To run the figure on your own rate, use the cost calculator on your own ZIP.